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      <link href="/javanblog/2021/04/25/SpringMVC/"/>
      <url>/javanblog/2021/04/25/SpringMVC/</url>
      
        <content type="html"><![CDATA[<h1 id="Spring-MVC"><a href="#Spring-MVC" class="headerlink" title="Spring MVC"></a>Spring MVC</h1><h2 id="1-什么是Spirng-MVC"><a href="#1-什么是Spirng-MVC" class="headerlink" title="1 什么是Spirng MVC"></a>1 什么是Spirng MVC</h2><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201201212217243.png" alt="image-20201201212217243"></p><blockquote><p>概述</p></blockquote><p>Spirng MVC是Spring Framework的一部分，是基于java实现MVC的轻量级Web框架。</p><p>官方文档：<a href="https://docs.spring.io/spring-framework/docs/current/reference/html/web.html">https://docs.spring.io/spring-framework/docs/current/reference/html/web.html</a></p><p>为什么要学习Spring MVC？</p><p>Spring MVC 特点</p><ul><li>轻量级，简单易学</li><li>高效，基于请求响应的MVC框架</li><li>与 Spring 兼容性好，无缝结合</li><li>约定大于配置</li><li>功能强大，RESTful，数据验证，格式化，本地化，主题等</li><li>简洁灵活</li></ul><p>Spring MVC的web框架围绕<strong>DispatcherServlet</strong> [ 调度Servlet ] 设计。</p><p>DispatcherServlet的作用是将请求分发到不同的处理器。从Spring 2.5开始，使用Java 5或者以上版本的用户可以采用基于注解形式进行开发，十分简洁。</p><p><strong>最重要的一点还是用的人多 , 使用的公司多 。</strong></p><blockquote><p>中心控制器</p></blockquote><p>Spring MVC框架像许多其他MVC框架一样, <strong>以请求为驱动</strong> , <strong>围绕一个中心Servlet分派请求及提供其他功能</strong>，**DispatcherServlet是一个实际的Servlet (它继承自HttpServlet 基类)**。</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201201213059093.png" alt="image-20201201213059093"></p><p>SpringMVC的原理如下图所示：</p><p>当发起请求时被前置的控制器拦截到请求，根据请求参数生成代理请求，找到请求对应的实际控制器，控制器处理请求，创建数据模型，访问数据库，将模型响应给中心控制器，控制器使用模型与视图渲染视图结果，将结果返回给中心控制器，再将结果返回给请求者。</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201201213349055.png" alt="image-20201201213349055"></p><blockquote><p>Spring MVC 执行原理</p></blockquote><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201201213630465.png" alt="image-20201201213630465"></p><p>图为SpringMVC的一个较完整的流程图，实线表示SpringMVC框架提供的技术，不需要开发者实现，虚线表示需要开发者实现。</p><p><strong>执行流程：</strong></p><ol><li><p>DispatcherServlet表示前置控制器，是整个SpringMVC的控制中心。用户发出请求，DispatcherServlet接收请求并拦截请求。</p><p>我们假设请求的url为 : <a href="http://localhost:8080/SpringMVC/hello">http://localhost:8080/SpringMVC/hello</a></p><p><strong>如上url拆分成三部分：</strong></p><p><a href="http://localhost:8080服务器域名">http://localhost:8080服务器域名</a></p><p>SpringMVC部署在服务器上的web站点</p><p>hello表示控制器</p><p>通过分析，如上url表示为：请求位于服务器localhost:8080上的SpringMVC站点的hello控制器。</p></li><li><p>HandlerMapping为处理器映射。DispatcherServlet调用HandlerMapping,HandlerMapping根据请求url查找Handler。</p></li><li><p>HandlerExecution表示具体的Handler,其主要作用是根据url查找控制器，如上url被查找控制器为：hello。</p></li><li><p>HandlerExecution将解析后的信息传递给DispatcherServlet,如解析控制器映射等。返回HandlerExecutionChain对象给中央控制器，封装了HandlerIntercepter（处理器拦截器）、Handler（处理器对象）</p></li><li><p>HandlerAdapter表示处理器适配器，其按照特定的规则去执行Handler。</p></li><li><p>Handler让具体的Controller执行。</p></li><li><p>Controller将具体的执行信息返回给HandlerAdapter,如ModelAndView。</p></li><li><p>HandlerAdapter将视图逻辑名或模型传递给DispatcherServlet。</p></li><li><p>DispatcherServlet调用视图解析器(ViewResolver)来解析HandlerAdapter传递的逻辑视图名。</p></li><li><p>视图解析器将解析的逻辑视图名传给DispatcherServlet。</p></li><li><p>DispatcherServlet根据视图解析器解析的视图结果填充数据，调用具体的视图。</p></li><li><p>最终视图呈现给用户。</p></li></ol><h2 id="2-第一个MVC程序"><a href="#2-第一个MVC程序" class="headerlink" title="2 第一个MVC程序"></a>2 第一个MVC程序</h2><p>1、创建Maven父项目，然后删除src文件，在pom.xml中添加依赖。</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">dependencies</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>junit<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>junit<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">version</span>&gt;</span>4.12<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>org.springframework<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>spring-webmvc<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">version</span>&gt;</span>5.2.0.RELEASE<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>javax.servlet<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>servlet-api<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">version</span>&gt;</span>2.5<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>javax.servlet.jsp<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>jsp-api<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">version</span>&gt;</span>2.2<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br><span class="line">    <span class="comment">&lt;!--EL表达式标签支持--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>javax.servlet<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>jstl<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">version</span>&gt;</span>1.2<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">dependencies</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>2、新建一个Module，Maven工程，名为springmvc-02-hello，添加web框架支持！</p><p>3、正常来说需要配置Spring MVC 依赖，由于我们在父工程中配置了，所以此处可以省略。</p><p>4、配置web.xml文件，注册DispatcherServlet。</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8"?&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">web-app</span> <span class="attr">xmlns</span>=<span class="string">"http://xmlns.jcp.org/xml/ns/javaee"</span></span></span><br><span class="line"><span class="tag">         <span class="attr">xmlns:xsi</span>=<span class="string">"http://www.w3.org/2001/XMLSchema-instance"</span></span></span><br><span class="line"><span class="tag">         <span class="attr">xsi:schemaLocation</span>=<span class="string">"http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"</span></span></span><br><span class="line"><span class="tag">         <span class="attr">version</span>=<span class="string">"4.0"</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--1 配置DispatcherServlet--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">servlet</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">servlet-name</span>&gt;</span>DispatcherServlet<span class="tag">&lt;/<span class="name">servlet-name</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">servlet-class</span>&gt;</span>org.springframework.web.servlet.DispatcherServlet<span class="tag">&lt;/<span class="name">servlet-class</span>&gt;</span></span><br><span class="line">        <span class="comment">&lt;!--关联一个springmvc配置文件：【servlet-name】-servlet.xml--&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">init-param</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">param-name</span>&gt;</span>contextConfigLocation<span class="tag">&lt;/<span class="name">param-name</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">param-value</span>&gt;</span>classpath:springmvc-servlet.xml<span class="tag">&lt;/<span class="name">param-value</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">init-param</span>&gt;</span></span><br><span class="line">        <span class="comment">&lt;!--设置启动级别，1表是跟随服务器启动--&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">load-on-startup</span>&gt;</span>1<span class="tag">&lt;/<span class="name">load-on-startup</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">servlet</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">servlet-mapping</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">servlet-name</span>&gt;</span>DispatcherServlet<span class="tag">&lt;/<span class="name">servlet-name</span>&gt;</span></span><br><span class="line">        <span class="comment">&lt;!--/ 匹配所有请求，不包括.jsp--&gt;</span></span><br><span class="line">        <span class="comment">&lt;!--/* 匹配所有请求，包括.jsp--&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">url-pattern</span>&gt;</span>/<span class="tag">&lt;/<span class="name">url-pattern</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">servlet-mapping</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">web-app</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>5、编写Spring MVC 的配置文件！，名称springmvc-servlet.xml：【servletname】-servlet.xml</p><p>名称要求按照官方的来。</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8"?&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">beans</span> <span class="attr">xmlns</span>=<span class="string">"http://www.springframework.org/schema/beans"</span></span></span><br><span class="line"><span class="tag">      <span class="attr">xmlns:xsi</span>=<span class="string">"http://www.w3.org/2001/XMLSchema-instance"</span></span></span><br><span class="line"><span class="tag">      <span class="attr">xsi:schemaLocation</span>=<span class="string">"http://www.springframework.org/schema/beans</span></span></span><br><span class="line"><span class="tag"><span class="string">       http://www.springframework.org/schema/beans/spring-beans.xsd"</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">beans</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>6、添加处理器映射器</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">bean</span> <span class="attr">class</span>=<span class="string">"org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping"</span>/&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>7、添加处理器适配器</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">bean</span> <span class="attr">class</span>=<span class="string">"org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter"</span>/&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>8、添加视图解析器</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!--视图解析器:DispatcherServlet给他的ModelAndView--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">bean</span> <span class="attr">class</span>=<span class="string">"org.springframework.web.servlet.view.InternalResourceViewResolver"</span> <span class="attr">id</span>=<span class="string">"InternalResourceViewResolver"</span>&gt;</span></span><br><span class="line">   <span class="comment">&lt;!--前缀--&gt;</span></span><br><span class="line">   <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"prefix"</span> <span class="attr">value</span>=<span class="string">"/WEB-INF/jsp/"</span>/&gt;</span></span><br><span class="line">   <span class="comment">&lt;!--后缀--&gt;</span></span><br><span class="line">   <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"suffix"</span> <span class="attr">value</span>=<span class="string">".jsp"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">bean</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>9、编写操作业务的Controller，要么实现Controller接口，要么增加注解；需要返回一个ModelAndView，装数据，封视图。</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.controller;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> org.springframework.web.servlet.ModelAndView;</span><br><span class="line"><span class="keyword">import</span> org.springframework.web.servlet.mvc.Controller;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> javax.servlet.http.HttpServletRequest;</span><br><span class="line"><span class="keyword">import</span> javax.servlet.http.HttpServletResponse;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 3 编写控制器</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">TestController</span> <span class="keyword">implements</span> <span class="title">Controller</span> </span>{</span><br><span class="line">    <span class="function"><span class="keyword">public</span> ModelAndView <span class="title">handleRequest</span><span class="params">(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse)</span> <span class="keyword">throws</span> Exception </span>{</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 创建模型视图</span></span><br><span class="line">        ModelAndView mv = <span class="keyword">new</span> ModelAndView();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 调用业务层</span></span><br><span class="line">        String msg = <span class="string">"HelloSpringMVC"</span>;</span><br><span class="line">        <span class="comment">// 封装对象，放在ModelAndView中,model</span></span><br><span class="line">        mv.addObject(<span class="string">"msg"</span>, msg);</span><br><span class="line">        <span class="comment">// 封装要跳转的视图，放在ModelAndView中,view</span></span><br><span class="line">        mv.setViewName(<span class="string">"test"</span>);</span><br><span class="line"></span><br><span class="line">        <span class="keyword">return</span> mv;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>10、Controller交给SpringIOC容器，即在Spring MVC 配置文件中注册bean</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!--编写好控制器之后，需要在springmvc的配置文件中注册bean--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">bean</span> <span class="attr">id</span>=<span class="string">"/test"</span> <span class="attr">class</span>=<span class="string">"com.zzb.controller.TestController"</span>/&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>11 、写要跳转的jsp页面，显示ModelandView存放的数据，以及正常页面。</p><figure class="highlight jsp"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">&lt;%@ page contentType=<span class="string">"text/html;charset=UTF-8"</span> language=<span class="string">"java"</span> %&gt;</span><br><span class="line">&lt;html&gt;</span><br><span class="line">&lt;head&gt;</span><br><span class="line">    &lt;title&gt;Title&lt;/title&gt;</span><br><span class="line">&lt;/head&gt;</span><br><span class="line">&lt;body&gt;</span><br><span class="line">${msg}</span><br><span class="line">&lt;/body&gt;</span><br><span class="line">&lt;/html&gt;</span><br><span class="line"></span><br></pre></td></tr></tbody></table></figure><p>12、配置Tomcat，启动测试！</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201201215723607.png" alt="image-20201201215723607"></p><p><strong>注意：</strong></p><p><strong>可能遇到的问题：访问出现404，排查步骤：</strong></p><ol><li>查看控制台输出，看一下是不是缺少了什么jar包。</li><li>如果jar包存在，显示无法输出，就在IDEA的项目发布中，添加lib依赖！</li><li>重启Tomcat 即可解决！</li></ol><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201201215830687.png" alt="image-20201201215830687"></p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201201215952561.png" alt="image-20201201215952561"></p><p><strong>使用注解开发</strong></p><p>1、新建一个Module，<strong>springmvc-03-hello-annotation</strong>，添加web支持，配置Tomcat，如上一步添加jar包。</p><p>2、在pom.xml文件引入相关的依赖：主要有Spring框架核心库、Spring MVC、servlet , JSTL等。我们在父依赖中已经引入了！</p><p>3、配置web.xml文件，注册DispatcherServlet</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8"?&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">web-app</span> <span class="attr">xmlns</span>=<span class="string">"http://xmlns.jcp.org/xml/ns/javaee"</span></span></span><br><span class="line"><span class="tag">         <span class="attr">xmlns:xsi</span>=<span class="string">"http://www.w3.org/2001/XMLSchema-instance"</span></span></span><br><span class="line"><span class="tag">         <span class="attr">xsi:schemaLocation</span>=<span class="string">"http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"</span></span></span><br><span class="line"><span class="tag">         <span class="attr">version</span>=<span class="string">"4.0"</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--1 配置DispatcherServlet--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">servlet</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">servlet-name</span>&gt;</span>DispatcherServlet<span class="tag">&lt;/<span class="name">servlet-name</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">servlet-class</span>&gt;</span>org.springframework.web.servlet.DispatcherServlet<span class="tag">&lt;/<span class="name">servlet-class</span>&gt;</span></span><br><span class="line">        <span class="comment">&lt;!--关联一个springmvc配置文件：【servlet-name】-servlet.xml--&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">init-param</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">param-name</span>&gt;</span>contextConfigLocation<span class="tag">&lt;/<span class="name">param-name</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">param-value</span>&gt;</span>classpath:springmvc-servlet.xml<span class="tag">&lt;/<span class="name">param-value</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">init-param</span>&gt;</span></span><br><span class="line">        <span class="comment">&lt;!--设置启动级别，1表是跟随服务器启动--&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">load-on-startup</span>&gt;</span>1<span class="tag">&lt;/<span class="name">load-on-startup</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">servlet</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">servlet-mapping</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">servlet-name</span>&gt;</span>DispatcherServlet<span class="tag">&lt;/<span class="name">servlet-name</span>&gt;</span></span><br><span class="line">        <span class="comment">&lt;!--/ 匹配所有请求，不包括.jsp--&gt;</span></span><br><span class="line">        <span class="comment">&lt;!--/* 匹配所有请求，包括.jsp--&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">url-pattern</span>&gt;</span>/<span class="tag">&lt;/<span class="name">url-pattern</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">servlet-mapping</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">web-app</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>注意事项：</p><ul><li>注意web.xml版本问题，要最新版！</li><li>注册DispatcherServlet</li><li>关联SpringMVC的配置文件</li><li>启动级别为1</li><li>映射路径为 / 【不要用/*，会404】</li></ul><p>4、添加Spring MVC配置文件</p><p>在resource目录下添加springmvc-servlet.xml配置文件，配置的形式与Spring容器配置基本类似，为了支持基于注解的IOC，设置了自动扫描包的功能，具体配置信息如下：</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8"?&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">beans</span> <span class="attr">xmlns</span>=<span class="string">"http://www.springframework.org/schema/beans"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xmlns:xsi</span>=<span class="string">"http://www.w3.org/2001/XMLSchema-instance"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xmlns:context</span>=<span class="string">"http://www.springframework.org/schema/context"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xmlns:mvc</span>=<span class="string">"http://www.springframework.org/schema/mvc"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xsi:schemaLocation</span>=<span class="string">"http://www.springframework.org/schema/beans</span></span></span><br><span class="line"><span class="tag"><span class="string">       http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/mvc https://www.springframework.org/schema/mvc/spring-mvc.xsd"</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--自动扫描包，让指定包下的注解生效，由IOC容器统一管理--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">context:component-scan</span> <span class="attr">base-package</span>=<span class="string">"com.zzb.controller"</span>/&gt;</span></span><br><span class="line">    <span class="comment">&lt;!--让Spring MVC不处理静态资源，例如.mp3 .css .jpg等不走视图解析器--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">mvc:default-servlet-handler</span>/&gt;</span></span><br><span class="line">    <span class="comment">&lt;!--</span></span><br><span class="line"><span class="comment">       支持mvc注解驱动</span></span><br><span class="line"><span class="comment">       在spring中一般采用@RequestMapping注解来完成映射关系</span></span><br><span class="line"><span class="comment">       要想使@RequestMapping注解生效</span></span><br><span class="line"><span class="comment">       必须向上下文中注册DefaultAnnotationHandlerMapping</span></span><br><span class="line"><span class="comment">       和一个AnnotationMethodHandlerAdapter实例</span></span><br><span class="line"><span class="comment">       这两个实例分别在类级别和方法级别处理。</span></span><br><span class="line"><span class="comment">       而annotation-driven配置帮助我们自动完成上述两个实例的注入</span></span><br><span class="line"><span class="comment">    --&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">mvc:annotation-driven</span>/&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--视图解析器--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">bean</span> <span class="attr">class</span>=<span class="string">"org.springframework.web.servlet.view.InternalResourceViewResolver"</span> <span class="attr">id</span>=<span class="string">"InternalResourceViewResolver"</span>&gt;</span></span><br><span class="line">        <span class="comment">&lt;!--前缀--&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"prefix"</span> <span class="attr">value</span>=<span class="string">"/WEB-INF/jsp/"</span>/&gt;</span></span><br><span class="line">        <span class="comment">&lt;!--后缀--&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"suffix"</span> <span class="attr">value</span>=<span class="string">".jsp"</span>/&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">bean</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">beans</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>在视图解析器中我们把所有的视图都存放在/WEB-INF/目录下，这样可以保证视图安全，因为这个目录下的文件，客户端不能直接访问。</p><p>上述Spring MVC的配置文件主要完成了以下工作：</p><ul><li>让IOC的注解生效</li><li>静态资源过滤 ：HTML . JS . CSS . 图片 ， 视频 …..</li><li>MVC的注解驱动</li><li>配置视图解析器</li></ul><p>5、创建Controller</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.controller;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> org.springframework.stereotype.Controller;</span><br><span class="line"><span class="keyword">import</span> org.springframework.ui.Model;</span><br><span class="line"><span class="keyword">import</span> org.springframework.web.bind.annotation.RequestMapping;</span><br><span class="line"></span><br><span class="line"><span class="meta">@Controller</span></span><br><span class="line"><span class="meta">@RequestMapping("/HelloController")</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">HelloController</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="meta">@RequestMapping("/hello")</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">hello</span><span class="params">(Model model)</span></span>{</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 封装数据</span></span><br><span class="line">        model.addAttribute(<span class="string">"msg"</span>, <span class="string">"Hello, Spring MVC Annotation!"</span>);</span><br><span class="line">        <span class="comment">// 返回的字符串会被视图解析器解析</span></span><br><span class="line">        <span class="keyword">return</span> <span class="string">"hello"</span>;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><ul><li>@Controller是为了让Spring IOC容器初始化时自动扫描到；</li><li>@RequestMapping是为了映射请求路径，这里因为类与方法上都有映射所以访问时应该是/HelloController/hello；</li><li>方法中声明Model类型的参数是为了把Action中的数据带到视图中；</li><li>方法返回的结果是视图的名称hello，加上配置文件中的前后缀变成WEB-INF/jsp/<strong>hello</strong>.jsp。</li></ul><p>6、创建视图层</p><ol><li><p>在WEB-INF/ jsp目录中创建hello.jsp ， 视图可以直接取出并展示从Controller带回的信息；</p></li><li><p>可以通过EL表达式取出Model中存放的值，或者对象。</p></li><li><p>```jsp<br>&lt;%@ page contentType=”text/html;charset=UTF-8” language=”java” %&gt;</p>    <title>Title</title>${msg}<figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">7、配置Tomcat，启动运行</span><br><span class="line"></span><br><span class="line">1. ![image-20201203225601938](https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201203225601938.png)</span><br><span class="line"></span><br><span class="line">**总结：**</span><br><span class="line"></span><br><span class="line">实现步骤其实非常的简单：</span><br><span class="line"></span><br><span class="line">1. 新建一个web项目</span><br><span class="line">2. 导入相关jar包</span><br><span class="line">3. 编写web.xml , 注册DispatcherServlet</span><br><span class="line">4. 编写springmvc配置文件</span><br><span class="line">5. 接下来就是去创建对应的控制类 , controller</span><br><span class="line">6. 最后完善前端视图和controller之间的对应</span><br><span class="line">7. 测试运行调试.</span><br><span class="line">8. 使用springMVC必须配置的三大件：**处理器映射器、处理器适配器、视图解析器**</span><br><span class="line">9. 通常，我们只需要**手动配置视图解析器**，而**处理器映射器**和**处理器适配器**只需要开启**注解驱动**即可，而省去了大段的xml配置</span><br><span class="line"></span><br><span class="line">## 3 Controller（控制器）和RestFul风格</span><br><span class="line"></span><br><span class="line">**控制器Controller**</span><br><span class="line"></span><br><span class="line">- 控制器负责提供访问应用程序的行为，通常通过接口定义或注解定义两种方法实现。</span><br><span class="line">- 控制器负责解析用户的请求并将其转换为一个模型。</span><br><span class="line">- 在Spring MVC中一个控制器类可以包含多个方法。</span><br><span class="line">- 在Spring MVC中，对于Controller的配置方式有很多种。</span><br><span class="line"></span><br><span class="line">module：springmvc-04-controller</span><br><span class="line"></span><br><span class="line">&gt; 环境搭建</span><br><span class="line"></span><br><span class="line">**添加web框架支持，以及Artifacts中的lib配置！**</span><br><span class="line"></span><br><span class="line">web.xml</span><br><span class="line"></span><br><span class="line">```xml</span><br><span class="line">&lt;?xml version="1.0" encoding="UTF-8"?&gt;</span><br><span class="line">&lt;web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"</span><br><span class="line">         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"</span><br><span class="line">         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"</span><br><span class="line">         version="4.0"&gt;</span><br><span class="line"></span><br><span class="line">    &lt;!--1 配置DispatcherServlet--&gt;</span><br><span class="line">    &lt;servlet&gt;</span><br><span class="line">         &lt;servlet-name&gt;DispatcherServlet&lt;/servlet-name&gt;</span><br><span class="line">         &lt;servlet-class&gt;org.springframework.web.servlet.DispatcherServlet&lt;/servlet-class&gt;</span><br><span class="line">         &lt;init-param&gt;</span><br><span class="line">             &lt;param-name&gt;contextConfigLocation&lt;/param-name&gt;</span><br><span class="line">             &lt;param-value&gt;classpath:springmvc-servlet.xml&lt;/param-value&gt;</span><br><span class="line">         &lt;/init-param&gt;</span><br><span class="line">         &lt;load-on-startup&gt;1&lt;/load-on-startup&gt;</span><br><span class="line">    &lt;/servlet&gt;</span><br><span class="line">    &lt;servlet-mapping&gt;</span><br><span class="line">        &lt;servlet-name&gt;DispatcherServlet&lt;/servlet-name&gt;</span><br><span class="line">        &lt;url-pattern&gt;/&lt;/url-pattern&gt;</span><br><span class="line">    &lt;/servlet-mapping&gt;</span><br><span class="line"></span><br><span class="line">&lt;/web-app&gt;</span><br></pre></td></tr></tbody></table></figure></li></ol><p>springmvc-servlet.xml</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8"?&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">beans</span> <span class="attr">xmlns</span>=<span class="string">"http://www.springframework.org/schema/beans"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xmlns:xsi</span>=<span class="string">"http://www.w3.org/2001/XMLSchema-instance"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xmlns:context</span>=<span class="string">"http://www.springframework.org/schema/context"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xmlns:mvc</span>=<span class="string">"http://www.springframework.org/schema/mvc"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xsi:schemaLocation</span>=<span class="string">"http://www.springframework.org/schema/beans</span></span></span><br><span class="line"><span class="tag"><span class="string">       http://www.springframework.org/schema/beans/spring-beans.xsd</span></span></span><br><span class="line"><span class="tag"><span class="string">       http://www.springframework.org/schema/context</span></span></span><br><span class="line"><span class="tag"><span class="string">       https://www.springframework.org/schema/context/spring-context.xsd</span></span></span><br><span class="line"><span class="tag"><span class="string">       http://www.springframework.org/schema/mvc</span></span></span><br><span class="line"><span class="tag"><span class="string">       https://www.springframework.org/schema/mvc/spring-mvc.xsd"</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--自动扫描包，让指定包下的注解生效，由IOC容器统一管理--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">context:component-scan</span> <span class="attr">base-package</span>=<span class="string">"com.zzb.controller"</span>/&gt;</span></span><br><span class="line">    <span class="comment">&lt;!--让Spring MVC不处理静态资源，例如.mp3 .css .jpg等不走视图解析器--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">mvc:default-servlet-handler</span>/&gt;</span></span><br><span class="line">    <span class="comment">&lt;!--</span></span><br><span class="line"><span class="comment">       支持mvc注解驱动</span></span><br><span class="line"><span class="comment">       在spring中一般采用@RequestMapping注解来完成映射关系</span></span><br><span class="line"><span class="comment">       要想使@RequestMapping注解生效</span></span><br><span class="line"><span class="comment">       必须向上下文中注册DefaultAnnotationHandlerMapping</span></span><br><span class="line"><span class="comment">       和一个AnnotationMethodHandlerAdapter实例</span></span><br><span class="line"><span class="comment">       这两个实例分别在类级别和方法级别处理。</span></span><br><span class="line"><span class="comment">       而annotation-driven配置帮助我们自动完成上述两个实例的注入</span></span><br><span class="line"><span class="comment">    --&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">mvc:annotation-driven</span>/&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--视图解析器--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">bean</span> <span class="attr">class</span>=<span class="string">"org.springframework.web.servlet.view.InternalResourceViewResolver"</span> <span class="attr">id</span>=<span class="string">"InternalResourceViewResolver"</span>&gt;</span></span><br><span class="line">        <span class="comment">&lt;!--前缀--&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"prefix"</span> <span class="attr">value</span>=<span class="string">"/WEB-INF/jsp/"</span>/&gt;</span></span><br><span class="line">        <span class="comment">&lt;!--后缀--&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"suffix"</span> <span class="attr">value</span>=<span class="string">".jsp"</span>/&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">bean</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">beans</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><blockquote><p>代码实现</p></blockquote><h3 id="实现Controller接口"><a href="#实现Controller接口" class="headerlink" title="实现Controller接口"></a>实现Controller接口</h3><p>Controller是一个接口，在org.springframework.web.servlet.mvc包下，接口中只有一个方法；</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@FunctionalInterface</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">Controller</span> </span>{</span><br><span class="line">    <span class="meta">@Nullable</span></span><br><span class="line">    <span class="function">ModelAndView <span class="title">handleRequest</span><span class="params">(HttpServletRequest var1, HttpServletResponse var2)</span> <span class="keyword">throws</span> Exception</span>;</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>1、编写一个ControllerTest1类，实现Contoller接口</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.controller;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> org.springframework.web.servlet.ModelAndView;</span><br><span class="line"><span class="keyword">import</span> org.springframework.web.servlet.mvc.Controller;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> javax.servlet.http.HttpServletRequest;</span><br><span class="line"><span class="keyword">import</span> javax.servlet.http.HttpServletResponse;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">ControllerTest1</span> <span class="keyword">implements</span> <span class="title">Controller</span> </span>{</span><br><span class="line">    <span class="function"><span class="keyword">public</span> ModelAndView <span class="title">handleRequest</span><span class="params">(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse)</span> <span class="keyword">throws</span> Exception </span>{</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 创建模型视图</span></span><br><span class="line">        ModelAndView modelAndView = <span class="keyword">new</span> ModelAndView();</span><br><span class="line">        <span class="comment">// 调用业务层</span></span><br><span class="line">        String msg = <span class="string">"ControllerTest1"</span>;</span><br><span class="line">        modelAndView.addObject(<span class="string">"msg"</span>, msg);</span><br><span class="line">        <span class="comment">// 设置跳转视图</span></span><br><span class="line">        modelAndView.setViewName(<span class="string">"test"</span>);</span><br><span class="line"></span><br><span class="line">        <span class="keyword">return</span> modelAndView;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>2、去Spring配置文件中注册请求的bean，name或id对应请求路径，class对应处理请求的类</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">bean</span> <span class="attr">id</span>=<span class="string">"/t1"</span> <span class="attr">class</span>=<span class="string">"com.zzb.controller.ControllerTest1"</span>/&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>3、编写前端展示页面test.jsp，注意在WEB-INF/jsp目录</p><figure class="highlight jsp"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">&lt;%@ page contentType=<span class="string">"text/html;charset=UTF-8"</span> language=<span class="string">"java"</span> %&gt;</span><br><span class="line">&lt;html&gt;</span><br><span class="line">&lt;head&gt;</span><br><span class="line">    &lt;title&gt;Title&lt;/title&gt;</span><br><span class="line">&lt;/head&gt;</span><br><span class="line">&lt;body&gt;</span><br><span class="line">${msg}</span><br><span class="line">&lt;/body&gt;</span><br><span class="line">&lt;/html&gt;</span><br><span class="line"></span><br></pre></td></tr></tbody></table></figure><p>4、配置Tomcat，启动测试！</p><p>测试结果：</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201211145922123.png" alt="image-20201211145922123"></p><p><strong>说明：</strong></p><ul><li>实现Controller接口定义控制器的方法比较老了，一般不推荐使用！</li><li>缺点是一个控制器只有一个方法，如果要多个方法则需要定义多个Controller。</li></ul><h3 id="使用注解-Controller"><a href="#使用注解-Controller" class="headerlink" title="使用注解@Controller"></a>使用注解@Controller</h3><ul><li><p>@Controller注解类型用于声明Spring类的实例是一个控制器（在讲IOC时还提到了另外3个注解）；</p></li><li><p>Spring可以使用扫描机制来找到应用程序中所有基于注解的控制器类，为了保证Spring能找到你的控制器，需要在配置文件中声明组件扫描。</p></li></ul><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!--自动扫描包，让指定包下的注解生效，由IOC容器统一管理--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">context:component-scan</span> <span class="attr">base-package</span>=<span class="string">"com.zzb.controller"</span>/&gt;</span></span><br></pre></td></tr></tbody></table></figure><ul><li>增加一个ControllerTest2类，使用注解！</li></ul><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.controller;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> org.springframework.stereotype.Controller;</span><br><span class="line"><span class="keyword">import</span> org.springframework.ui.Model;</span><br><span class="line"><span class="keyword">import</span> org.springframework.web.bind.annotation.RequestMapping;</span><br><span class="line"></span><br><span class="line"><span class="meta">@Controller</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">ControllerTest2</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="meta">@RequestMapping("/t2")</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">test2</span><span class="params">(Model model)</span></span>{</span><br><span class="line"></span><br><span class="line">        model.addAttribute(<span class="string">"msg"</span>, <span class="string">"ControllerTest2"</span>);</span><br><span class="line">        <span class="comment">// 返回视图位置</span></span><br><span class="line">        <span class="keyword">return</span> <span class="string">"test"</span>;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><ul><li>启动Tomcat测试</li></ul><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201211151124229.png" alt="image-20201211151124229"></p><p><strong>可以发现，我们的两个请求都可以指向一个视图，但是页面结果的结果是不一样的，从这里可以看出视图是被复用的，而控制器与视图之间是弱偶合关系。</strong></p><p><strong>注解方式是平时使用的最多的方式！</strong></p><h3 id="RequestMapping"><a href="#RequestMapping" class="headerlink" title="RequestMapping"></a>RequestMapping</h3><p><strong>@RequestMapping</strong></p><p>@RequestMapping注解用于映射url到控制器类或一个特定的处理程序方法。可用于类或方法上。用于类上，表示类中的所有响应请求的方法都是以该地址作为父路径。</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.controller;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> org.springframework.stereotype.Controller;</span><br><span class="line"><span class="keyword">import</span> org.springframework.ui.Model;</span><br><span class="line"><span class="keyword">import</span> org.springframework.web.bind.annotation.RequestMapping;</span><br><span class="line"></span><br><span class="line"><span class="meta">@Controller</span></span><br><span class="line"><span class="meta">@RequestMapping("/myweb")</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">ControllerTest2</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="meta">@RequestMapping("/t2")</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">test2</span><span class="params">(Model model)</span></span>{</span><br><span class="line"></span><br><span class="line">        model.addAttribute(<span class="string">"msg"</span>, <span class="string">"ControllerTest2"</span>);</span><br><span class="line">        <span class="comment">// 返回视图位置</span></span><br><span class="line">        <span class="keyword">return</span> <span class="string">"test"</span>;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201211151426583.png" alt="image-20201211151426583"></p><p><strong>注意观察url</strong></p><h3 id="RestFul-风格"><a href="#RestFul-风格" class="headerlink" title="RestFul 风格"></a>RestFul 风格</h3><p><strong>概念</strong></p><p>Restful就是一个资源定位及资源操作的风格。不是标准也不是协议，只是一种风格。基于这个风格设计的软件可以更简洁，更有层次，更易于实现缓存等机制。</p><p><strong>功能</strong></p><p>资源：互联网所有的事物都可以被抽象为资源</p><p>资源操作：使用POST、DELETE、PUT、GET，使用不同方法对资源进行操作。</p><p>分别对应 添加、 删除、修改、查询。</p><p><strong>传统方式操作资源</strong>  ：通过不同的参数来实现不同的效果！方法单一，post 和 get</p><p>​    <a href="http://127.0.0.1/item/queryItem.action?id=1">http://127.0.0.1/item/queryItem.action?id=1</a> 查询,GET</p><p>​    <a href="http://127.0.0.1/item/saveItem.action">http://127.0.0.1/item/saveItem.action</a> 新增,POST</p><p>​    <a href="http://127.0.0.1/item/updateItem.action">http://127.0.0.1/item/updateItem.action</a> 更新,POST</p><p>​    <a href="http://127.0.0.1/item/deleteItem.action?id=1">http://127.0.0.1/item/deleteItem.action?id=1</a> 删除,GET或POST</p><p><strong>使用RESTful操作资源</strong> ：可以通过不同的请求方式来实现不同的效果！如下：请求地址一样，但是功能可以不同！</p><p>​    <a href="http://127.0.0.1/item/1">http://127.0.0.1/item/1</a> 查询,GET</p><p>​    <a href="http://127.0.0.1/item">http://127.0.0.1/item</a> 新增,POST</p><p>​    <a href="http://127.0.0.1/item">http://127.0.0.1/item</a> 更新,PUT</p><p>​    <a href="http://127.0.0.1/item/1">http://127.0.0.1/item/1</a> 删除,DELETE</p><blockquote><p>代码实现</p></blockquote><p>1、新建一个RestFulController</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.controller;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> org.springframework.stereotype.Controller;</span><br><span class="line"></span><br><span class="line"><span class="meta">@Controller</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">RestFulController</span> </span>{</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>2、在Spring MVC中可以使用  @PathVariable 注解，让方法参数的值对应绑定到一个URI模板变量上。</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.controller;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> org.springframework.stereotype.Controller;</span><br><span class="line"><span class="keyword">import</span> org.springframework.ui.Model;</span><br><span class="line"><span class="keyword">import</span> org.springframework.web.bind.annotation.PathVariable;</span><br><span class="line"><span class="keyword">import</span> org.springframework.web.bind.annotation.RequestMapping;</span><br><span class="line"></span><br><span class="line"><span class="meta">@Controller</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">RestFulController</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="meta">@RequestMapping("/t3/{p1}/{p2}")</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">test3</span><span class="params">(<span class="meta">@PathVariable</span> <span class="keyword">int</span> p1,<span class="meta">@PathVariable</span> <span class="keyword">int</span> p2, Model model)</span></span>{</span><br><span class="line"></span><br><span class="line">        <span class="keyword">int</span> result = p1 + p2;</span><br><span class="line"></span><br><span class="line">        model.addAttribute(<span class="string">"msg"</span>, result);</span><br><span class="line"></span><br><span class="line">        <span class="keyword">return</span> <span class="string">"test"</span>;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>3、测试</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201211193901159.png" alt="image-20201211193901159"></p><p><strong>使用路径变量的好处？</strong></p><ul><li><p>使路径变得更加简洁；</p></li><li><p>获得参数更加方便，框架会自动进行类型转换；</p></li><li><p>通过路径变量的类型可以约束访问参数，如果类型不一样，则访问不到对应的请求方法，如这里访问是的路径是/t3/1/a，则路径与方法不匹配，而不会是参数转换失败。</p></li></ul><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201211194058094.png" alt="image-20201211194058094"></p><p>4、修改参数类型，再次测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.controller;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> org.springframework.stereotype.Controller;</span><br><span class="line"><span class="keyword">import</span> org.springframework.ui.Model;</span><br><span class="line"><span class="keyword">import</span> org.springframework.web.bind.annotation.PathVariable;</span><br><span class="line"><span class="keyword">import</span> org.springframework.web.bind.annotation.RequestMapping;</span><br><span class="line"></span><br><span class="line"><span class="meta">@Controller</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">RestFulController</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="meta">@RequestMapping("/t3/{p1}/{p2}")</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">test3</span><span class="params">(<span class="meta">@PathVariable</span> <span class="keyword">int</span> p1,<span class="meta">@PathVariable</span> String p2, Model model)</span></span>{</span><br><span class="line"></span><br><span class="line">        String result = p1 + p2;</span><br><span class="line"></span><br><span class="line">        model.addAttribute(<span class="string">"msg"</span>, result);</span><br><span class="line"></span><br><span class="line">        <span class="keyword">return</span> <span class="string">"test"</span>;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>测试结果：</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201211194249908.png" alt="image-20201211194249908"></p><p><strong>使用method属性指定请求类型</strong></p><p>用于约束请求的类型，可以收窄请求范围。指定请求谓词的类型如GET, POST, HEAD, OPTIONS, PUT, PATCH, DELETE, TRACE等</p><p>测试：</p><p>1、增加一个方法</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 映射访问路径，必须是post请求</span></span><br><span class="line"><span class="meta">@RequestMapping(value = "/t4", method = {RequestMethod.POST})</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> String <span class="title">test4</span><span class="params">(Model model)</span></span>{</span><br><span class="line"></span><br><span class="line">    model.addAttribute(<span class="string">"msg"</span>, <span class="string">"Hello"</span>);</span><br><span class="line">    <span class="keyword">return</span> <span class="string">"test"</span>;</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>2、使用浏览器地址栏进行访问默认是Get请求，会报错405</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201211194724167.png" alt="image-20201211194724167"></p><p>3、将指定方法从POST改为GET</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@RequestMapping(value = "/t4", method = {RequestMethod.GET})</span></span><br></pre></td></tr></tbody></table></figure><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201211195054151.png" alt="image-20201211195054151"></p><p><strong>总结：</strong></p><p>Spring MVC 的 @RequestMapping 注解能够处理 HTTP 请求的方法, 比如 GET, PUT, POST, DELETE 以及 PATCH。</p><p><strong>所有的地址栏请求默认都会是 HTTP GET 类型的。</strong></p><p>方法级别的注解变体有如下几个：组合注解</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@GetMapping</span></span><br><span class="line"><span class="meta">@PostMapping</span></span><br><span class="line"><span class="meta">@PutMapping</span></span><br><span class="line"><span class="meta">@DeleteMapping</span></span><br><span class="line"><span class="meta">@PatchMapping</span></span><br></pre></td></tr></tbody></table></figure><p>@GetMapping 是一个组合注解，平时使用的会比较多！</p><p>它所扮演的是 @RequestMapping(method =RequestMethod.GET) 的一个快捷方式。</p><h2 id="4-数据处理及跳转"><a href="#4-数据处理及跳转" class="headerlink" title="4 数据处理及跳转"></a>4 数据处理及跳转</h2><h3 id="结果跳转方式"><a href="#结果跳转方式" class="headerlink" title="结果跳转方式"></a>结果跳转方式</h3><p><strong>ModelAndView</strong></p><p>设置 ModelAndView 对象，根据 View 的名称和视图解析器跳转到指定的页面</p><p>页面 : {视图解析器前缀} + viewName +{视图解析器后缀}</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!--视图解析器--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">bean</span> <span class="attr">class</span>=<span class="string">"org.springframework.web.servlet.view.InternalResourceViewResolver"</span> <span class="attr">id</span>=<span class="string">"InternalResourceViewResolver"</span>&gt;</span></span><br><span class="line">    <span class="comment">&lt;!--前缀--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"prefix"</span> <span class="attr">value</span>=<span class="string">"/WEB-INF/jsp/"</span>/&gt;</span></span><br><span class="line">    <span class="comment">&lt;!--后缀--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"suffix"</span> <span class="attr">value</span>=<span class="string">".jsp"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">bean</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>对应的Controller类</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.controller;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> org.springframework.web.servlet.ModelAndView;</span><br><span class="line"><span class="keyword">import</span> org.springframework.web.servlet.mvc.Controller;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> javax.servlet.http.HttpServletRequest;</span><br><span class="line"><span class="keyword">import</span> javax.servlet.http.HttpServletResponse;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">ControllerTest1</span> <span class="keyword">implements</span> <span class="title">Controller</span> </span>{</span><br><span class="line">    <span class="function"><span class="keyword">public</span> ModelAndView <span class="title">handleRequest</span><span class="params">(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse)</span> <span class="keyword">throws</span> Exception </span>{</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 创建模型视图</span></span><br><span class="line">        ModelAndView modelAndView = <span class="keyword">new</span> ModelAndView();</span><br><span class="line">        <span class="comment">// 调用业务层</span></span><br><span class="line">        String msg = <span class="string">"ControllerTest1"</span>;</span><br><span class="line">        modelAndView.addObject(<span class="string">"msg"</span>, msg);</span><br><span class="line">        <span class="comment">// 设置跳转视图</span></span><br><span class="line">        modelAndView.setViewName(<span class="string">"test"</span>);</span><br><span class="line"></span><br><span class="line">        <span class="keyword">return</span> modelAndView;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><strong>ServletAPI</strong></p><p>通过设置ServletAPI，不需要视图解析器</p><p>1、通过HttpServletResponse进行输出</p><p>2、通过HttpServletResponse实现重定向</p><p>3、通过HttpServletRequest实现转发</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.controller;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> org.springframework.stereotype.Controller;</span><br><span class="line"><span class="keyword">import</span> org.springframework.web.bind.annotation.RequestMapping;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> javax.servlet.ServletException;</span><br><span class="line"><span class="keyword">import</span> javax.servlet.http.HttpServletRequest;</span><br><span class="line"><span class="keyword">import</span> javax.servlet.http.HttpServletResponse;</span><br><span class="line"><span class="keyword">import</span> java.io.IOException;</span><br><span class="line"></span><br><span class="line"><span class="meta">@Controller</span></span><br><span class="line"><span class="meta">@RequestMapping("/t3")</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">ControllerTest3</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="meta">@RequestMapping("/t1")</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">test1</span><span class="params">(HttpServletRequest req, HttpServletResponse resp)</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"></span><br><span class="line">        resp.getWriter().println(<span class="string">"Hello,Spring BY servlet API"</span>);</span><br><span class="line"></span><br><span class="line">    }</span><br><span class="line">    <span class="meta">@RequestMapping("/t2")</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">test2</span><span class="params">(HttpServletRequest req, HttpServletResponse resp)</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line">        <span class="comment">// 重定向</span></span><br><span class="line">        resp.sendRedirect(req.getContextPath() + <span class="string">"/index.jsp"</span>);</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="meta">@RequestMapping("/t3")</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">test3</span><span class="params">(HttpServletRequest req, HttpServletResponse resp)</span> <span class="keyword">throws</span> ServletException, IOException </span>{</span><br><span class="line">        <span class="comment">// 转发</span></span><br><span class="line">        req.setAttribute(<span class="string">"msg"</span>, <span class="string">"/t3/t3"</span>);</span><br><span class="line">        req.getRequestDispatcher(<span class="string">"/WEB-INF/jsp/test.jsp"</span>).forward(req, resp);</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><strong>Spring MVC</strong></p><p>通过 Spring MVC 来实现转发和重定向——不需要视图解析器。</p><p>注意：测试前先将视图解析器注释掉。</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.controller;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> org.springframework.stereotype.Controller;</span><br><span class="line"><span class="keyword">import</span> org.springframework.web.bind.annotation.RequestMapping;</span><br><span class="line"></span><br><span class="line"><span class="meta">@Controller</span></span><br><span class="line"><span class="meta">@RequestMapping("/t4")</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">ControllerTest4</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="meta">@RequestMapping("/t1")</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">test1</span><span class="params">()</span></span>{</span><br><span class="line">        <span class="comment">// 转发</span></span><br><span class="line">        <span class="keyword">return</span> <span class="string">"/index.jsp"</span>;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="meta">@RequestMapping("/t2")</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">test2</span><span class="params">()</span></span>{</span><br><span class="line">        <span class="comment">// 显示转发</span></span><br><span class="line">        <span class="keyword">return</span> <span class="string">"forward:/index.jsp"</span>;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="meta">@RequestMapping("/t3")</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">test3</span><span class="params">()</span></span>{</span><br><span class="line">        <span class="comment">// 重定向</span></span><br><span class="line">        <span class="keyword">return</span> <span class="string">"redirect:/index.jsp"</span>;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>通过 Spring MVC 来实现转发和重定向——使用视图解析器。</p><p>注意：开启视图解析器。</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.controller;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> org.springframework.stereotype.Controller;</span><br><span class="line"><span class="keyword">import</span> org.springframework.web.bind.annotation.RequestMapping;</span><br><span class="line"></span><br><span class="line"><span class="meta">@Controller</span></span><br><span class="line"><span class="meta">@RequestMapping("/t5")</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">ControllerTest5</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="meta">@RequestMapping("/t1")</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">test1</span><span class="params">()</span></span>{</span><br><span class="line">        <span class="comment">// 转发</span></span><br><span class="line">        <span class="keyword">return</span> <span class="string">"test"</span>;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="meta">@RequestMapping("/t2")</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">test2</span><span class="params">()</span></span>{</span><br><span class="line">        <span class="comment">// 重定向</span></span><br><span class="line">        <span class="keyword">return</span> <span class="string">"redirect:/index.jsp"</span>;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><h3 id="数据处理"><a href="#数据处理" class="headerlink" title="数据处理"></a>数据处理</h3><p><strong>处理提交数据</strong></p><p>1、提交的域名数据名称和处理方法的参数名一致</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.controller;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> com.zzb.pojo.User;</span><br><span class="line"><span class="keyword">import</span> org.springframework.stereotype.Controller;</span><br><span class="line"><span class="keyword">import</span> org.springframework.ui.Model;</span><br><span class="line"><span class="keyword">import</span> org.springframework.web.bind.annotation.RequestMapping;</span><br><span class="line"></span><br><span class="line"><span class="meta">@Controller</span></span><br><span class="line"><span class="meta">@RequestMapping("/data")</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">DataController</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 域名参数与控制器参数名一致的情况</span></span><br><span class="line">    <span class="meta">@RequestMapping("/t1")</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">test1</span><span class="params">(String name, Model model)</span></span>{</span><br><span class="line">        <span class="comment">// 1 接收前端参数</span></span><br><span class="line">        System.out.println(name);</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 2 将数据返回给前端</span></span><br><span class="line">        model.addAttribute(<span class="string">"msg"</span>, name);</span><br><span class="line">        <span class="keyword">return</span> <span class="string">"test"</span>;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>测试结果：</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201215161547471.png" alt="image-20201215161547471"></p><p>2、提交的域名数据名称和处理方法的参数名不一致</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 域名参数与控制器参数名不一致的情况</span></span><br><span class="line"><span class="meta">@RequestMapping("/t2")</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> String <span class="title">test2</span><span class="params">(<span class="meta">@RequestParam("username")</span> String name, Model model)</span></span>{</span><br><span class="line">    <span class="comment">// 1 接受前端参数</span></span><br><span class="line">    System.out.println(name);</span><br><span class="line">    <span class="comment">// 2 将参数传递给前端展示</span></span><br><span class="line">    model.addAttribute(<span class="string">"msg"</span>, name);</span><br><span class="line">    <span class="keyword">return</span> <span class="string">"test"</span>;</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>测试结果：</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201215161656888.png" alt="image-20201215161656888"></p><p>3、参数是一个对象</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.pojo;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">User</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span>  <span class="keyword">int</span> id;</span><br><span class="line">    <span class="keyword">private</span>  String name;</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">int</span> age;</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="title">User</span><span class="params">()</span> </span>{</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="title">User</span><span class="params">(<span class="keyword">int</span> id, String name, <span class="keyword">int</span> age)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.id = id;</span><br><span class="line">        <span class="keyword">this</span>.name = name;</span><br><span class="line">        <span class="keyword">this</span>.age = age;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">getId</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> id;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setId</span><span class="params">(<span class="keyword">int</span> id)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.id = id;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">getName</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> name;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setName</span><span class="params">(String name)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.name = name;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">getAge</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> age;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setAge</span><span class="params">(<span class="keyword">int</span> age)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.age = age;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">toString</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> <span class="string">"User{"</span> +</span><br><span class="line">                <span class="string">"id="</span> + id +</span><br><span class="line">                <span class="string">", name='"</span> + name + <span class="string">'\''</span> +</span><br><span class="line">                <span class="string">", age="</span> + age +</span><br><span class="line">                <span class="string">'}'</span>;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 前端提交的参数是一个对象</span></span><br><span class="line"><span class="meta">@RequestMapping("/t3")</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> String <span class="title">test3</span><span class="params">(User user, Model model)</span></span>{</span><br><span class="line">    <span class="comment">// 1 接收前端传递的参数</span></span><br><span class="line">    System.out.println(user.toString());</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 2 将参数传递给前端页面展示</span></span><br><span class="line">    model.addAttribute(<span class="string">"msg"</span>, user.toString());</span><br><span class="line">    <span class="keyword">return</span> <span class="string">"test"</span>;</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>测试结果：</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201215161837158.png" alt="image-20201215161837158"></p><p>注意：如果传递参数是对象的话，前端传递的参数名和对象的属性名必须一致，否则为null。</p><p><strong>前端展示数据</strong></p><p>1、ModelAndView</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.controller;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> org.springframework.web.servlet.ModelAndView;</span><br><span class="line"><span class="keyword">import</span> org.springframework.web.servlet.mvc.Controller;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> javax.servlet.http.HttpServletRequest;</span><br><span class="line"><span class="keyword">import</span> javax.servlet.http.HttpServletResponse;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">ControllerTest1</span> <span class="keyword">implements</span> <span class="title">Controller</span> </span>{</span><br><span class="line">    <span class="function"><span class="keyword">public</span> ModelAndView <span class="title">handleRequest</span><span class="params">(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse)</span> <span class="keyword">throws</span> Exception </span>{</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 创建模型视图</span></span><br><span class="line">        ModelAndView modelAndView = <span class="keyword">new</span> ModelAndView();</span><br><span class="line">        <span class="comment">// 调用业务层</span></span><br><span class="line">        String msg = <span class="string">"ControllerTest1"</span>;</span><br><span class="line">        modelAndView.addObject(<span class="string">"msg"</span>, msg);</span><br><span class="line">        <span class="comment">// 设置跳转视图</span></span><br><span class="line">        modelAndView.setViewName(<span class="string">"test"</span>);</span><br><span class="line"></span><br><span class="line">        <span class="keyword">return</span> modelAndView;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>2、ModelMap</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@RequestMapping("/t1")</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> String <span class="title">test1</span><span class="params">(String name, ModelMap modelMap)</span></span>{</span><br><span class="line">    <span class="comment">// 1 接收前端参数</span></span><br><span class="line">    System.out.println(name);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 2 将数据返回给前端</span></span><br><span class="line">    modelMap.addAttribute(<span class="string">"msg"</span>, name);</span><br><span class="line">    <span class="keyword">return</span> <span class="string">"test"</span>;</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>3、Model</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@RequestMapping("/t1")</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> String <span class="title">test1</span><span class="params">(String name, Model model)</span></span>{</span><br><span class="line">    <span class="comment">// 1 接收前端参数</span></span><br><span class="line">    System.out.println(name);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 2 将数据返回给前端</span></span><br><span class="line">    model.addAttribute(<span class="string">"msg"</span>, name);</span><br><span class="line">    <span class="keyword">return</span> <span class="string">"test"</span>;</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>3种方法对比：</p><ul><li><p>Model 只有寥寥几个方法只适合用于储存数据，简化了新手对于Model对象的操作和理解；</p></li><li><p>ModelMap 继承了 LinkedMap ，除了实现了自身的一些方法，同样的继承 LinkedMap 的方法和特性；</p></li><li><p>ModelAndView 可以在储存数据的同时，可以进行设置返回的逻辑视图，进行控制展示层的跳转。</p></li></ul><p><strong>乱码问题</strong></p><p>1、在index.jsp页面写一个表单</p><figure class="highlight"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">&lt;%@ page contentType=<span class="string">"text/html;charset=UTF-8"</span> language=<span class="string">"java"</span> %&gt;</span><br><span class="line">&lt;html&gt;</span><br><span class="line">  &lt;head&gt;</span><br><span class="line">    &lt;title&gt;$Title$&lt;/title&gt;</span><br><span class="line">  &lt;/head&gt;</span><br><span class="line">  &lt;body&gt;</span><br><span class="line">  &lt;form action=${pageContext.request.contextPath}/data/t1 method=<span class="string">"post"</span>&gt;</span><br><span class="line">    &lt;input type=<span class="string">"text"</span> name=<span class="string">"name"</span>&gt;</span><br><span class="line">    &lt;input type=<span class="string">"submit"</span>&gt;</span><br><span class="line">  &lt;/form&gt;</span><br><span class="line">  &lt;/body&gt;</span><br><span class="line">&lt;/html&gt;</span><br></pre></td></tr></tbody></table></figure><p>2、后端处理程序</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Controller</span></span><br><span class="line"><span class="meta">@RequestMapping("/data")</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">DataController</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 域名参数与控制器参数名一致的情况</span></span><br><span class="line">    <span class="meta">@RequestMapping("/t1")</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">test1</span><span class="params">(String name, Model model)</span></span>{</span><br><span class="line">        <span class="comment">// 1 接收前端参数</span></span><br><span class="line">        System.out.println(name);</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 2 将数据返回给前端</span></span><br><span class="line">        model.addAttribute(<span class="string">"msg"</span>, name);</span><br><span class="line">        <span class="keyword">return</span> <span class="string">"test"</span>;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>3、输入中文 哈哈哈 测试</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201215163654829.png" alt="image-20201215163654829"></p><p>乱码问题通过过滤器解决，Spring MVC 提供了一个过滤器，需要在web.xml中配置！</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">filter</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">filter-name</span>&gt;</span>encoding<span class="tag">&lt;/<span class="name">filter-name</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">filter-class</span>&gt;</span>org.springframework.web.filter.CharacterEncodingFilter<span class="tag">&lt;/<span class="name">filter-class</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">init-param</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">param-name</span>&gt;</span>encoding<span class="tag">&lt;/<span class="name">param-name</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">param-value</span>&gt;</span>utf-8<span class="tag">&lt;/<span class="name">param-value</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">init-param</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">filter</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">filter-mapping</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">filter-name</span>&gt;</span>encoding<span class="tag">&lt;/<span class="name">filter-name</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">url-pattern</span>&gt;</span>/*<span class="tag">&lt;/<span class="name">url-pattern</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">filter-mapping</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201215164057192.png" alt="image-20201215164057192"></p><p>自定义过滤器：</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br><span class="line">106</span><br><span class="line">107</span><br><span class="line">108</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.filter;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> javax.servlet.*;</span><br><span class="line"><span class="keyword">import</span> javax.servlet.http.HttpServletRequest;</span><br><span class="line"><span class="keyword">import</span> javax.servlet.http.HttpServletRequestWrapper;</span><br><span class="line"><span class="keyword">import</span> javax.servlet.http.HttpServletResponse;</span><br><span class="line"><span class="keyword">import</span> java.io.IOException;</span><br><span class="line"><span class="keyword">import</span> java.io.UnsupportedEncodingException;</span><br><span class="line"><span class="keyword">import</span> java.util.Map;</span><br><span class="line"></span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment">* 解决get和post请求 全部乱码的过滤器</span></span><br><span class="line"><span class="comment">*/</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">GenericEncodingFilter</span> <span class="keyword">implements</span> <span class="title">Filter</span> </span>{</span><br><span class="line"></span><br><span class="line">   <span class="meta">@Override</span></span><br><span class="line">   <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">destroy</span><span class="params">()</span> </span>{</span><br><span class="line">  }</span><br><span class="line"></span><br><span class="line">   <span class="meta">@Override</span></span><br><span class="line">   <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">doFilter</span><span class="params">(ServletRequest request, ServletResponse response, FilterChain chain)</span> <span class="keyword">throws</span> IOException, ServletException </span>{</span><br><span class="line">       <span class="comment">//处理response的字符编码</span></span><br><span class="line">       HttpServletResponse myResponse=(HttpServletResponse) response;</span><br><span class="line">       myResponse.setContentType(<span class="string">"text/html;charset=UTF-8"</span>);</span><br><span class="line"></span><br><span class="line">       <span class="comment">// 转型为与协议相关对象</span></span><br><span class="line">       HttpServletRequest httpServletRequest = (HttpServletRequest) request;</span><br><span class="line">       <span class="comment">// 对request包装增强</span></span><br><span class="line">       HttpServletRequest myrequest = <span class="keyword">new</span> MyRequest(httpServletRequest);</span><br><span class="line">       chain.doFilter(myrequest, response);</span><br><span class="line">  }</span><br><span class="line"></span><br><span class="line">   <span class="meta">@Override</span></span><br><span class="line">   <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">init</span><span class="params">(FilterConfig filterConfig)</span> <span class="keyword">throws</span> ServletException </span>{</span><br><span class="line">  }</span><br><span class="line"></span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">//自定义request对象，HttpServletRequest的包装类</span></span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">MyRequest</span> <span class="keyword">extends</span> <span class="title">HttpServletRequestWrapper</span> </span>{</span><br><span class="line"></span><br><span class="line">   <span class="keyword">private</span> HttpServletRequest request;</span><br><span class="line">   <span class="comment">//是否编码的标记</span></span><br><span class="line">   <span class="keyword">private</span> <span class="keyword">boolean</span> hasEncode;</span><br><span class="line">   <span class="comment">//定义一个可以传入HttpServletRequest对象的构造函数，以便对其进行装饰</span></span><br><span class="line">   <span class="function"><span class="keyword">public</span> <span class="title">MyRequest</span><span class="params">(HttpServletRequest request)</span> </span>{</span><br><span class="line">       <span class="keyword">super</span>(request);<span class="comment">// super必须写</span></span><br><span class="line">       <span class="keyword">this</span>.request = request;</span><br><span class="line">  }</span><br><span class="line"></span><br><span class="line">   <span class="comment">// 对需要增强方法 进行覆盖</span></span><br><span class="line">   <span class="meta">@Override</span></span><br><span class="line">   <span class="function"><span class="keyword">public</span> Map <span class="title">getParameterMap</span><span class="params">()</span> </span>{</span><br><span class="line">       <span class="comment">// 先获得请求方式</span></span><br><span class="line">       String method = request.getMethod();</span><br><span class="line">       <span class="keyword">if</span> (method.equalsIgnoreCase(<span class="string">"post"</span>)) {</span><br><span class="line">           <span class="comment">// post请求</span></span><br><span class="line">           <span class="keyword">try</span> {</span><br><span class="line">               <span class="comment">// 处理post乱码</span></span><br><span class="line">               request.setCharacterEncoding(<span class="string">"utf-8"</span>);</span><br><span class="line">               <span class="keyword">return</span> request.getParameterMap();</span><br><span class="line">          } <span class="keyword">catch</span> (UnsupportedEncodingException e) {</span><br><span class="line">               e.printStackTrace();</span><br><span class="line">          }</span><br><span class="line">      } <span class="keyword">else</span> <span class="keyword">if</span> (method.equalsIgnoreCase(<span class="string">"get"</span>)) {</span><br><span class="line">           <span class="comment">// get请求</span></span><br><span class="line">           Map&lt;String, String[]&gt; parameterMap = request.getParameterMap();</span><br><span class="line">           <span class="keyword">if</span> (!hasEncode) { <span class="comment">// 确保get手动编码逻辑只运行一次</span></span><br><span class="line">               <span class="keyword">for</span> (String parameterName : parameterMap.keySet()) {</span><br><span class="line">                   String[] values = parameterMap.get(parameterName);</span><br><span class="line">                   <span class="keyword">if</span> (values != <span class="keyword">null</span>) {</span><br><span class="line">                       <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i &lt; values.length; i++) {</span><br><span class="line">                           <span class="keyword">try</span> {</span><br><span class="line">                               <span class="comment">// 处理get乱码</span></span><br><span class="line">                               values[i] = <span class="keyword">new</span> String(values[i]</span><br><span class="line">                                      .getBytes(<span class="string">"ISO-8859-1"</span>), <span class="string">"utf-8"</span>);</span><br><span class="line">                          } <span class="keyword">catch</span> (UnsupportedEncodingException e) {</span><br><span class="line">                               e.printStackTrace();</span><br><span class="line">                          }</span><br><span class="line">                      }</span><br><span class="line">                  }</span><br><span class="line">              }</span><br><span class="line">               hasEncode = <span class="keyword">true</span>;</span><br><span class="line">          }</span><br><span class="line">           <span class="keyword">return</span> parameterMap;</span><br><span class="line">      }</span><br><span class="line">       <span class="keyword">return</span> <span class="keyword">super</span>.getParameterMap();</span><br><span class="line">  }</span><br><span class="line"></span><br><span class="line">   <span class="comment">//取一个值</span></span><br><span class="line">   <span class="meta">@Override</span></span><br><span class="line">   <span class="function"><span class="keyword">public</span> String <span class="title">getParameter</span><span class="params">(String name)</span> </span>{</span><br><span class="line">       Map&lt;String, String[]&gt; parameterMap = getParameterMap();</span><br><span class="line">       String[] values = parameterMap.get(name);</span><br><span class="line">       <span class="keyword">if</span> (values == <span class="keyword">null</span>) {</span><br><span class="line">           <span class="keyword">return</span> <span class="keyword">null</span>;</span><br><span class="line">      }</span><br><span class="line">       <span class="keyword">return</span> values[<span class="number">0</span>]; <span class="comment">// 取回参数的第一个值</span></span><br><span class="line">  }</span><br><span class="line"></span><br><span class="line">   <span class="comment">//取所有值</span></span><br><span class="line">   <span class="meta">@Override</span></span><br><span class="line">   <span class="keyword">public</span> String[] getParameterValues(String name) {</span><br><span class="line">       Map&lt;String, String[]&gt; parameterMap = getParameterMap();</span><br><span class="line">       String[] values = parameterMap.get(name);</span><br><span class="line">       <span class="keyword">return</span> values;</span><br><span class="line">  }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><strong>然后在web.xml中配置这个过滤器即可！</strong></p><h2 id="5-整合SSM框架"><a href="#5-整合SSM框架" class="headerlink" title="5 整合SSM框架"></a>5 整合SSM框架</h2><blockquote><p>环境</p></blockquote><ul><li>IDEA 2020.2</li><li>MySQL 5.7.29</li><li>Tomcat 9</li><li>Maven 3.6</li></ul><blockquote><p>数据库环境</p></blockquote><p>创建一个数据库及表格</p><figure class="highlight sql"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">CREATE</span> DATABASE `ssmbuild`;</span><br><span class="line"></span><br><span class="line">USE `ssmbuild`;</span><br><span class="line"></span><br><span class="line"><span class="keyword">DROP</span> <span class="keyword">TABLE</span> IF <span class="keyword">EXISTS</span> `books`;</span><br><span class="line"></span><br><span class="line"><span class="keyword">CREATE</span> <span class="keyword">TABLE</span> `books` (</span><br><span class="line">`bookID` <span class="type">INT</span>(<span class="number">10</span>) <span class="keyword">NOT</span> <span class="keyword">NULL</span> AUTO_INCREMENT COMMENT <span class="string">'书id'</span>,</span><br><span class="line">`bookName` <span class="type">VARCHAR</span>(<span class="number">100</span>) <span class="keyword">NOT</span> <span class="keyword">NULL</span> COMMENT <span class="string">'书名'</span>,</span><br><span class="line">`bookCounts` <span class="type">INT</span>(<span class="number">11</span>) <span class="keyword">NOT</span> <span class="keyword">NULL</span> COMMENT <span class="string">'数量'</span>,</span><br><span class="line">`detail` <span class="type">VARCHAR</span>(<span class="number">200</span>) <span class="keyword">NOT</span> <span class="keyword">NULL</span> COMMENT <span class="string">'描述'</span>,</span><br><span class="line">KEY `bookID` (`bookID`)</span><br><span class="line">) ENGINE<span class="operator">=</span>INNODB <span class="keyword">DEFAULT</span> CHARSET<span class="operator">=</span>utf8</span><br><span class="line"></span><br><span class="line"><span class="keyword">INSERT</span>  <span class="keyword">INTO</span> `books`(`bookID`,`bookName`,`bookCounts`,`detail`)<span class="keyword">VALUES</span> </span><br><span class="line">(<span class="number">1</span>,<span class="string">'Java'</span>,<span class="number">1</span>,<span class="string">'从入门到放弃'</span>),</span><br><span class="line">(<span class="number">2</span>,<span class="string">'MySQL'</span>,<span class="number">10</span>,<span class="string">'从删库到跑路'</span>),</span><br><span class="line">(<span class="number">3</span>,<span class="string">'Linux'</span>,<span class="number">5</span>,<span class="string">'从进门到进牢'</span>);</span><br></pre></td></tr></tbody></table></figure><blockquote><p>项目环境搭建</p></blockquote><p>1、新建一个Maven项目！ssmbuild，添加web支持！</p><p>2、导入相关pom依赖以及Maven静态资源过滤问题解决！</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8"?&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">project</span> <span class="attr">xmlns</span>=<span class="string">"http://maven.apache.org/POM/4.0.0"</span></span></span><br><span class="line"><span class="tag">         <span class="attr">xmlns:xsi</span>=<span class="string">"http://www.w3.org/2001/XMLSchema-instance"</span></span></span><br><span class="line"><span class="tag">         <span class="attr">xsi:schemaLocation</span>=<span class="string">"http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">modelVersion</span>&gt;</span>4.0.0<span class="tag">&lt;/<span class="name">modelVersion</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>com.zzb<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>ssmbuild<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">version</span>&gt;</span>1.0-SNAPSHOT<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--导入依赖，需要Junit，数据库驱动，数据库连接池，servlet，jsp，el表达式，mybatis，mybatis-spring，spring，偷懒用的lombok--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">dependencies</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>junit<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>junit<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">version</span>&gt;</span>4.13<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br><span class="line"></span><br><span class="line">        <span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>mysql<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>mysql-connector-java<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">version</span>&gt;</span>5.1.48<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br><span class="line"></span><br><span class="line">        <span class="comment">&lt;!--数据库连接池--&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>com.mchange<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>c3p0<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">version</span>&gt;</span>0.9.5.2<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br><span class="line"></span><br><span class="line">        <span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>javax.servlet<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>servlet-api<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">version</span>&gt;</span>2.5<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>javax.servlet.jsp<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>jsp-api<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">version</span>&gt;</span>2.2<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>javax.servlet<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>jstl<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">version</span>&gt;</span>1.2<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br><span class="line"></span><br><span class="line">        <span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>org.mybatis<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>mybatis<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">version</span>&gt;</span>3.5.2<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>org.mybatis<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>mybatis-spring<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">version</span>&gt;</span>2.0.5<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br><span class="line"></span><br><span class="line">        <span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>org.springframework<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>spring-webmvc<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">version</span>&gt;</span>5.2.0.RELEASE<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br><span class="line"></span><br><span class="line">        <span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>org.springframework<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>spring-jdbc<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">version</span>&gt;</span>5.1.9.RELEASE<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">dependencies</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--静态资源过滤问题--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">build</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">resources</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">resource</span>&gt;</span></span><br><span class="line">                <span class="tag">&lt;<span class="name">directory</span>&gt;</span>src/main/java<span class="tag">&lt;/<span class="name">directory</span>&gt;</span></span><br><span class="line">                <span class="tag">&lt;<span class="name">includes</span>&gt;</span></span><br><span class="line">                    <span class="tag">&lt;<span class="name">include</span>&gt;</span>**/*.properties<span class="tag">&lt;/<span class="name">include</span>&gt;</span></span><br><span class="line">                    <span class="tag">&lt;<span class="name">include</span>&gt;</span>**/*.xml<span class="tag">&lt;/<span class="name">include</span>&gt;</span></span><br><span class="line">                <span class="tag">&lt;/<span class="name">includes</span>&gt;</span></span><br><span class="line">                <span class="tag">&lt;<span class="name">filtering</span>&gt;</span>true<span class="tag">&lt;/<span class="name">filtering</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;/<span class="name">resource</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">resource</span>&gt;</span></span><br><span class="line">                <span class="tag">&lt;<span class="name">directory</span>&gt;</span>src/main/resources<span class="tag">&lt;/<span class="name">directory</span>&gt;</span></span><br><span class="line">                <span class="tag">&lt;<span class="name">includes</span>&gt;</span></span><br><span class="line">                    <span class="tag">&lt;<span class="name">include</span>&gt;</span>**/*.properties<span class="tag">&lt;/<span class="name">include</span>&gt;</span></span><br><span class="line">                    <span class="tag">&lt;<span class="name">include</span>&gt;</span>**/*.xml<span class="tag">&lt;/<span class="name">include</span>&gt;</span></span><br><span class="line">                <span class="tag">&lt;/<span class="name">includes</span>&gt;</span></span><br><span class="line">                <span class="tag">&lt;<span class="name">filtering</span>&gt;</span>true<span class="tag">&lt;/<span class="name">filtering</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;/<span class="name">resource</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">resources</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">build</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">project</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>3、确定项目基本框架！</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201215165138707.png" alt="image-20201215165138707"></p><p>mybatis-config.xml</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8" ?&gt;</span></span><br><span class="line"><span class="meta">&lt;!DOCTYPE <span class="meta-keyword">configuration</span></span></span><br><span class="line"><span class="meta">        <span class="meta-keyword">PUBLIC</span> <span class="meta-string">"-//mybatis.org//DTD Config 3.0//EN"</span></span></span><br><span class="line"><span class="meta">        <span class="meta-string">"http://mybatis.org/dtd/mybatis-3-config.dtd"</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">configuration</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">configuration</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>applicationContext.xml</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8"?&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">beans</span> <span class="attr">xmlns</span>=<span class="string">"http://www.springframework.org/schema/beans"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xmlns:xsi</span>=<span class="string">"http://www.w3.org/2001/XMLSchema-instance"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xsi:schemaLocation</span>=<span class="string">"http://www.springframework.org/schema/beans</span></span></span><br><span class="line"><span class="tag"><span class="string">       http://www.springframework.org/schema/beans/spring-beans.xsd"</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">beans</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>database.properties</p><figure class="highlight properties"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">jdbc.driver</span>=<span class="string">com.mysql.jdbc.Driver</span></span><br><span class="line"><span class="meta">jdbc.url</span>=<span class="string">jdbc:mysql://localhost:3306/ssmbuild?useSSL=true&amp;verifyServerCertificate=false&amp;useUnicode=true&amp;characterEncoding=utf8</span></span><br><span class="line"><span class="meta">jdbc.username</span>=<span class="string">root</span></span><br><span class="line"><span class="meta">jdbc.password</span>=<span class="string">1234</span></span><br></pre></td></tr></tbody></table></figure><blockquote><p>MyBatis 层编写</p></blockquote><p>1、创建实体类Book</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.pojo;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Book</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">int</span> bookId;</span><br><span class="line">    <span class="keyword">private</span> String bookName;</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">int</span> bookCount;</span><br><span class="line">    <span class="keyword">private</span> String detail;</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="title">Book</span><span class="params">()</span> </span>{</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="title">Book</span><span class="params">(<span class="keyword">int</span> bookId, String bookName, <span class="keyword">int</span> bookCount, String detail)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.bookId = bookId;</span><br><span class="line">        <span class="keyword">this</span>.bookName = bookName;</span><br><span class="line">        <span class="keyword">this</span>.bookCount = bookCount;</span><br><span class="line">        <span class="keyword">this</span>.detail = detail;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">getBookId</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> bookId;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setBookId</span><span class="params">(<span class="keyword">int</span> bookId)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.bookId = bookId;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">getBookName</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> bookName;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setBookName</span><span class="params">(String bookName)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.bookName = bookName;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">getBookCount</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> bookCount;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setBookCount</span><span class="params">(<span class="keyword">int</span> bookCount)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.bookCount = bookCount;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">getDetail</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> detail;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setDetail</span><span class="params">(String detail)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.detail = detail;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">toString</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> <span class="string">"Book{"</span> +</span><br><span class="line">                <span class="string">"bookId="</span> + bookId +</span><br><span class="line">                <span class="string">", bookName='"</span> + bookName + <span class="string">'\''</span> +</span><br><span class="line">                <span class="string">", bookCount="</span> + bookCount +</span><br><span class="line">                <span class="string">", detail='"</span> + detail + <span class="string">'\''</span> +</span><br><span class="line">                <span class="string">'}'</span>;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>2、编写Mapper层Mapper接口</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.mapper;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> com.zzb.pojo.Book;</span><br><span class="line"><span class="keyword">import</span> org.apache.ibatis.annotations.Param;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> java.util.List;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">BookMapper</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 增加一本书</span></span><br><span class="line">    <span class="function"><span class="keyword">int</span> <span class="title">addBook</span><span class="params">(Book book)</span></span>;</span><br><span class="line">    <span class="comment">// 删除一本书</span></span><br><span class="line">    <span class="function"><span class="keyword">int</span> <span class="title">deleteBookById</span><span class="params">(<span class="meta">@Param("bookId")</span> <span class="keyword">int</span> id)</span></span>;</span><br><span class="line">    <span class="comment">// 更新一本书</span></span><br><span class="line">    <span class="function"><span class="keyword">int</span> <span class="title">updateBook</span><span class="params">(Book book)</span></span>;</span><br><span class="line">    <span class="comment">// 查询一本书</span></span><br><span class="line">    <span class="function">Book <span class="title">queryBookById</span><span class="params">(<span class="meta">@Param("bookId")</span> <span class="keyword">int</span> id)</span></span>;</span><br><span class="line">    <span class="comment">// 查询所有书</span></span><br><span class="line">    <span class="function">List&lt;Book&gt; <span class="title">queryAllBook</span><span class="params">()</span></span>;</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>3、编写对应的Mapper.xml配置文件</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8" ?&gt;</span></span><br><span class="line"><span class="meta">&lt;!DOCTYPE <span class="meta-keyword">mapper</span></span></span><br><span class="line"><span class="meta">        <span class="meta-keyword">PUBLIC</span> <span class="meta-string">"-//mybatis.org//DTD Config 3.0//EN"</span></span></span><br><span class="line"><span class="meta">        <span class="meta-string">"http://mybatis.org/dtd/mybatis-3-mapper.dtd"</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">mapper</span> <span class="attr">namespace</span>=<span class="string">"com.zzb.mapper.BookMapper"</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">insert</span> <span class="attr">id</span>=<span class="string">"addBook"</span> <span class="attr">parameterType</span>=<span class="string">"Book"</span>&gt;</span></span><br><span class="line">        INSERT INTO books(bookName, bookCount, detail) VALUES (#{bookName}, #{bookCount}, #{detail})</span><br><span class="line">    <span class="tag">&lt;/<span class="name">insert</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">delete</span> <span class="attr">id</span>=<span class="string">"deleteBookById"</span> <span class="attr">parameterType</span>=<span class="string">"int"</span>&gt;</span></span><br><span class="line">        DELETE FROM books WHERE bookId = #{bookId}</span><br><span class="line">    <span class="tag">&lt;/<span class="name">delete</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">update</span> <span class="attr">id</span>=<span class="string">"updateBook"</span> <span class="attr">parameterType</span>=<span class="string">"Book"</span>&gt;</span></span><br><span class="line">        UPDATE books SET bookName = #{bookName}, bookCount = #{bookCount}, detail = #{detail} WHERE bookId = #{bookId}</span><br><span class="line">    <span class="tag">&lt;/<span class="name">update</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"queryBookById"</span> <span class="attr">parameterType</span>=<span class="string">"int"</span>&gt;</span></span><br><span class="line">        SELECT * FROM book WHERE bookId = #{bookId}</span><br><span class="line">    <span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"queryAllBook"</span> <span class="attr">resultType</span>=<span class="string">"Book"</span>&gt;</span></span><br><span class="line">        SELECT * FROM book</span><br><span class="line">    <span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">mapper</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>4、编写Service层的接口和实现类</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.service;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> com.zzb.pojo.Book;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> java.util.List;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">BookService</span> </span>{</span><br><span class="line">    <span class="comment">// 增加一本书</span></span><br><span class="line">    <span class="function"><span class="keyword">int</span> <span class="title">addBook</span><span class="params">(Book book)</span></span>;</span><br><span class="line">    <span class="comment">// 删除一本书</span></span><br><span class="line">    <span class="function"><span class="keyword">int</span> <span class="title">deleteBookById</span><span class="params">(<span class="keyword">int</span> id)</span></span>;</span><br><span class="line">    <span class="comment">// 更新一本书</span></span><br><span class="line">    <span class="function"><span class="keyword">int</span> <span class="title">updateBook</span><span class="params">(Book book)</span></span>;</span><br><span class="line">    <span class="comment">// 查询一本书</span></span><br><span class="line">    <span class="function">Book <span class="title">queryBookById</span><span class="params">(<span class="keyword">int</span> id)</span></span>;</span><br><span class="line">    <span class="comment">// 查询所有书</span></span><br><span class="line">    <span class="function">List&lt;Book&gt; <span class="title">queryAllBook</span><span class="params">()</span></span>;</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.service;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> com.zzb.mapper.BookMapper;</span><br><span class="line"><span class="keyword">import</span> com.zzb.pojo.Book;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> java.util.List;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">BookServiceImpl</span> <span class="keyword">implements</span> <span class="title">BookService</span></span>{</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 组合Mapper层</span></span><br><span class="line">    <span class="keyword">private</span> BookMapper bookMapper;</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setBookMapper</span><span class="params">(BookMapper bookMapper)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.bookMapper = bookMapper;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">addBook</span><span class="params">(Book book)</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> bookMapper.addBook(book);</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">deleteBookById</span><span class="params">(<span class="keyword">int</span> id)</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> bookMapper.deleteBookById(id);</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">updateBook</span><span class="params">(Book book)</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> bookMapper.updateBook(book);</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> Book <span class="title">queryBookById</span><span class="params">(<span class="keyword">int</span> id)</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> bookMapper.queryBookById(id);</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> List&lt;Book&gt; <span class="title">queryAllBook</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> bookMapper.queryAllBook();</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>5、配置MyBatis核心配置文件</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8" ?&gt;</span></span><br><span class="line"><span class="meta">&lt;!DOCTYPE <span class="meta-keyword">configuration</span></span></span><br><span class="line"><span class="meta">        <span class="meta-keyword">PUBLIC</span> <span class="meta-string">"-//mybatis.org//DTD Config 3.0//EN"</span></span></span><br><span class="line"><span class="meta">        <span class="meta-string">"http://mybatis.org/dtd/mybatis-3-config.dtd"</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">configuration</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--给实体类起别名--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">typeAliases</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">package</span> <span class="attr">name</span>=<span class="string">"com.zzb.pojo"</span>/&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">typeAliases</span>&gt;</span></span><br><span class="line">    <span class="comment">&lt;!--注册Mapper--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">mappers</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">mapper</span> <span class="attr">class</span>=<span class="string">"com.zzb.mapper.BookMapper"</span>/&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">mappers</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">configuration</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><blockquote><p>Spring 层编写</p></blockquote><p>1、Spring 整合 MyBatis层，spring-dao.xml</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8"?&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">beans</span> <span class="attr">xmlns</span>=<span class="string">"http://www.springframework.org/schema/beans"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xmlns:xsi</span>=<span class="string">"http://www.w3.org/2001/XMLSchema-instance"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xmlns:context</span>=<span class="string">"http://www.springframework.org/schema/context"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xsi:schemaLocation</span>=<span class="string">"http://www.springframework.org/schema/beans</span></span></span><br><span class="line"><span class="tag"><span class="string">       http://www.springframework.org/schema/beans/spring-beans.xsd</span></span></span><br><span class="line"><span class="tag"><span class="string">       http://www.springframework.org/schema/context</span></span></span><br><span class="line"><span class="tag"><span class="string">       https://www.springframework.org/schema/context/spring-context.xsd"</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--1、关联数据库配置文件--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">context:property-placeholder</span> <span class="attr">location</span>=<span class="string">"classpath:database.properties"</span>/&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--2、数据库连接池--&gt;</span></span><br><span class="line">    <span class="comment">&lt;!--数据库连接池</span></span><br><span class="line"><span class="comment">        dbcp 半自动化操作 不能自动连接</span></span><br><span class="line"><span class="comment">        c3p0 自动化操作（自动的加载配置文件 并且设置到对象里面）</span></span><br><span class="line"><span class="comment">    --&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">bean</span> <span class="attr">id</span>=<span class="string">"dataSource"</span> <span class="attr">class</span>=<span class="string">"com.mchange.v2.c3p0.ComboPooledDataSource"</span>&gt;</span></span><br><span class="line">        <span class="comment">&lt;!-- 配置连接池属性 --&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"driverClass"</span> <span class="attr">value</span>=<span class="string">"${jdbc.driver}"</span>/&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"jdbcUrl"</span> <span class="attr">value</span>=<span class="string">"${jdbc.url}"</span>/&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"user"</span> <span class="attr">value</span>=<span class="string">"${jdbc.username}"</span>/&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"password"</span> <span class="attr">value</span>=<span class="string">"${jdbc.password}"</span>/&gt;</span></span><br><span class="line"></span><br><span class="line">        <span class="comment">&lt;!-- c3p0连接池的私有属性 --&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"maxPoolSize"</span> <span class="attr">value</span>=<span class="string">"30"</span>/&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"minPoolSize"</span> <span class="attr">value</span>=<span class="string">"10"</span>/&gt;</span></span><br><span class="line">        <span class="comment">&lt;!-- 关闭连接后不自动commit --&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"autoCommitOnClose"</span> <span class="attr">value</span>=<span class="string">"false"</span>/&gt;</span></span><br><span class="line">        <span class="comment">&lt;!-- 获取连接超时时间 --&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"checkoutTimeout"</span> <span class="attr">value</span>=<span class="string">"10000"</span>/&gt;</span></span><br><span class="line">        <span class="comment">&lt;!-- 当获取连接失败重试次数 --&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"acquireRetryAttempts"</span> <span class="attr">value</span>=<span class="string">"2"</span>/&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">bean</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--3、SqlSessionFactory--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">bean</span> <span class="attr">id</span>=<span class="string">"sqlSessionFactory"</span> <span class="attr">class</span>=<span class="string">"org.mybatis.spring.SqlSessionFactoryBean"</span>&gt;</span></span><br><span class="line">        <span class="comment">&lt;!--注入数据库连接池--&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"dataSource"</span> <span class="attr">ref</span>=<span class="string">"dataSource"</span>/&gt;</span></span><br><span class="line">        <span class="comment">&lt;!--配置MyBatis核心配置文件--&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"configLocation"</span> <span class="attr">value</span>=<span class="string">"classpath:mybatis-config.xml"</span>/&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">bean</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--4、配置扫描Dao接口包，动态实现Dao接口注入到spring容器中--&gt;</span></span><br><span class="line">    <span class="comment">&lt;!--解释 ：https://www.cnblogs.com/jpfss/p/7799806.html--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">bean</span> <span class="attr">class</span>=<span class="string">"org.mybatis.spring.mapper.MapperScannerConfigurer"</span>&gt;</span></span><br><span class="line">        <span class="comment">&lt;!--注入SqlSessionFactory--&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"sqlSessionFactoryBeanName"</span> <span class="attr">value</span>=<span class="string">"sqlSessionFactory"</span>/&gt;</span></span><br><span class="line">        <span class="comment">&lt;!--配置需要扫描的包--&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"basePackage"</span> <span class="attr">value</span>=<span class="string">"com.zzb.mapper"</span>/&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">bean</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">beans</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>2、Spring 整合 Service 层，spring-service.xml</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8"?&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">beans</span> <span class="attr">xmlns</span>=<span class="string">"http://www.springframework.org/schema/beans"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xmlns:xsi</span>=<span class="string">"http://www.w3.org/2001/XMLSchema-instance"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xmlns:context</span>=<span class="string">"http://www.springframework.org/schema/context"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xsi:schemaLocation</span>=<span class="string">"http://www.springframework.org/schema/beans</span></span></span><br><span class="line"><span class="tag"><span class="string">       http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd"</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--1、扫描service层下面相关的包--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">context:component-scan</span> <span class="attr">base-package</span>=<span class="string">"com.zzb.service"</span>/&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--2、将业务层实现类注入到Spring中--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">bean</span> <span class="attr">id</span>=<span class="string">"bookServiceImpl"</span> <span class="attr">class</span>=<span class="string">"com.zzb.service.BookServiceImpl"</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"bookMapper"</span> <span class="attr">ref</span>=<span class="string">"bookMapper"</span>/&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">bean</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--3、配置事务管理器--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">bean</span> <span class="attr">id</span>=<span class="string">"transactionManager"</span> <span class="attr">class</span>=<span class="string">"org.springframework.jdbc.datasource.DataSourceTransactionManager"</span>&gt;</span></span><br><span class="line">        <span class="comment">&lt;!--注入数据库连接池--&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"dataSource"</span> <span class="attr">ref</span>=<span class="string">"dataSource"</span>/&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">bean</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--4、AOP织入事务管理--&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">beans</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><blockquote><p>Spring MVC 层</p></blockquote><p>1、spring-mvc.xml</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8"?&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">beans</span> <span class="attr">xmlns</span>=<span class="string">"http://www.springframework.org/schema/beans"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xmlns:xsi</span>=<span class="string">"http://www.w3.org/2001/XMLSchema-instance"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xmlns:context</span>=<span class="string">"http://www.springframework.org/schema/context"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xmlns:mvc</span>=<span class="string">"http://www.springframework.org/schema/mvc"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xsi:schemaLocation</span>=<span class="string">"http://www.springframework.org/schema/beans</span></span></span><br><span class="line"><span class="tag"><span class="string">       http://www.springframework.org/schema/beans/spring-beans.xsd</span></span></span><br><span class="line"><span class="tag"><span class="string">       http://www.springframework.org/schema/context</span></span></span><br><span class="line"><span class="tag"><span class="string">       https://www.springframework.org/schema/context/spring-context.xsd</span></span></span><br><span class="line"><span class="tag"><span class="string">       http://www.springframework.org/schema/mvc</span></span></span><br><span class="line"><span class="tag"><span class="string">       https://www.springframework.org/schema/mvc/spring-mvc.xsd"</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--自动扫描包，让指定包下的注解生效，由IOC容器统一管理--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">context:component-scan</span> <span class="attr">base-package</span>=<span class="string">"com.zzb.controller"</span>/&gt;</span></span><br><span class="line">    <span class="comment">&lt;!--让Spring MVC不处理静态资源，例如.mp3 .css .jpg等不走视图解析器--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">mvc:default-servlet-handler</span>/&gt;</span></span><br><span class="line">    <span class="comment">&lt;!--</span></span><br><span class="line"><span class="comment">       支持mvc注解驱动</span></span><br><span class="line"><span class="comment">       在spring中一般采用@RequestMapping注解来完成映射关系</span></span><br><span class="line"><span class="comment">       要想使@RequestMapping注解生效</span></span><br><span class="line"><span class="comment">       必须向上下文中注册DefaultAnnotationHandlerMapping</span></span><br><span class="line"><span class="comment">       和一个AnnotationMethodHandlerAdapter实例</span></span><br><span class="line"><span class="comment">       这两个实例分别在类级别和方法级别处理。</span></span><br><span class="line"><span class="comment">       而annotation-driven配置帮助我们自动完成上述两个实例的注入</span></span><br><span class="line"><span class="comment">    --&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">mvc:annotation-driven</span>/&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--视图解析器--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">bean</span> <span class="attr">class</span>=<span class="string">"org.springframework.web.servlet.view.InternalResourceViewResolver"</span> <span class="attr">id</span>=<span class="string">"InternalResourceViewResolver"</span>&gt;</span></span><br><span class="line">        <span class="comment">&lt;!--前缀--&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"prefix"</span> <span class="attr">value</span>=<span class="string">"/WEB-INF/jsp/"</span>/&gt;</span></span><br><span class="line">        <span class="comment">&lt;!--后缀--&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"suffix"</span> <span class="attr">value</span>=<span class="string">".jsp"</span>/&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">bean</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">beans</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>2、Spring 配置文件整合，applicationContext.xml</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8"?&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">beans</span> <span class="attr">xmlns</span>=<span class="string">"http://www.springframework.org/schema/beans"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xmlns:xsi</span>=<span class="string">"http://www.w3.org/2001/XMLSchema-instance"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xsi:schemaLocation</span>=<span class="string">"http://www.springframework.org/schema/beans</span></span></span><br><span class="line"><span class="tag"><span class="string">       http://www.springframework.org/schema/beans/spring-beans.xsd"</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">import</span> <span class="attr">resource</span>=<span class="string">"spring-dao.xml"</span>/&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">import</span> <span class="attr">resource</span>=<span class="string">"spring-service.xml"</span>/&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">import</span> <span class="attr">resource</span>=<span class="string">"spring-mvc.xml"</span>/&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">beans</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>3、web.xml</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8"?&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">web-app</span> <span class="attr">xmlns</span>=<span class="string">"http://xmlns.jcp.org/xml/ns/javaee"</span></span></span><br><span class="line"><span class="tag">         <span class="attr">xmlns:xsi</span>=<span class="string">"http://www.w3.org/2001/XMLSchema-instance"</span></span></span><br><span class="line"><span class="tag">         <span class="attr">xsi:schemaLocation</span>=<span class="string">"http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"</span></span></span><br><span class="line"><span class="tag">         <span class="attr">version</span>=<span class="string">"4.0"</span>&gt;</span></span><br><span class="line">    </span><br><span class="line">    <span class="comment">&lt;!--注册dispatcherServlet--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">servlet</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">servlet-name</span>&gt;</span>dispatcherServlet<span class="tag">&lt;/<span class="name">servlet-name</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">servlet-class</span>&gt;</span>org.springframework.web.servlet.DispatcherServlet<span class="tag">&lt;/<span class="name">servlet-class</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">init-param</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">param-name</span>&gt;</span>contextConfigLocation<span class="tag">&lt;/<span class="name">param-name</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">param-value</span>&gt;</span>classpath:applicationContext.xml<span class="tag">&lt;/<span class="name">param-value</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">init-param</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">load-on-startup</span>&gt;</span>1<span class="tag">&lt;/<span class="name">load-on-startup</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">servlet</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">servlet-mapping</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">servlet-name</span>&gt;</span>dispatcherServlet<span class="tag">&lt;/<span class="name">servlet-name</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">url-pattern</span>&gt;</span>/<span class="tag">&lt;/<span class="name">url-pattern</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">servlet-mapping</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--配置编码过滤器--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">filter</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">filter-name</span>&gt;</span>encodingFilter<span class="tag">&lt;/<span class="name">filter-name</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">filter-class</span>&gt;</span>org.springframework.web.filter.CharacterEncodingFilter<span class="tag">&lt;/<span class="name">filter-class</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">init-param</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">param-name</span>&gt;</span>encoding<span class="tag">&lt;/<span class="name">param-name</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">param-value</span>&gt;</span>utf-8<span class="tag">&lt;/<span class="name">param-value</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">init-param</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">filter</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">filter-mapping</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">filter-name</span>&gt;</span>encodingFilter<span class="tag">&lt;/<span class="name">filter-name</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">url-pattern</span>&gt;</span>/*<span class="tag">&lt;/<span class="name">url-pattern</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">filter-mapping</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--Session过期时间--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">session-config</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">session-timeout</span>&gt;</span>15<span class="tag">&lt;/<span class="name">session-timeout</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">session-config</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">web-app</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p><strong>Controller 和视图层编写</strong></p><p>1、查询全部书籍， BookController 类编写</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.controller;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> com.zzb.pojo.Book;</span><br><span class="line"><span class="keyword">import</span> com.zzb.service.BookService;</span><br><span class="line"><span class="keyword">import</span> org.springframework.beans.factory.annotation.Autowired;</span><br><span class="line"><span class="keyword">import</span> org.springframework.beans.factory.annotation.Qualifier;</span><br><span class="line"><span class="keyword">import</span> org.springframework.stereotype.Controller;</span><br><span class="line"><span class="keyword">import</span> org.springframework.ui.Model;</span><br><span class="line"><span class="keyword">import</span> org.springframework.web.bind.annotation.RequestMapping;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> java.util.List;</span><br><span class="line"></span><br><span class="line"><span class="meta">@Controller</span></span><br><span class="line"><span class="meta">@RequestMapping("/book")</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">BookController</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="comment">// controller层调用业务层</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">// 自动装备指定参数</span></span><br><span class="line">    <span class="meta">@Autowired</span></span><br><span class="line">    <span class="meta">@Qualifier("bookServiceImpl")</span></span><br><span class="line">    <span class="keyword">private</span> BookService bookService;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@RequestMapping("/allBook")</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">allBook</span><span class="params">(Model model)</span></span>{</span><br><span class="line">        List&lt;Book&gt; bookList = bookService.queryAllBook();</span><br><span class="line"></span><br><span class="line">        model.addAttribute(<span class="string">"bookList"</span>, bookList);</span><br><span class="line"></span><br><span class="line">        <span class="keyword">return</span> <span class="string">"allBook"</span>;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>2、编写首页 index.jsp</p><figure class="highlight"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br></pre></td><td class="code"><pre><span class="line">&lt;%@ page contentType=<span class="string">"text/html;charset=UTF-8"</span> language=<span class="string">"java"</span> %&gt;</span><br><span class="line">&lt;html&gt;</span><br><span class="line">  &lt;head&gt;</span><br><span class="line">    &lt;title&gt;$Title$&lt;/title&gt;</span><br><span class="line">    &lt;style type=<span class="string">"text/css"</span>&gt;</span><br><span class="line">      a {</span><br><span class="line">        text-decoration: none;</span><br><span class="line">        color: black;</span><br><span class="line">        font-size: 18px;</span><br><span class="line">      }</span><br><span class="line">      h3 {</span><br><span class="line">        width: 180px;</span><br><span class="line">        height: 38px;</span><br><span class="line">        margin: 100px auto;</span><br><span class="line">        text-align: center;</span><br><span class="line">        line-height: 38px;</span><br><span class="line">        background: deepskyblue;</span><br><span class="line">        border-radius: 4px;</span><br><span class="line">      }</span><br><span class="line">    &lt;/style&gt;</span><br><span class="line">  &lt;/head&gt;</span><br><span class="line">  &lt;body&gt;</span><br><span class="line">  &lt;h3&gt;</span><br><span class="line">    &lt;a href="${pageContext.request.contextPath}/book/allBook"&gt;进入书籍展示页面&lt;/a&gt;</span><br><span class="line">  &lt;/h3&gt;</span><br><span class="line">  &lt;/body&gt;</span><br><span class="line">&lt;/html&gt;</span><br></pre></td></tr></tbody></table></figure><p>3、数据列表页面 allBook.jsp</p><figure class="highlight"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br></pre></td><td class="code"><pre><span class="line">&lt;%@ taglib prefix=<span class="string">"c"</span> uri=<span class="string">"http://java.sun.com/jsp/jstl/core"</span> %&gt;</span><br><span class="line">&lt;%@ page contentType=<span class="string">"text/html;charset=UTF-8"</span> language=<span class="string">"java"</span> %&gt;</span><br><span class="line">&lt;html&gt;</span><br><span class="line">&lt;head&gt;</span><br><span class="line">    &lt;title&gt;书籍列表&lt;/title&gt;</span><br><span class="line">    &lt;meta name=<span class="string">"viewport"</span> content=<span class="string">"width=device-width, initial-scale=1.0"</span>&gt;</span><br><span class="line">    &lt;!-- 引入 Bootstrap --&gt;</span><br><span class="line">    &lt;link href=<span class="string">"https://cdn.bootcss.com/bootstrap/3.3.7/css/bootstrap.min.css"</span> rel=<span class="string">"stylesheet"</span>&gt;</span><br><span class="line">&lt;/head&gt;</span><br><span class="line">&lt;body&gt;</span><br><span class="line"></span><br><span class="line">&lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">"container"</span>&gt;</span><br><span class="line"></span><br><span class="line">    &lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">"row clearfix"</span>&gt;</span><br><span class="line">        &lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">"col-md-12 column"</span>&gt;</span><br><span class="line">            &lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">"page-header"</span>&gt;</span><br><span class="line">                &lt;h1&gt;</span><br><span class="line">                    &lt;small&gt;书籍列表 —— 显示所有书籍&lt;/small&gt;</span><br><span class="line">                &lt;/h1&gt;</span><br><span class="line">            &lt;/div&gt;</span><br><span class="line">        &lt;/div&gt;</span><br><span class="line">    &lt;/div&gt;</span><br><span class="line"></span><br><span class="line">    &lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">"row"</span>&gt;</span><br><span class="line">        &lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">"col-md-4 column"</span>&gt;</span><br><span class="line">            &lt;a class="btn btn-primary" href="${pageContext.request.contextPath}/book/toAddBook"&gt;新增&lt;/a&gt;</span><br><span class="line">        &lt;/div&gt;</span><br><span class="line">    &lt;/div&gt;</span><br><span class="line"></span><br><span class="line">    &lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">"row clearfix"</span>&gt;</span><br><span class="line">        &lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">"col-md-12 column"</span>&gt;</span><br><span class="line">            &lt;table <span class="class"><span class="keyword">class</span></span>=<span class="string">"table table-hover table-striped"</span>&gt;</span><br><span class="line">                &lt;thead&gt;</span><br><span class="line">                &lt;tr&gt;</span><br><span class="line">                    &lt;th&gt;书籍编号&lt;/th&gt;</span><br><span class="line">                    &lt;th&gt;书籍名字&lt;/th&gt;</span><br><span class="line">                    &lt;th&gt;书籍数量&lt;/th&gt;</span><br><span class="line">                    &lt;th&gt;书籍详情&lt;/th&gt;</span><br><span class="line">                    &lt;th&gt;操作&lt;/th&gt;</span><br><span class="line">                &lt;/tr&gt;</span><br><span class="line">                &lt;/thead&gt;</span><br><span class="line"></span><br><span class="line">                &lt;tbody&gt;</span><br><span class="line">                &lt;c:forEach <span class="keyword">var</span>=<span class="string">"book"</span> items=<span class="string">"${requestScope.get('bookList')}"</span>&gt;</span><br><span class="line"></span><br><span class="line">                    &lt;tr&gt;</span><br><span class="line">                        &lt;td&gt;${book.getBookId()}&lt;/td&gt;</span><br><span class="line">                        &lt;td&gt;${book.getBookName()}&lt;/td&gt;</span><br><span class="line">                        &lt;td&gt;${book.getBookCount()}&lt;/td&gt;</span><br><span class="line">                        &lt;td&gt;${book.getDetail()}&lt;/td&gt;</span><br><span class="line">                        &lt;td&gt;</span><br><span class="line">                            &lt;a href="${pageContext.request.contextPath}/book/toUpdateBook?id=${book.getBookId()}"&gt;更改&lt;/a&gt;</span><br><span class="line">                            |</span><br><span class="line">                            &lt;a href="${pageContext.request.contextPath}/book/del/${book.getBookId()}"&gt;删除&lt;/a&gt;</span><br><span class="line">                        &lt;/td&gt;</span><br><span class="line">                    &lt;/tr&gt;</span><br><span class="line">                &lt;/c:forEach&gt;</span><br><span class="line">                &lt;/tbody&gt;</span><br><span class="line">            &lt;/table&gt;</span><br><span class="line">        &lt;/div&gt;</span><br><span class="line">    &lt;/div&gt;</span><br><span class="line">&lt;/div&gt;</span><br><span class="line">&lt;/body&gt;</span><br><span class="line">&lt;/html&gt;</span><br></pre></td></tr></tbody></table></figure><p>4、添加书籍，BookController类编写</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 添加书籍功能</span></span><br><span class="line"><span class="comment">// 首先跳转到添加书籍页面</span></span><br><span class="line"><span class="meta">@RequestMapping("toAddBook")</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> String <span class="title">toAddBook</span><span class="params">()</span></span>{</span><br><span class="line">    <span class="keyword">return</span> <span class="string">"addBook"</span>;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">// 执行数据添加</span></span><br><span class="line"><span class="meta">@RequestMapping("addBook")</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> String <span class="title">addBook</span><span class="params">(Book book)</span></span>{</span><br><span class="line"></span><br><span class="line">    <span class="keyword">int</span> i = bookService.addBook(book);</span><br><span class="line">    <span class="keyword">if</span>(i == <span class="number">1</span>){</span><br><span class="line">        System.out.println(<span class="string">"书籍添加成果！"</span>);</span><br><span class="line">    }<span class="keyword">else</span>{</span><br><span class="line">        System.out.println(<span class="string">"书籍添加失败！"</span>);</span><br><span class="line">    }</span><br><span class="line">    <span class="keyword">return</span> <span class="string">"redirect:/book/allBook"</span>;</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>5、添加书籍jsp页面</p><figure class="highlight"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br></pre></td><td class="code"><pre><span class="line">&lt;%@ taglib prefix=<span class="string">"c"</span> uri=<span class="string">"http://java.sun.com/jsp/jstl/core"</span> %&gt;</span><br><span class="line">&lt;%@ page contentType=<span class="string">"text/html;charset=UTF-8"</span> language=<span class="string">"java"</span> %&gt;</span><br><span class="line">&lt;html&gt;</span><br><span class="line">&lt;head&gt;</span><br><span class="line">    &lt;title&gt;新增书籍&lt;/title&gt;</span><br><span class="line">    &lt;meta name=<span class="string">"viewport"</span> content=<span class="string">"width=device-width, initial-scale=1.0"</span>&gt;</span><br><span class="line">    &lt;!-- 引入 Bootstrap --&gt;</span><br><span class="line">    &lt;link href=<span class="string">"https://cdn.bootcss.com/bootstrap/3.3.7/css/bootstrap.min.css"</span> rel=<span class="string">"stylesheet"</span>&gt;</span><br><span class="line">&lt;/head&gt;</span><br><span class="line">&lt;body&gt;</span><br><span class="line"></span><br><span class="line">&lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">"container"</span>&gt;</span><br><span class="line"></span><br><span class="line">    &lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">"row clearfix"</span>&gt;</span><br><span class="line">        &lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">"col-md-12 column"</span>&gt;</span><br><span class="line">            &lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">"page-header"</span>&gt;</span><br><span class="line">                &lt;h1&gt;</span><br><span class="line">                    &lt;small&gt;新增书籍&lt;/small&gt;</span><br><span class="line">                &lt;/h1&gt;</span><br><span class="line">            &lt;/div&gt;</span><br><span class="line">        &lt;/div&gt;</span><br><span class="line">    &lt;/div&gt;</span><br><span class="line">    &lt;form action=<span class="string">"${pageContext.request.contextPath}/book/addBook"</span> method=<span class="string">"post"</span>&gt;</span><br><span class="line">        书籍名称：&lt;input type=<span class="string">"text"</span> name=<span class="string">"bookName"</span>&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;</span><br><span class="line">        书籍数量：&lt;input type=<span class="string">"text"</span> name=<span class="string">"bookCount"</span>&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;</span><br><span class="line">        书籍详情：&lt;input type=<span class="string">"text"</span> name=<span class="string">"detail"</span>&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;</span><br><span class="line">        &lt;input type=<span class="string">"submit"</span> value=<span class="string">"添加"</span>&gt;</span><br><span class="line">    &lt;/form&gt;</span><br><span class="line"></span><br><span class="line">&lt;/div&gt;</span><br><span class="line">&lt;/body&gt;</span><br><span class="line">&lt;/html&gt;</span><br></pre></td></tr></tbody></table></figure><p>6、修改书籍，BookController类编写</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 修改书籍信息</span></span><br><span class="line"><span class="comment">// 跳转到书籍信息修改页面</span></span><br><span class="line"><span class="meta">@RequestMapping("toUpdateBook")</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> String <span class="title">toUpdateBook</span><span class="params">(<span class="meta">@RequestParam("id")</span> <span class="keyword">int</span> bookId, Model model)</span></span>{</span><br><span class="line">    <span class="comment">// 首先查询到书籍的原信息，在页面中进行展示</span></span><br><span class="line">    Book book = bookService.queryBookById(bookId);</span><br><span class="line">    System.out.println(book.toString());</span><br><span class="line">    model.addAttribute(<span class="string">"book"</span>, book);</span><br><span class="line">    <span class="keyword">return</span> <span class="string">"updateBook"</span>;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">// 执行修改数据操作</span></span><br><span class="line"><span class="meta">@RequestMapping("updateBook")</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> String <span class="title">updateBook</span><span class="params">(Book book)</span></span>{</span><br><span class="line">    <span class="keyword">int</span> i = bookService.updateBook(book);</span><br><span class="line">    <span class="keyword">if</span>(i == <span class="number">1</span>){</span><br><span class="line">        System.out.println(<span class="string">"修改书籍成功！"</span>);</span><br><span class="line">    }<span class="keyword">else</span>{</span><br><span class="line">        System.out.println(<span class="string">"修改书籍失败！"</span>);</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> <span class="string">"redirect:/book/allBook"</span>;</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>7、修改书籍jsp页面</p><figure class="highlight"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br></pre></td><td class="code"><pre><span class="line">&lt;%@ taglib prefix=<span class="string">"c"</span> uri=<span class="string">"http://java.sun.com/jsp/jstl/core"</span> %&gt;</span><br><span class="line">&lt;%@ page contentType=<span class="string">"text/html;charset=UTF-8"</span> language=<span class="string">"java"</span> %&gt;</span><br><span class="line">&lt;html&gt;</span><br><span class="line">&lt;head&gt;</span><br><span class="line">    &lt;title&gt;新增书籍&lt;/title&gt;</span><br><span class="line">    &lt;meta name=<span class="string">"viewport"</span> content=<span class="string">"width=device-width, initial-scale=1.0"</span>&gt;</span><br><span class="line">    &lt;!-- 引入 Bootstrap --&gt;</span><br><span class="line">    &lt;link href=<span class="string">"https://cdn.bootcss.com/bootstrap/3.3.7/css/bootstrap.min.css"</span> rel=<span class="string">"stylesheet"</span>&gt;</span><br><span class="line">&lt;/head&gt;</span><br><span class="line">&lt;body&gt;</span><br><span class="line"></span><br><span class="line">&lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">"container"</span>&gt;</span><br><span class="line"></span><br><span class="line">    &lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">"row clearfix"</span>&gt;</span><br><span class="line">        &lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">"col-md-12 column"</span>&gt;</span><br><span class="line">            &lt;div <span class="class"><span class="keyword">class</span></span>=<span class="string">"page-header"</span>&gt;</span><br><span class="line">                &lt;h1&gt;</span><br><span class="line">                    &lt;small&gt;修改书籍书籍&lt;/small&gt;</span><br><span class="line">                &lt;/h1&gt;</span><br><span class="line">            &lt;/div&gt;</span><br><span class="line">        &lt;/div&gt;</span><br><span class="line">    &lt;/div&gt;</span><br><span class="line">    &lt;form action=<span class="string">"${pageContext.request.contextPath}/book/updateBook"</span> method=<span class="string">"post"</span>&gt;</span><br><span class="line">        &lt;%--隐藏域传递书籍id--%&gt;</span><br><span class="line">        &lt;input type=<span class="string">"hidden"</span> name=<span class="string">"bookId"</span> value=<span class="string">"${book.getBookId()}"</span>&gt;</span><br><span class="line">        书籍名称：&lt;input type=<span class="string">"text"</span> name=<span class="string">"bookName"</span> value=<span class="string">"${book.getBookName()}"</span>&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;</span><br><span class="line">        书籍数量：&lt;input type=<span class="string">"text"</span> name=<span class="string">"bookCount"</span> value=<span class="string">"${book.getBookCount()}"</span>&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;</span><br><span class="line">        书籍详情：&lt;input type=<span class="string">"text"</span> name=<span class="string">"detail"</span> value=<span class="string">"${book.getDetail()}"</span>&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;</span><br><span class="line">        &lt;input type=<span class="string">"submit"</span> value=<span class="string">"修改"</span>&gt;</span><br><span class="line">    &lt;/form&gt;</span><br><span class="line"></span><br><span class="line">&lt;/div&gt;</span><br><span class="line">&lt;/body&gt;</span><br><span class="line">&lt;/html&gt;</span><br></pre></td></tr></tbody></table></figure><p>8、删除数据，BookController类编写</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 删除一本书籍</span></span><br><span class="line"><span class="meta">@RequestMapping("/deleteBook/{id}")</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> String <span class="title">deleteBook</span><span class="params">(<span class="meta">@PathVariable("id")</span> <span class="keyword">int</span> bookId)</span></span>{</span><br><span class="line">    <span class="keyword">int</span> i = bookService.deleteBookById(bookId);</span><br><span class="line">    <span class="keyword">if</span>(i == <span class="number">1</span>){</span><br><span class="line">        System.out.println(<span class="string">"删除书籍成功！"</span>);</span><br><span class="line">    }<span class="keyword">else</span>{</span><br><span class="line">        System.out.println(<span class="string">"删除书籍失败！"</span>);</span><br><span class="line">    }</span><br><span class="line">    <span class="keyword">return</span> <span class="string">"redirect:/book/allBook"</span>;</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>9、配置Tomcat，运行，测试</p><p><strong>问题说明：</strong></p><p>1、手动为项目添加lib文件夹，在其中添加项目所需要的包，否则项目会报错！</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201217214032939.png" alt="image-20201217214032939"></p><p>2、由于xml文件中使用了中文注释，需要在pom配置文件中，添加如下配置，使项目整体编码为utf-8，否则报错！</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">properties</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">project.build.sourceEncoding</span>&gt;</span>UTF8<span class="tag">&lt;/<span class="name">project.build.sourceEncoding</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">properties</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p><strong>项目结构图：</strong></p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201217214229768.png" alt="image-20201217214229768"></p><h2 id="6-JSON"><a href="#6-JSON" class="headerlink" title="6 JSON"></a>6 JSON</h2><blockquote><p>什么使 JSON ？ </p></blockquote><ul><li><p>JSON(JavaScript Object Notation, JS 对象标记) 是一种轻量级的数据交换格式，目前使用特别广泛；</p></li><li><p>采用完全独立于编程语言的<strong>文本格式</strong>来存储和表示数据。</p></li><li><p>简洁和清晰的层次结构使得 JSON 成为理想的数据交换语言。</p></li><li><p>易于人阅读和编写，同时也易于机器解析和生成，并有效地提升网络传输效率。</p></li></ul><p>在 JavaScript 语言中，一切都是对象。因此，任何JavaScript 支持的类型都可以通过 JSON 来表示，例如字符串、数字、对象、数组等。看看他的要求和语法格式：</p><ul><li>对象表示为键值对，数据由逗号分隔</li><li>花括号保存对象</li><li>方括号保存数组</li></ul><p><strong>JSON 键值对</strong>是用来保存 JavaScript 对象的一种方式，和 JavaScript 对象的写法也大同小异，键/值对组合中的键名写在前面并用双引号 “” 包裹，使用冒号 : 分隔，然后紧接着值：</p><figure class="highlight json"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">{<span class="attr">"name"</span>: <span class="string">"Zzb"</span>}</span><br><span class="line">{<span class="attr">"age"</span>: <span class="string">"1"</span>}</span><br><span class="line">{<span class="attr">"sex"</span>: <span class="string">"男"</span>}</span><br></pre></td></tr></tbody></table></figure><p>JSON 是 JavaScript 对象的字符串表示法，它使用文本表示一个 JS 对象的信息，本质是一个字符串。</p><figure class="highlight javascript"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> obj = {<span class="attr">a</span>: <span class="string">'Hello'</span>, <span class="attr">b</span>: <span class="string">'World'</span>}; <span class="comment">//这是一个对象，注意键名也是可以使用引号包裹的</span></span><br><span class="line"><span class="keyword">var</span> json = <span class="string">'{"a": "Hello", "b": "World"}'</span>; <span class="comment">//这是一个 JSON 字符串，本质是一个字符串</span></span><br></pre></td></tr></tbody></table></figure><p><strong>JSON 和 JavaScript 对象互转</strong></p><p>JSON ——&gt;  JavaScript</p><figure class="highlight javascript"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> obj = <span class="built_in">JSON</span>.parse(<span class="string">'{"a": "Hello", "b": "World"}'</span>);</span><br><span class="line"><span class="comment">//结果是 {a: 'Hello', b: 'World'}</span></span><br></pre></td></tr></tbody></table></figure><p>JavaScript ——&gt; JSON</p><figure class="highlight javascript"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> json = <span class="built_in">JSON</span>.stringify({<span class="attr">a</span>: <span class="string">'Hello'</span>, <span class="attr">b</span>: <span class="string">'World'</span>});</span><br><span class="line"><span class="comment">//结果是 '{"a": "Hello", "b": "World"}'</span></span><br></pre></td></tr></tbody></table></figure><p><strong>测试</strong></p><p>1、新建module：springmvc-05-json，添加web支持！</p><p>2、在web目录下，新建一个jsonTest1.html，编写测试内容：</p><figure class="highlight html"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;!DOCTYPE <span class="meta-keyword">html</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">html</span> <span class="attr">lang</span>=<span class="string">"en"</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">head</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">meta</span> <span class="attr">charset</span>=<span class="string">"UTF-8"</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">title</span>&gt;</span>JsonTest<span class="tag">&lt;/<span class="name">title</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">head</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">body</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;<span class="name">script</span> <span class="attr">type</span>=<span class="string">"text/javascript"</span>&gt;</span></span><br><span class="line"><span class="javascript">    <span class="comment">//编写一个js的对象</span></span></span><br><span class="line"><span class="javascript">    <span class="keyword">var</span> user = {</span></span><br><span class="line"><span class="javascript">        name:<span class="string">"Zzb"</span>,</span></span><br><span class="line">        age:1,</span><br><span class="line"><span class="javascript">        sex:<span class="string">"男"</span></span></span><br><span class="line">    };</span><br><span class="line"><span class="javascript">    <span class="comment">//将js对象转换成json字符串</span></span></span><br><span class="line"><span class="javascript">    <span class="keyword">var</span> str = <span class="built_in">JSON</span>.stringify(user);</span></span><br><span class="line"><span class="javascript">    <span class="built_in">console</span>.log(str);</span></span><br><span class="line"></span><br><span class="line"><span class="javascript">    <span class="comment">//将json字符串转换为js对象</span></span></span><br><span class="line"><span class="javascript">    <span class="keyword">var</span> user2 = <span class="built_in">JSON</span>.parse(str);</span></span><br><span class="line"><span class="javascript">    <span class="built_in">console</span>.log(user2)</span></span><br><span class="line"><span class="javascript">    <span class="built_in">console</span>.log(user2.age,user2.name,user2.sex);</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">script</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">body</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">html</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>在网页中打开，测试结果为：</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201217220934212.png" alt="image-20201217220934212"></p><blockquote><p>Controller 返回 JSON 数据</p></blockquote><p>解析工具有：Jackson、fastjson </p><p><strong>Jackson</strong></p><p>1、导入相关jar包</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind --&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>com.fasterxml.jackson.core<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>jackson-databind<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">version</span>&gt;</span>2.12.0<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>2、配置web.xml</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8"?&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">web-app</span> <span class="attr">xmlns</span>=<span class="string">"http://xmlns.jcp.org/xml/ns/javaee"</span></span></span><br><span class="line"><span class="tag">         <span class="attr">xmlns:xsi</span>=<span class="string">"http://www.w3.org/2001/XMLSchema-instance"</span></span></span><br><span class="line"><span class="tag">         <span class="attr">xsi:schemaLocation</span>=<span class="string">"http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"</span></span></span><br><span class="line"><span class="tag">         <span class="attr">version</span>=<span class="string">"4.0"</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--1 配置DispatcherServlet--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">servlet</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">servlet-name</span>&gt;</span>DispatcherServlet<span class="tag">&lt;/<span class="name">servlet-name</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">servlet-class</span>&gt;</span>org.springframework.web.servlet.DispatcherServlet<span class="tag">&lt;/<span class="name">servlet-class</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">init-param</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">param-name</span>&gt;</span>contextConfigLocation<span class="tag">&lt;/<span class="name">param-name</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">param-value</span>&gt;</span>classpath:springmvc-servlet.xml<span class="tag">&lt;/<span class="name">param-value</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">init-param</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">load-on-startup</span>&gt;</span>1<span class="tag">&lt;/<span class="name">load-on-startup</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">servlet</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">servlet-mapping</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">servlet-name</span>&gt;</span>DispatcherServlet<span class="tag">&lt;/<span class="name">servlet-name</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">url-pattern</span>&gt;</span>/<span class="tag">&lt;/<span class="name">url-pattern</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">servlet-mapping</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">filter</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">filter-name</span>&gt;</span>encoding<span class="tag">&lt;/<span class="name">filter-name</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">filter-class</span>&gt;</span>org.springframework.web.filter.CharacterEncodingFilter<span class="tag">&lt;/<span class="name">filter-class</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">init-param</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">param-name</span>&gt;</span>encoding<span class="tag">&lt;/<span class="name">param-name</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">param-value</span>&gt;</span>utf-8<span class="tag">&lt;/<span class="name">param-value</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">init-param</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">filter</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">filter-mapping</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">filter-name</span>&gt;</span>encoding<span class="tag">&lt;/<span class="name">filter-name</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">url-pattern</span>&gt;</span>/*<span class="tag">&lt;/<span class="name">url-pattern</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">filter-mapping</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">web-app</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>3、springmvc-servlet.xml</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8"?&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">beans</span> <span class="attr">xmlns</span>=<span class="string">"http://www.springframework.org/schema/beans"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xmlns:xsi</span>=<span class="string">"http://www.w3.org/2001/XMLSchema-instance"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xmlns:context</span>=<span class="string">"http://www.springframework.org/schema/context"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xmlns:mvc</span>=<span class="string">"http://www.springframework.org/schema/mvc"</span></span></span><br><span class="line"><span class="tag">       <span class="attr">xsi:schemaLocation</span>=<span class="string">"http://www.springframework.org/schema/beans</span></span></span><br><span class="line"><span class="tag"><span class="string">       http://www.springframework.org/schema/beans/spring-beans.xsd</span></span></span><br><span class="line"><span class="tag"><span class="string">       http://www.springframework.org/schema/context</span></span></span><br><span class="line"><span class="tag"><span class="string">       https://www.springframework.org/schema/context/spring-context.xsd</span></span></span><br><span class="line"><span class="tag"><span class="string">       http://www.springframework.org/schema/mvc</span></span></span><br><span class="line"><span class="tag"><span class="string">       https://www.springframework.org/schema/mvc/spring-mvc.xsd"</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--自动扫描包，让指定包下的注解生效，由IOC容器统一管理--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">context:component-scan</span> <span class="attr">base-package</span>=<span class="string">"com.zzb.controller"</span>/&gt;</span></span><br><span class="line">    <span class="comment">&lt;!--让Spring MVC不处理静态资源，例如.mp3 .css .jpg等不走视图解析器--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">mvc:default-servlet-handler</span>/&gt;</span></span><br><span class="line">    <span class="comment">&lt;!--</span></span><br><span class="line"><span class="comment">       支持mvc注解驱动</span></span><br><span class="line"><span class="comment">       在spring中一般采用@RequestMapping注解来完成映射关系</span></span><br><span class="line"><span class="comment">       要想使@RequestMapping注解生效</span></span><br><span class="line"><span class="comment">       必须向上下文中注册DefaultAnnotationHandlerMapping</span></span><br><span class="line"><span class="comment">       和一个AnnotationMethodHandlerAdapter实例</span></span><br><span class="line"><span class="comment">       这两个实例分别在类级别和方法级别处理。</span></span><br><span class="line"><span class="comment">       而annotation-driven配置帮助我们自动完成上述两个实例的注入</span></span><br><span class="line"><span class="comment">    --&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">mvc:annotation-driven</span>/&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--视图解析器--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">bean</span> <span class="attr">class</span>=<span class="string">"org.springframework.web.servlet.view.InternalResourceViewResolver"</span> <span class="attr">id</span>=<span class="string">"internalResourceViewResolver"</span>&gt;</span></span><br><span class="line">        <span class="comment">&lt;!--前缀--&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"prefix"</span> <span class="attr">value</span>=<span class="string">"/WEB-INF/jsp/"</span>/&gt;</span></span><br><span class="line">        <span class="comment">&lt;!--后缀--&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"suffix"</span> <span class="attr">value</span>=<span class="string">".jsp"</span>/&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">bean</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">beans</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>4、实体类</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.pojo;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">User</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> String name;</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">int</span> age;</span><br><span class="line">    <span class="keyword">private</span> String sex;</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="title">User</span><span class="params">()</span> </span>{</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="title">User</span><span class="params">(String name, <span class="keyword">int</span> age, String sex)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.name = name;</span><br><span class="line">        <span class="keyword">this</span>.age = age;</span><br><span class="line">        <span class="keyword">this</span>.sex = sex;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">getName</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> name;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setName</span><span class="params">(String name)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.name = name;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">getAge</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> age;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setAge</span><span class="params">(<span class="keyword">int</span> age)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.age = age;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">getSex</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> sex;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setSex</span><span class="params">(String sex)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.sex = sex;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">toString</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> <span class="string">"User{"</span> +</span><br><span class="line">                <span class="string">"name='"</span> + name + <span class="string">'\''</span> +</span><br><span class="line">                <span class="string">", age="</span> + age +</span><br><span class="line">                <span class="string">", sex='"</span> + sex + <span class="string">'\''</span> +</span><br><span class="line">                <span class="string">'}'</span>;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>5、编写Controller</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.controller;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> com.fasterxml.jackson.core.JsonProcessingException;</span><br><span class="line"><span class="keyword">import</span> com.fasterxml.jackson.databind.ObjectMapper;</span><br><span class="line"><span class="keyword">import</span> com.zzb.pojo.User;</span><br><span class="line"><span class="keyword">import</span> org.springframework.stereotype.Controller;</span><br><span class="line"><span class="keyword">import</span> org.springframework.web.bind.annotation.RequestMapping;</span><br><span class="line"><span class="keyword">import</span> org.springframework.web.bind.annotation.ResponseBody;</span><br><span class="line"></span><br><span class="line"><span class="meta">@Controller</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">UserController</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="meta">@RequestMapping("/json1")</span></span><br><span class="line">    <span class="meta">@ResponseBody</span> <span class="comment">// 该注解声明返回结果是响应体，不会走视图解析器</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">jsonTest1</span><span class="params">()</span> <span class="keyword">throws</span> JsonProcessingException </span>{</span><br><span class="line">        <span class="comment">// 创建一个jackson的对象映射器，用来解析数据</span></span><br><span class="line">        ObjectMapper mapper = <span class="keyword">new</span> ObjectMapper();</span><br><span class="line">        <span class="comment">// 创建一个对象</span></span><br><span class="line">        User user = <span class="keyword">new</span> User(<span class="string">"Zzb1号"</span>, <span class="number">1</span>, <span class="string">"男"</span>);</span><br><span class="line">        String str = mapper.writeValueAsString(user);</span><br><span class="line">        <span class="keyword">return</span> str;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>6、配置Tomcat，注意项目中添加lib文件，并在其中添加依赖！</p><p>测试：</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201217223843923.png" alt="image-20201217223843923"></p><p>出现乱码问题！</p><p>需要设置一下编码格式（utf-8），以及返回的类型！</p><p>通过@RequestMaping的produces属性来实现，修改下代码</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//produces:指定响应体返回类型和编码</span></span><br><span class="line"><span class="meta">@RequestMapping(value = "/json1",produces = "application/json;charset=utf-8")</span></span><br></pre></td></tr></tbody></table></figure><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201217224109783.png" alt="image-20201217224109783"></p><p>乱码问题解决！</p><blockquote><p>代码优化</p></blockquote><p><strong>乱码统一解决</strong></p><p>每次使用上述方法解决乱码问题比较麻烦，可以通过Spring配置统一指定！在springmvc的核心配置文件中添加StringHttpMessageConverter转换配置！</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">mvc:annotation-driven</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">mvc:message-converters</span> <span class="attr">register-defaults</span>=<span class="string">"true"</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">bean</span> <span class="attr">class</span>=<span class="string">"org.springframework.http.converter.StringHttpMessageConverter"</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">constructor-arg</span> <span class="attr">value</span>=<span class="string">"UTF-8"</span>/&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">bean</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">bean</span> <span class="attr">class</span>=<span class="string">"org.springframework.http.converter.json.MappingJackson2HttpMessageConverter"</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"objectMapper"</span>&gt;</span></span><br><span class="line">                <span class="tag">&lt;<span class="name">bean</span> <span class="attr">class</span>=<span class="string">"org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean"</span>&gt;</span></span><br><span class="line">                    <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"failOnEmptyBeans"</span> <span class="attr">value</span>=<span class="string">"false"</span>/&gt;</span></span><br><span class="line">                <span class="tag">&lt;/<span class="name">bean</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;/<span class="name">property</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">bean</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">mvc:message-converters</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">mvc:annotation-driven</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p><strong>返回响应体</strong></p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">   <span class="meta">@RequestMapping("/json1")</span></span><br><span class="line">   <span class="meta">@ResponseBody</span> <span class="comment">// 该注解声明返回结果是响应体，不会走视图解析器</span></span><br><span class="line"><span class="meta">@RestController</span> <span class="comment">// 可以在类上直接使用该注解，该类的所有方法都只会返回响应体，不需要每个方法都添加 @ResponseBody 注解</span></span><br></pre></td></tr></tbody></table></figure><p>测试：</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201217225042621.png" alt="image-20201217225042621"></p><blockquote><p>集合转JSON</p></blockquote><p>添加类方法</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@RequestMapping("/json2")</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> String <span class="title">jsonTest2</span><span class="params">()</span> <span class="keyword">throws</span> JsonProcessingException </span>{</span><br><span class="line">    <span class="comment">// 创建一个jackson的对象映射器，用来解析数据</span></span><br><span class="line">    ObjectMapper mapper = <span class="keyword">new</span> ObjectMapper();</span><br><span class="line">    <span class="comment">// 创建一个对象</span></span><br><span class="line">    User user1 = <span class="keyword">new</span> User(<span class="string">"Zzb1号"</span>, <span class="number">1</span>, <span class="string">"男"</span>);</span><br><span class="line">    User user2 = <span class="keyword">new</span> User(<span class="string">"Zzb2号"</span>, <span class="number">2</span>, <span class="string">"男"</span>);</span><br><span class="line">    User user3 = <span class="keyword">new</span> User(<span class="string">"Zzb3号"</span>, <span class="number">3</span>, <span class="string">"男"</span>);</span><br><span class="line">    User user4 = <span class="keyword">new</span> User(<span class="string">"Zzb4号"</span>, <span class="number">4</span>, <span class="string">"男"</span>);</span><br><span class="line"></span><br><span class="line">    List&lt;User&gt; list = <span class="keyword">new</span> ArrayList&lt;User&gt;();</span><br><span class="line">    list.add(user1);</span><br><span class="line">    list.add(user2);</span><br><span class="line">    list.add(user3);</span><br><span class="line">    list.add(user4);</span><br><span class="line"></span><br><span class="line">    String str = mapper.writeValueAsString(list);</span><br><span class="line">    <span class="keyword">return</span> str;</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>测试：</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201217225403269.png" alt="image-20201217225403269"></p><blockquote><p>输出时间对象</p></blockquote><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> String <span class="title">jsonTest3</span><span class="params">()</span> <span class="keyword">throws</span> JsonProcessingException </span>{</span><br><span class="line">    <span class="comment">// 创建一个jackson的对象映射器，用来解析数据</span></span><br><span class="line">    ObjectMapper mapper = <span class="keyword">new</span> ObjectMapper();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 创建一个时间对象</span></span><br><span class="line">    Date date = <span class="keyword">new</span> Date();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 显示结果为时间戳</span></span><br><span class="line">    String str = mapper.writeValueAsString(date);</span><br><span class="line">    <span class="keyword">return</span> str;</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>测试：</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201217225657005.png" alt="image-20201217225657005"></p><ul><li>默认日期格式会变成一个数字，是1970年1月1日到当前日期的毫秒数！</li><li>Jackson 默认是会把时间转成timestamps形式</li></ul><p><strong>自定义时间格式</strong></p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@RequestMapping("/json4")</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> String <span class="title">jsonTest4</span><span class="params">()</span> <span class="keyword">throws</span> JsonProcessingException </span>{</span><br><span class="line">    <span class="comment">// 创建一个jackson的对象映射器，用来解析数据</span></span><br><span class="line">    ObjectMapper mapper = <span class="keyword">new</span> ObjectMapper();</span><br><span class="line">    <span class="comment">// 不使用时间戳的方式</span></span><br><span class="line">    mapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, <span class="keyword">false</span>);</span><br><span class="line">    <span class="comment">// 自定义时间格式</span></span><br><span class="line">    SimpleDateFormat sdf = <span class="keyword">new</span> SimpleDateFormat(<span class="string">"yyyy-MM-dd HH:mm:ss"</span>);</span><br><span class="line">    <span class="comment">// 设置时间格式</span></span><br><span class="line">    mapper.setDateFormat(sdf);</span><br><span class="line">    <span class="comment">// 创建一个时间对象</span></span><br><span class="line">    Date date = <span class="keyword">new</span> Date();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 显示结果为时间戳</span></span><br><span class="line">    String str = mapper.writeValueAsString(date);</span><br><span class="line">    <span class="keyword">return</span> str;</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>测试：</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201217230215694.png" alt="image-20201217230215694"></p><blockquote><p>抽取为工具类</p></blockquote><p>将JSON的转换封装成工具类</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.utils;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> com.fasterxml.jackson.core.JsonProcessingException;</span><br><span class="line"><span class="keyword">import</span> com.fasterxml.jackson.databind.ObjectMapper;</span><br><span class="line"><span class="keyword">import</span> com.fasterxml.jackson.databind.SerializationFeature;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> java.text.SimpleDateFormat;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">JsonUtils</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> String <span class="title">getJson</span><span class="params">(Object object)</span></span>{</span><br><span class="line">        <span class="keyword">return</span> getJson(object,<span class="string">"yyyy-MM-dd HH:mm:ss"</span>);</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> String <span class="title">getJson</span><span class="params">(Object object, String dateFormat)</span></span>{</span><br><span class="line">        <span class="comment">// 创建一个jackson的对象映射器，用来解析数据</span></span><br><span class="line">        ObjectMapper mapper = <span class="keyword">new</span> ObjectMapper();</span><br><span class="line">        <span class="comment">// 不使用时间戳的方式</span></span><br><span class="line">        mapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, <span class="keyword">false</span>);</span><br><span class="line">        <span class="comment">// 自定义时间格式</span></span><br><span class="line">        SimpleDateFormat sdf = <span class="keyword">new</span> SimpleDateFormat(<span class="string">"dateFormat"</span>);</span><br><span class="line">        <span class="comment">// 设置时间格式</span></span><br><span class="line">        mapper.setDateFormat(sdf);</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 显示结果为时间戳</span></span><br><span class="line">        String str = <span class="keyword">null</span>;</span><br><span class="line">        <span class="keyword">try</span> {</span><br><span class="line">            str = mapper.writeValueAsString(object);</span><br><span class="line">        } <span class="keyword">catch</span> (JsonProcessingException e) {</span><br><span class="line">            e.printStackTrace();</span><br><span class="line">        }</span><br><span class="line">        <span class="keyword">return</span> str;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>使用工具类编写代码</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@RequestMapping("/json5")</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> String <span class="title">jsonTest5</span><span class="params">()</span></span>{</span><br><span class="line">    Date date = <span class="keyword">new</span> Date();</span><br><span class="line">    String json = JsonUtils.getJson(date);</span><br><span class="line">    <span class="keyword">return</span> json;</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>测试：</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201217232330324.png" alt="image-20201217232330324"></p><blockquote><p>FastJson</p></blockquote><p>FastJson 由阿里巴巴开发，专门用于java的包，可以方便的实现json对象与JavaBean对象的转换，实现JavaBean对象与json字符串的转换，实现json对象与json字符串的转换。实现json的转换方法很多，最后的实现结果都是一样的。</p><p>jar包</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">   <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>com.alibaba<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">   <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>fastjson<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">   <span class="tag">&lt;<span class="name">version</span>&gt;</span>1.2.60<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>FastJson 三个主要的类：</p><p><strong>JSONObject  代表 json 对象</strong> </p><ul><li>JSONObject实现了Map接口, JSONObject底层操作是由Map实现的。</li><li>JSONObject对应json对象，通过各种形式的get()方法可以获取json对象中的数据，也可利用诸如size()，isEmpty()等方法获取”键：值”对的个数和判断是否为空。其本质是通过实现Map接口并调用接口中的方法完成的。</li></ul><p><strong>JSONArray  代表 json 对象数组</strong></p><ul><li>内部是有List接口中的方法来完成操作的。</li></ul><p><strong>JSON代表 JSONObject和JSONArray的转化</strong></p><ul><li>仔细观察这些方法，主要是实现json对象，json对象数组，javabean对象，json字符串之间的相互转化。</li></ul><p>代码测试：</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.controller;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> com.alibaba.fastjson.JSON;</span><br><span class="line"><span class="keyword">import</span> com.alibaba.fastjson.JSONObject;</span><br><span class="line"><span class="keyword">import</span> com.zzb.pojo.User;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> java.util.ArrayList;</span><br><span class="line"><span class="keyword">import</span> java.util.List;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">FastJsonTest</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String[] args)</span> </span>{</span><br><span class="line">        <span class="comment">// 创建对象</span></span><br><span class="line">        User user1 = <span class="keyword">new</span> User(<span class="string">"Zzb1号"</span>, <span class="number">1</span>, <span class="string">"男"</span>);</span><br><span class="line">        User user2 = <span class="keyword">new</span> User(<span class="string">"Zzb2号"</span>, <span class="number">2</span>, <span class="string">"男"</span>);</span><br><span class="line">        User user3 = <span class="keyword">new</span> User(<span class="string">"Zzb3号"</span>, <span class="number">3</span>, <span class="string">"男"</span>);</span><br><span class="line">        User user4 = <span class="keyword">new</span> User(<span class="string">"Zzb4号"</span>, <span class="number">4</span>, <span class="string">"男"</span>);</span><br><span class="line"></span><br><span class="line">        List&lt;User&gt; list = <span class="keyword">new</span> ArrayList&lt;User&gt;();</span><br><span class="line">        list.add(user1);</span><br><span class="line">        list.add(user2);</span><br><span class="line">        list.add(user3);</span><br><span class="line">        list.add(user4);</span><br><span class="line"></span><br><span class="line">        System.out.println(<span class="string">"java对象转json字符串"</span>);</span><br><span class="line">        String str1 = JSON.toJSONString(list);</span><br><span class="line">        System.out.println(<span class="string">"java -&gt; json (list)"</span> + str1);</span><br><span class="line">        String str2 = JSON.toJSONString(user1);</span><br><span class="line">        System.out.println(<span class="string">"java -&gt; json (user1)"</span> + str1);</span><br><span class="line"></span><br><span class="line">        System.out.println(<span class="string">"json字符串转java对象"</span>);</span><br><span class="line">        User jUser1 = JSON.parseObject(str2, User.class);</span><br><span class="line">        System.out.println(<span class="string">"jUser1"</span> + jUser1.toString());</span><br><span class="line"></span><br><span class="line">        System.out.println(<span class="string">"java对象转json对象"</span>);</span><br><span class="line">        JSONObject jsonObject1 = (JSONObject) JSON.toJSON(user2);</span><br><span class="line">        System.out.println(<span class="string">"JSONObject (user2)"</span> + jsonObject1.getString(<span class="string">"name"</span>));</span><br><span class="line"></span><br><span class="line">        System.out.println(<span class="string">"json对象转java对象"</span>);</span><br><span class="line">        User jUser2 = JSON.toJavaObject(jsonObject1, User.class);</span><br><span class="line">        System.out.println(<span class="string">"jUser2 :"</span> + jUser2.toString());</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>测试结果：</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201217233501499.png" alt="image-20201217233501499"></p><h2 id="7-Ajax"><a href="#7-Ajax" class="headerlink" title="7 Ajax"></a>7 Ajax</h2><blockquote><p>简介</p></blockquote><ul><li><p><strong>AJAX = Asynchronous JavaScript and XML（异步的 JavaScript 和 XML）。</strong> </p></li><li><p>AJAX 是一种在无需重新加载整个网页的情况下，能够更新部分网页的技术。</p></li><li><p><strong>Ajax 不是一种新的编程语言，而是一种用于创建更好更快以及交互性更强的Web应用程序的技术。</strong></p></li><li><p>在 2005 年，Google 通过其 Google Suggest 使 AJAX 变得流行起来。Google Suggest能够自动帮你完成搜索单词。</p></li><li><p>Google Suggest 使用 AJAX 创造出动态性极强的 web 界面：当您在谷歌的搜索框输入关键字时，JavaScript 会把这些字符发送到服务器，然后服务器会返回一个搜索建议的列表。</p></li><li><p>传统的网页（即不使用ajax技术的网页），想要更新内容或者提交一个表单，都需要重新加载整个网页。</p></li><li><p>使用ajax技术的网页，通过在后台服务器进行少量的数据交换，就可以实现异步局部更新。</p></li><li><p>使用Ajax，用户可以创建接近本地桌面应用的直接、高可用、更丰富、更动态的Web用户界面。</p></li></ul><blockquote><p>伪造Ajax</p></blockquote><p>1、新建module springmvc-06-ajax，导入web支持，测试项目，是否能成功运行！</p><p>2、编写一个 test.html 使用 iframe测试</p><figure class="highlight html"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;!DOCTYPE <span class="meta-keyword">html</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">html</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">head</span> <span class="attr">lang</span>=<span class="string">"en"</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">meta</span> <span class="attr">charset</span>=<span class="string">"UTF-8"</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">title</span>&gt;</span>伪造AJAX<span class="tag">&lt;/<span class="name">title</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">head</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">body</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;<span class="name">script</span> <span class="attr">type</span>=<span class="string">"text/javascript"</span>&gt;</span></span><br><span class="line"><span class="javascript">    <span class="built_in">window</span>.onload = <span class="function"><span class="keyword">function</span>(<span class="params"></span>)</span>{</span></span><br><span class="line"><span class="javascript">        <span class="keyword">var</span> myDate = <span class="keyword">new</span> <span class="built_in">Date</span>();</span></span><br><span class="line"><span class="javascript">        <span class="built_in">document</span>.getElementById(<span class="string">'currentTime'</span>).innerText = myDate.getTime();</span></span><br><span class="line">    };</span><br><span class="line"></span><br><span class="line"><span class="javascript">    <span class="function"><span class="keyword">function</span> <span class="title">LoadPage</span>(<span class="params"></span>)</span>{</span></span><br><span class="line"><span class="javascript">        <span class="keyword">var</span> targetUrl =  <span class="built_in">document</span>.getElementById(<span class="string">'url'</span>).value;</span></span><br><span class="line"><span class="javascript">        <span class="built_in">console</span>.log(targetUrl);</span></span><br><span class="line"><span class="javascript">        <span class="built_in">document</span>.getElementById(<span class="string">"iframePosition"</span>).src = targetUrl;</span></span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">script</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;<span class="name">div</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">p</span>&gt;</span>请输入要加载的地址：<span class="tag">&lt;<span class="name">span</span> <span class="attr">id</span>=<span class="string">"currentTime"</span>&gt;</span><span class="tag">&lt;/<span class="name">span</span>&gt;</span><span class="tag">&lt;/<span class="name">p</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">p</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">input</span> <span class="attr">id</span>=<span class="string">"url"</span> <span class="attr">type</span>=<span class="string">"text"</span> <span class="attr">value</span>=<span class="string">"https://www.baidu.com/"</span>/&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">input</span> <span class="attr">type</span>=<span class="string">"button"</span> <span class="attr">value</span>=<span class="string">"提交"</span> <span class="attr">onclick</span>=<span class="string">"LoadPage()"</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">p</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">div</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;<span class="name">div</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">h3</span>&gt;</span>加载页面位置：<span class="tag">&lt;/<span class="name">h3</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">iframe</span> <span class="attr">id</span>=<span class="string">"iframePosition"</span> <span class="attr">style</span>=<span class="string">"width: 100%;height: 500px;"</span>&gt;</span><span class="tag">&lt;/<span class="name">iframe</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">div</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">body</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">html</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>3、在IDEA中打开浏览器查看效果！</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20210106135930189.png" alt="image-20210106135930189"></p><p><strong>利用AJAX可以做：</strong></p><ul><li>注册时，检测用户名是否已注册</li><li>登录时，提示用户名密码错误</li><li>等等</li></ul><blockquote><p>jQuery.ajax</p></blockquote><ul><li><p>这里使用jquery来实现ajax； </p></li><li><p>Ajax的核心是XMLHttpRequest对象(XHR)。XHR为向服务器发送请求和解析服务器响应提供了接口。能够以异步方式从服务器获取新数据；</p></li><li><p>jQuery 提供多个与 AJAX 有关的方法；</p></li><li><p>通过jQuery.AJAX方法，可以使用HTTP GET 何HTTP POST从远程服务器上请求文本、HTML、XML活JSON，同时也可以把这些外部数据直接载入网页的被选元素中;</p></li><li><p>jQuery 不是生产者，而是大自然搬运工;</p></li><li><p>jQuery Ajax本质就是 XMLHttpRequest，对他进行了封装，方便调用！</p></li></ul><figure class="highlight javascript"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line">jQuery.ajax(...)</span><br><span class="line">      部分参数：</span><br><span class="line">            url：请求地址</span><br><span class="line">            type：请求方式，GET、POST（<span class="number">1.9</span><span class="number">.0</span>之后用method）</span><br><span class="line">        headers：请求头</span><br><span class="line">            data：要发送的数据</span><br><span class="line">    contentType：即将发送信息至服务器的内容编码类型(默认: <span class="string">"application/x-www-form-urlencoded; charset=UTF-8"</span>)</span><br><span class="line">          <span class="keyword">async</span>：是否异步</span><br><span class="line">        timeout：设置请求超时时间（毫秒）</span><br><span class="line">      beforeSend：发送请求前执行的函数(全局)</span><br><span class="line">        complete：完成之后执行的回调函数(全局)</span><br><span class="line">        success：成功之后执行的回调函数(全局)</span><br><span class="line">          error：失败之后执行的回调函数(全局)</span><br><span class="line">        accepts：通过请求头发送给服务器，告诉服务器当前客户端可接受的数据类型</span><br><span class="line">        dataType：将服务器端返回的数据转换成指定类型</span><br><span class="line">          <span class="string">"xml"</span>: 将服务器端返回的内容转换成xml格式</span><br><span class="line">          <span class="string">"text"</span>: 将服务器端返回的内容转换成普通文本格式</span><br><span class="line">          <span class="string">"html"</span>: 将服务器端返回的内容转换成普通文本格式，在插入DOM中时，如果包含JavaScript标签，则会尝试去执行。</span><br><span class="line">        <span class="string">"script"</span>: 尝试将返回值当作JavaScript去执行，然后再将服务器端返回的内容转换成普通文本格式</span><br><span class="line">          <span class="string">"json"</span>: 将服务器端返回的内容转换成相应的JavaScript对象</span><br><span class="line">        <span class="string">"jsonp"</span>: JSONP 格式使用 JSONP 形式调用函数时，如 <span class="string">"myurl?callback=?"</span> jQuery 将自动替换 ? 为正确的函数名，以执行回调函数</span><br></pre></td></tr></tbody></table></figure><p><strong>使用 HttpServletResponse 处理，实现简单的测试！</strong></p><p>1、配置 web.xml 和 springmvc 的配置文件。</p><p>2、编写一个AjaxController</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.controller;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> org.springframework.web.bind.annotation.RequestMapping;</span><br><span class="line"><span class="keyword">import</span> org.springframework.web.bind.annotation.RestController;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> javax.servlet.http.HttpServletResponse;</span><br><span class="line"><span class="keyword">import</span> java.io.IOException;</span><br><span class="line"></span><br><span class="line"><span class="meta">@RestController</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">AjaxController</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="meta">@RequestMapping("/a1")</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">a1</span><span class="params">(String name, HttpServletResponse response)</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line">        System.out.println(<span class="string">"a1:param=&gt;"</span> + name);</span><br><span class="line">        <span class="keyword">if</span>(<span class="string">"admin"</span>.equals(name)){</span><br><span class="line">            response.getWriter().print(<span class="string">"true"</span>);</span><br><span class="line">        }<span class="keyword">else</span>{</span><br><span class="line">            response.getWriter().print(<span class="string">"false"</span>);</span><br><span class="line">        }</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>3、编写index.jsp</p><figure class="highlight"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br></pre></td><td class="code"><pre><span class="line">&lt;%@ page contentType=<span class="string">"text/html;charset=UTF-8"</span> language=<span class="string">"java"</span> %&gt;</span><br><span class="line">&lt;html&gt;</span><br><span class="line">  &lt;head&gt;</span><br><span class="line">    &lt;title&gt;$Title$&lt;/title&gt;</span><br><span class="line">    &lt;%--导入在线jquery--%&gt;</span><br><span class="line">    &lt;script src="${pageContext.request.contextPath}/statics/js/jquery-3.5.1.js"&gt;&lt;/script&gt;</span><br><span class="line"></span><br><span class="line">    &lt;script&gt;</span><br><span class="line">      <span class="function">function <span class="title">a</span><span class="params">()</span></span>{</span><br><span class="line">        $.post({</span><br><span class="line">          url:<span class="string">"${pageContext.request.contextPath}/a1"</span>,</span><br><span class="line">          data:{<span class="string">'name'</span>:$(<span class="string">"#txtName"</span>).val()},</span><br><span class="line">          success:function (data){</span><br><span class="line">            alert(data);</span><br><span class="line">          }</span><br><span class="line">        });</span><br><span class="line">      }</span><br><span class="line">    &lt;/script&gt;</span><br><span class="line"></span><br><span class="line">  &lt;/head&gt;</span><br><span class="line">  &lt;body&gt;</span><br><span class="line"></span><br><span class="line">  &lt;%--失去焦点触发事件--%&gt;</span><br><span class="line">  用户名：&lt;input type=<span class="string">"text"</span> id=<span class="string">"txtName"</span> onblur=<span class="string">"a()"</span>&gt;</span><br><span class="line">  &lt;/body&gt;</span><br><span class="line">&lt;/html&gt;</span><br></pre></td></tr></tbody></table></figure><p>4、启动tomcat测试</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20210106191523577.png" alt="image-20210106191523577"></p><p><strong>SpringMVC实现</strong></p><p>1、实体类</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.pojo;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">User</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> String name;</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">int</span> age;</span><br><span class="line">    <span class="keyword">private</span> String sex;</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="title">User</span><span class="params">()</span> </span>{</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="title">User</span><span class="params">(String name, <span class="keyword">int</span> age, String sex)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.name = name;</span><br><span class="line">        <span class="keyword">this</span>.age = age;</span><br><span class="line">        <span class="keyword">this</span>.sex = sex;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">getName</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> name;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setName</span><span class="params">(String name)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.name = name;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">getAge</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> age;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setAge</span><span class="params">(<span class="keyword">int</span> age)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.age = age;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">getSex</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> sex;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setSex</span><span class="params">(String sex)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.sex = sex;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">toString</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> <span class="string">"User{"</span> +</span><br><span class="line">                <span class="string">"name='"</span> + name + <span class="string">'\''</span> +</span><br><span class="line">                <span class="string">", age="</span> + age +</span><br><span class="line">                <span class="string">", sex='"</span> + sex + <span class="string">'\''</span> +</span><br><span class="line">                <span class="string">'}'</span>;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>2、Controller类编写</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@RequestMapping("/a2")</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> List&lt;User&gt; <span class="title">a2</span><span class="params">()</span></span>{</span><br><span class="line">    List&lt;User&gt; userList = <span class="keyword">new</span> ArrayList&lt;User&gt;();</span><br><span class="line">    userList.add(<span class="keyword">new</span> User(<span class="string">"Zzb1号"</span>,<span class="number">1</span>,<span class="string">"男"</span>));</span><br><span class="line">    userList.add(<span class="keyword">new</span> User(<span class="string">"Zzb2号"</span>,<span class="number">2</span>,<span class="string">"男"</span>));</span><br><span class="line">    userList.add(<span class="keyword">new</span> User(<span class="string">"Zzb3号"</span>,<span class="number">3</span>,<span class="string">"男"</span>));</span><br><span class="line">    <span class="keyword">return</span> userList; <span class="comment">// 由于@RestController注解，将list转成json格式返回</span></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>3、前端页面</p><figure class="highlight"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br></pre></td><td class="code"><pre><span class="line">&lt;%@ page contentType=<span class="string">"text/html;charset=UTF-8"</span> language=<span class="string">"java"</span> %&gt;</span><br><span class="line">&lt;html&gt;</span><br><span class="line">&lt;head&gt;</span><br><span class="line">    &lt;title&gt;Title&lt;/title&gt;</span><br><span class="line">    &lt;script src="${pageContext.request.contextPath}/statics/js/jquery-3.5.1.js"&gt;&lt;/script&gt;</span><br><span class="line"></span><br><span class="line">&lt;/head&gt;</span><br><span class="line">&lt;body&gt;</span><br><span class="line"></span><br><span class="line">&lt;input type=<span class="string">"button"</span> id=<span class="string">"btn"</span> value=<span class="string">"获取数据"</span>/&gt;</span><br><span class="line">&lt;table width=<span class="string">"80%"</span> align=<span class="string">"center"</span>&gt;</span><br><span class="line">    &lt;tr&gt;</span><br><span class="line">        &lt;td&gt;姓名&lt;/td&gt;</span><br><span class="line">        &lt;td&gt;年龄&lt;/td&gt;</span><br><span class="line">        &lt;td&gt;性别&lt;/td&gt;</span><br><span class="line">    &lt;/tr&gt;</span><br><span class="line">    &lt;tbody id=<span class="string">"content"</span>&gt;</span><br><span class="line"></span><br><span class="line">    &lt;/tbody&gt;</span><br><span class="line">&lt;/table&gt;</span><br><span class="line"></span><br><span class="line">&lt;script&gt;</span><br><span class="line">    $(<span class="string">"#btn"</span>).click(function (){</span><br><span class="line">        $.post(<span class="string">"${pageContext.request.contextPath}/a2"</span>, function (data){</span><br><span class="line">            console.log(data)</span><br><span class="line">            <span class="keyword">var</span> html = <span class="string">""</span>;</span><br><span class="line">            <span class="keyword">for</span>(<span class="keyword">var</span> i = <span class="number">0</span>; i &lt; data.length; ++i){</span><br><span class="line">                html+=<span class="string">"&lt;tr&gt;"</span> + <span class="string">"&lt;td&gt;"</span> + data[i].name + <span class="string">"&lt;/td&gt;"</span> + <span class="string">"&lt;td&gt;"</span> + data[i].age + <span class="string">"&lt;/td&gt;"</span> + <span class="string">"&lt;td&gt;"</span> + data[i].sex + <span class="string">"&lt;/td&gt;"</span> + <span class="string">"&lt;/tr&gt;"</span></span><br><span class="line">            }</span><br><span class="line"></span><br><span class="line">            $(<span class="string">"#content"</span>).html(html);</span><br><span class="line">        })</span><br><span class="line">    })</span><br><span class="line">&lt;/script&gt;</span><br><span class="line"></span><br><span class="line">&lt;/body&gt;</span><br><span class="line">&lt;/html&gt;</span><br></pre></td></tr></tbody></table></figure><p>4、测试</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20210106193750816.png" alt="image-20210106193750816"></p><blockquote><p>注册提示效果</p></blockquote><p>1、编写Controller类</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@RequestMapping("/a3")</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> String <span class="title">a3</span><span class="params">(String name)</span></span>{</span><br><span class="line">    String msg = <span class="string">""</span>;</span><br><span class="line">    <span class="comment">// 模拟数据库中存在数据</span></span><br><span class="line">    <span class="keyword">if</span>(name != <span class="keyword">null</span>){</span><br><span class="line">        <span class="keyword">if</span>(<span class="string">"admin"</span>.equals(name)){</span><br><span class="line">            msg = <span class="string">"ok"</span>;</span><br><span class="line">        }<span class="keyword">else</span>{</span><br><span class="line">            msg = <span class="string">"用户名不存在！"</span>;</span><br><span class="line">        }</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> msg;</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>2、前端页面</p><figure class="highlight"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br></pre></td><td class="code"><pre><span class="line">&lt;%@ page contentType=<span class="string">"text/html;charset=UTF-8"</span> language=<span class="string">"java"</span> %&gt;</span><br><span class="line">&lt;html&gt;</span><br><span class="line">&lt;head&gt;</span><br><span class="line">    &lt;title&gt;Title&lt;/title&gt;</span><br><span class="line">    &lt;script src="${pageContext.request.contextPath}/statics/js/jquery-3.5.1.js"&gt;&lt;/script&gt;</span><br><span class="line">&lt;/head&gt;</span><br><span class="line">&lt;body&gt;</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">&lt;p&gt;</span><br><span class="line">    用户名：&lt;input type=<span class="string">"text"</span> id=<span class="string">"name"</span> onblur=<span class="string">"a()"</span>&gt;</span><br><span class="line">    &lt;span id="userInfo"&gt;&lt;/span&gt;</span><br><span class="line">&lt;/p&gt;</span><br><span class="line">&lt;p&gt;</span><br><span class="line">    密码：&lt;input type=<span class="string">"password"</span> id=<span class="string">"pwd"</span> onblur=<span class="string">"a()"</span>&gt;</span><br><span class="line">&lt;/p&gt;</span><br><span class="line"></span><br><span class="line">&lt;script&gt;</span><br><span class="line">    <span class="function">function <span class="title">a</span><span class="params">()</span></span>{</span><br><span class="line">        $.post({</span><br><span class="line">            url:<span class="string">"${pageContext.request.contextPath}/a3"</span>,</span><br><span class="line">            data:{<span class="string">'name'</span>:$(<span class="string">"#name"</span>).val()},</span><br><span class="line">            success:function (data){</span><br><span class="line">                console.log(data);</span><br><span class="line">                <span class="keyword">if</span>(data.toString() == <span class="string">"ok"</span>){</span><br><span class="line">                    $(<span class="string">"#userInfo"</span>).css(<span class="string">"color"</span>, <span class="string">"green"</span>);</span><br><span class="line">                }<span class="keyword">else</span>{</span><br><span class="line">                    $(<span class="string">"#userInfo"</span>).css(<span class="string">"color"</span>, <span class="string">"red"</span>);</span><br><span class="line">                }</span><br><span class="line">                $(<span class="string">"#userInfo"</span>).html(data);</span><br><span class="line">            }</span><br><span class="line">        });</span><br><span class="line">    }</span><br><span class="line">&lt;/script&gt;</span><br><span class="line"></span><br><span class="line">&lt;/body&gt;</span><br><span class="line">&lt;/html&gt;</span><br></pre></td></tr></tbody></table></figure><p>注意：因为传递的是json对象，所以要处理json字符串的乱码问题</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">mvc:annotation-driven</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">mvc:message-converters</span> <span class="attr">register-defaults</span>=<span class="string">"true"</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">bean</span> <span class="attr">class</span>=<span class="string">"org.springframework.http.converter.StringHttpMessageConverter"</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">constructor-arg</span> <span class="attr">value</span>=<span class="string">"UTF-8"</span>/&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">bean</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">bean</span> <span class="attr">class</span>=<span class="string">"org.springframework.http.converter.json.MappingJackson2HttpMessageConverter"</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"objectMapper"</span>&gt;</span></span><br><span class="line">                <span class="tag">&lt;<span class="name">bean</span> <span class="attr">class</span>=<span class="string">"org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean"</span>&gt;</span></span><br><span class="line">                    <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"failOnEmptyBeans"</span> <span class="attr">value</span>=<span class="string">"false"</span>/&gt;</span></span><br><span class="line">                <span class="tag">&lt;/<span class="name">bean</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;/<span class="name">property</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">bean</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">mvc:message-converters</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">mvc:annotation-driven</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>3、测试</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20210106195420085.png" alt="image-20210106195420085"></p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20210106195432238.png" alt="image-20210106195432238"></p><blockquote><p>获取百度接口Demo</p></blockquote><figure class="highlight html"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;!DOCTYPE <span class="meta-keyword">HTML</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">html</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">head</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">meta</span> <span class="attr">http-equiv</span>=<span class="string">"Content-Type"</span> <span class="attr">content</span>=<span class="string">"text/html; charset=utf-8"</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">title</span>&gt;</span>JSONP百度搜索<span class="tag">&lt;/<span class="name">title</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">style</span>&gt;</span></span><br><span class="line">        #q{</span><br><span class="line"><span class="css">            <span class="attribute">width</span>: <span class="number">500px</span>;</span></span><br><span class="line"><span class="css">            <span class="attribute">height</span>: <span class="number">30px</span>;</span></span><br><span class="line"><span class="css">            <span class="attribute">border</span>:<span class="number">1px</span> solid <span class="number">#ddd</span>;</span></span><br><span class="line"><span class="css">            <span class="attribute">line-height</span>: <span class="number">30px</span>;</span></span><br><span class="line"><span class="css">            <span class="attribute">display</span>: block;</span></span><br><span class="line"><span class="css">            <span class="attribute">margin</span>: <span class="number">0</span> auto;</span></span><br><span class="line"><span class="css">            <span class="attribute">padding</span>: <span class="number">0</span> <span class="number">10px</span>;</span></span><br><span class="line"><span class="css">            <span class="attribute">font-size</span>: <span class="number">14px</span>;</span></span><br><span class="line">        }</span><br><span class="line">        #ul{</span><br><span class="line"><span class="css">            <span class="attribute">width</span>: <span class="number">520px</span>;</span></span><br><span class="line"><span class="css">            <span class="attribute">list-style</span>: none;</span></span><br><span class="line"><span class="css">            <span class="attribute">margin</span>: <span class="number">0</span> auto;</span></span><br><span class="line"><span class="css">            <span class="attribute">padding</span>: <span class="number">0</span>;</span></span><br><span class="line"><span class="css">            <span class="attribute">border</span>:<span class="number">1px</span> solid <span class="number">#ddd</span>;</span></span><br><span class="line"><span class="css">            <span class="attribute">margin-top</span>: -<span class="number">1px</span>;</span></span><br><span class="line"><span class="css">            <span class="attribute">display</span>: none;</span></span><br><span class="line">        }</span><br><span class="line"><span class="css">        <span class="selector-id">#ul</span> <span class="selector-tag">li</span>{</span></span><br><span class="line"><span class="css">            <span class="attribute">line-height</span>: <span class="number">30px</span>;</span></span><br><span class="line"><span class="css">            <span class="attribute">padding</span>: <span class="number">0</span> <span class="number">10px</span>;</span></span><br><span class="line">        }</span><br><span class="line"><span class="css">        <span class="selector-id">#ul</span> <span class="selector-tag">li</span><span class="selector-pseudo">:hover</span>{</span></span><br><span class="line"><span class="css">            <span class="attribute">background-color</span>: <span class="number">#f60</span>;</span></span><br><span class="line"><span class="css">            <span class="attribute">color</span>: <span class="number">#fff</span>;</span></span><br><span class="line">        }</span><br><span class="line">    <span class="tag">&lt;/<span class="name">style</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">script</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="javascript">        <span class="comment">// 2.步骤二</span></span></span><br><span class="line"><span class="javascript">        <span class="comment">// 定义demo函数 (分析接口、数据)</span></span></span><br><span class="line"><span class="javascript">        <span class="function"><span class="keyword">function</span> <span class="title">demo</span>(<span class="params">data</span>)</span>{</span></span><br><span class="line"><span class="javascript">            <span class="keyword">var</span> Ul = <span class="built_in">document</span>.getElementById(<span class="string">'ul'</span>);</span></span><br><span class="line"><span class="javascript">            <span class="keyword">var</span> html = <span class="string">''</span>;</span></span><br><span class="line"><span class="javascript">            <span class="comment">// 如果搜索数据存在 把内容添加进去</span></span></span><br><span class="line">            if (data.s.length) {</span><br><span class="line"><span class="javascript">                <span class="comment">// 隐藏掉的ul显示出来</span></span></span><br><span class="line"><span class="javascript">                Ul.style.display = <span class="string">'block'</span>;</span></span><br><span class="line"><span class="javascript">                <span class="comment">// 搜索到的数据循环追加到li里</span></span></span><br><span class="line"><span class="javascript">                <span class="keyword">for</span>(<span class="keyword">var</span> i = <span class="number">0</span>;i&lt;data.s.length;i++){</span></span><br><span class="line"><span class="javascript">                    html += <span class="string">'&lt;li&gt;'</span>+data.s[i]+<span class="string">'&lt;/li&gt;'</span>;</span></span><br><span class="line">                }</span><br><span class="line"><span class="javascript">                <span class="comment">// 循环的li写入ul</span></span></span><br><span class="line">                Ul.innerHTML = html;</span><br><span class="line">            }</span><br><span class="line">        }</span><br><span class="line"></span><br><span class="line"><span class="javascript">        <span class="comment">// 1.步骤一</span></span></span><br><span class="line"><span class="javascript">        <span class="built_in">window</span>.onload = <span class="function"><span class="keyword">function</span>(<span class="params"></span>)</span>{</span></span><br><span class="line"><span class="javascript">            <span class="comment">// 获取输入框和ul</span></span></span><br><span class="line"><span class="javascript">            <span class="keyword">var</span> Q = <span class="built_in">document</span>.getElementById(<span class="string">'q'</span>);</span></span><br><span class="line"></span><br><span class="line"><span class="javascript">            <span class="comment">// 事件鼠标抬起时候</span></span></span><br><span class="line"><span class="javascript">            Q.onkeyup = <span class="function"><span class="keyword">function</span>(<span class="params"></span>)</span>{</span></span><br><span class="line"><span class="javascript">                <span class="comment">// 如果输入框不等于空</span></span></span><br><span class="line"><span class="javascript">                <span class="keyword">if</span> (<span class="built_in">this</span>.value != <span class="string">''</span>) {</span></span><br><span class="line"><span class="javascript">                    <span class="comment">// ☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆JSONPz重点☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆</span></span></span><br><span class="line"><span class="javascript">                    <span class="comment">// 创建标签</span></span></span><br><span class="line"><span class="javascript">                    <span class="keyword">var</span> script = <span class="built_in">document</span>.createElement(<span class="string">'script'</span>);</span></span><br><span class="line"><span class="javascript">                    <span class="comment">//给定要跨域的地址 赋值给src</span></span></span><br><span class="line"><span class="javascript">                    <span class="comment">//这里是要请求的跨域的地址 我写的是百度搜索的跨域地址</span></span></span><br><span class="line"><span class="javascript">                    <span class="comment">//&amp;cb=demo ---》 会返回 demo(data)</span></span></span><br><span class="line"><span class="javascript">                    script.src = <span class="string">'https://sp0.baidu.com/5a1Fazu8AA54nxGko9WTAnF6hhy/su?wd='</span>+<span class="built_in">this</span>.value+<span class="string">'&amp;cb=demo'</span>;</span></span><br><span class="line"><span class="javascript">                    <span class="comment">// 将组合好的带src的script标签追加到body里</span></span></span><br><span class="line"><span class="javascript">                    <span class="built_in">document</span>.body.appendChild(script);</span></span><br><span class="line">                }</span><br><span class="line">            }</span><br><span class="line">        }</span><br><span class="line">    <span class="tag">&lt;/<span class="name">script</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">head</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;<span class="name">body</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">input</span> <span class="attr">type</span>=<span class="string">"text"</span> <span class="attr">id</span>=<span class="string">"q"</span> /&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">ul</span> <span class="attr">id</span>=<span class="string">"ul"</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">ul</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">body</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">html</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure>]]></content>
      
      
      
    </entry>
    
    
    
    <entry>
      <title></title>
      <link href="/javanblog/2021/04/25/Mybatis/"/>
      <url>/javanblog/2021/04/25/Mybatis/</url>
      
        <content type="html"><![CDATA[<h1 id="MyBatis"><a href="#MyBatis" class="headerlink" title="MyBatis"></a>MyBatis</h1><h2 id="1-MyBatis简介"><a href="#1-MyBatis简介" class="headerlink" title="1 MyBatis简介"></a>1 MyBatis简介</h2><blockquote><p>环境说明</p></blockquote><ul><li>jdk 1.8</li><li>Mysql 5.7.29</li><li>maven 3.6.1</li><li>IDEA</li></ul><blockquote><p>什么是MyBatis</p></blockquote><ul><li>MyBatis是一个基于Java的<strong>持久层框架</strong></li><li>MyBatis 免除了几乎所有的 JDBC 代码以及设置参数和获取结果集的工作</li><li>MyBatis 可以通过简单的 XML 或注解来配置，将接口和 Java 的 实体类 【Plain Old Java Objects,普通的 Java对象】映射成数据库中的记录。</li><li>MyBatis 本是apache的一个开源项目iBatis，, 2010年这个项目由apache 迁移到了google code，并且改名为MyBatis 。</li><li>2013年11月迁移到<strong>GitHub</strong> .</li><li>MyBatis官方文档 : <a href="http://www.mybatis.org/mybatis-3/zh/index.html">http://www.mybatis.org/mybatis-3/zh/index.html</a></li><li>GitHub : <a href="https://github.com/mybatis/mybatis-3">https://github.com/mybatis/mybatis-3</a></li></ul><blockquote><p>什么是持久化</p></blockquote><p><strong>持久化是将程序数据在持久状态和瞬时状态间转换的机制。</strong></p><ul><li>瞬时数据（比如内存中的数据，是不能永久保存的）持久化为持久数据（比如持久化至数据库中，能够长久保存）。</li><li>持久化的主要应用是将内存中的对象存储在数据库中，或者存储在磁盘文件中、XML数据文件中等等。</li><li>JDBC就是一种持久化机制。文件IO也是一种持久化机制。</li></ul><p><strong>为什么需要持久化</strong></p><ul><li>内存断电后数据会丢失</li><li>内存过于昂贵</li></ul><blockquote><p>持久层</p></blockquote><p><strong>什么是持久层</strong></p><ul><li>完成持久化工作的代码块——Dao层。</li><li>数据持久化通常意味着将内存中的数据保存到磁盘上固化，而持久化的实现大多通过各种关系数据库来完成。</li><li>系统架构中，应该有一个相对独立的逻辑层，专注于数据持久化逻辑的实现。</li></ul><blockquote><p>为什么需要Mybatis</p></blockquote><ul><li><p>Mybatis帮助程序员将数据存入数据库中，和从数据库中获取数据。</p></li><li><p>传统的JDBC操作，存在重复代码块，开发效率低，使用MyBatis可以<strong>提高开发效率</strong>。</p></li><li><p>MyBatis 是一个半自动化的<strong>ORM框架 (Object Relationship Mapping) ——&gt;对象关系映射</strong></p></li><li><p>MyBatis的优点</p><ul><li>简单易学：安装及配置简单，能够通过阅读文档和源代码掌握它的设计思想及实现。</li><li>使用灵活：SQL语句写在xml配置文件中，便于统一管理和优化。</li><li>解除耦合：SQL语句与程序代码分离，提高可维护性。</li><li>支持动态编写SQL</li><li>……</li></ul></li></ul><h2 id="2-MyBatis第一个程序"><a href="#2-MyBatis第一个程序" class="headerlink" title="2 MyBatis第一个程序"></a>2 MyBatis第一个程序</h2><p><strong>思路流程：搭建环境—&gt;导入MyBatis—&gt;编写代码—&gt;测试</strong></p><p><strong>该程序实现CRUD操作，项目完整结构图及常见问题在后文说明。</strong></p><blockquote><p>代码演示</p></blockquote><p>1、 搭建实验所需数据库</p><figure class="highlight sql"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">CREATE</span> DATABASE `mybatis`;</span><br><span class="line"></span><br><span class="line">USE `mybatis`;</span><br><span class="line"># 如果表格存在，则删除</span><br><span class="line"><span class="keyword">DROP</span> <span class="keyword">TABLE</span> IF <span class="keyword">EXISTS</span> `<span class="keyword">user</span>`;</span><br><span class="line"></span><br><span class="line"><span class="keyword">CREATE</span> <span class="keyword">TABLE</span> `<span class="keyword">user</span>` (</span><br><span class="line">`id` <span class="type">int</span>(<span class="number">20</span>) <span class="keyword">NOT</span> <span class="keyword">NULL</span>,</span><br><span class="line">`name` <span class="type">varchar</span>(<span class="number">30</span>) <span class="keyword">DEFAULT</span> <span class="keyword">NULL</span>,</span><br><span class="line">`pwd` <span class="type">varchar</span>(<span class="number">30</span>) <span class="keyword">DEFAULT</span> <span class="keyword">NULL</span>,</span><br><span class="line"><span class="keyword">PRIMARY</span> KEY (`id`)</span><br><span class="line">) ENGINE<span class="operator">=</span>InnoDB <span class="keyword">DEFAULT</span> CHARSET<span class="operator">=</span>utf8;</span><br><span class="line"></span><br><span class="line"><span class="keyword">insert</span>  <span class="keyword">into</span> `<span class="keyword">user</span>`(`id`,`name`,`pwd`) <span class="keyword">values</span> (<span class="number">1</span>,<span class="string">'BG'</span>,<span class="string">'123456'</span>),(<span class="number">2</span>,<span class="string">'张三'</span>,<span class="string">'abcdef'</span>),(<span class="number">3</span>,<span class="string">'李四'</span>,<span class="string">'987654'</span>),(<span class="number">4</span>,<span class="string">'王五'</span>,<span class="string">'123444'</span>);</span><br></pre></td></tr></tbody></table></figure><p>2、IDEA创建项目</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201126112906566.png" alt="image-20201126112906566"></p><p>选择Maven项目，选择JDK版本，然后点击Next。</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201126113256584.png" alt="image-20201126113256584"></p><p>设置项目名称，及GroupId（一般为公司域名），然后点击Finish，完成项目创建。</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201126113436936.png" alt="image-20201126113436936"></p><p>完成项目创建后的结构图，删除掉src文件夹，将该目录作为父工程，此pom.xml为父工程所有，可供所有子模块使用。</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201126114811520.png" alt="image-20201126114811520"></p><p>右键当前项目，创建新模块。</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201126114903827.png" alt="image-20201126114903827"></p><p>输入子模块名称，点击Finish，即完成模块创建。</p><p>3、导入相关jar包</p><ul><li>在父工程的pom.xml文件中导入相关jar包，在<a href="https://mvnrepository.com/">Maven</a>仓库中查找</li></ul><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">dependencies</span>&gt;</span></span><br><span class="line">    <span class="comment">&lt;!--mysql驱动--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>mysql<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>mysql-connector-java<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">version</span>&gt;</span>5.1.48<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>org.mybatis<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>mybatis<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">version</span>&gt;</span>3.5.2<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--用于测试--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>junit<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>junit<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">version</span>&gt;</span>4.12<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">dependencies</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>4、编写MyBatis核心配置文件</p><ul><li>查看帮助文档，即Mybatis官方文档</li></ul><p><strong>mybatis-config.xml</strong></p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8" ?&gt;</span></span><br><span class="line"><span class="meta">&lt;!DOCTYPE <span class="meta-keyword">configuration</span></span></span><br><span class="line"><span class="meta">        <span class="meta-keyword">PUBLIC</span> <span class="meta-string">"-//mybatis.org//DTD Config 3.0//EN"</span></span></span><br><span class="line"><span class="meta">        <span class="meta-string">"http://mybatis.org/dtd/mybatis-3-config.dtd"</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">configuration</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">environments</span> <span class="attr">default</span>=<span class="string">"development"</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">environment</span> <span class="attr">id</span>=<span class="string">"development"</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">transactionManager</span> <span class="attr">type</span>=<span class="string">"JDBC"</span>/&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">dataSource</span> <span class="attr">type</span>=<span class="string">"POOLED"</span>&gt;</span></span><br><span class="line">                <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"driver"</span> <span class="attr">value</span>=<span class="string">"com.mysql.jdbc.Driver"</span>/&gt;</span></span><br><span class="line">                <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"url"</span> <span class="attr">value</span>=<span class="string">"jdbc:mysql://localhost:3306/mybatis?Unicode=true<span class="symbol">&amp;amp;</span>characterEncoding=utf8"</span>/&gt;</span></span><br><span class="line">                <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"username"</span> <span class="attr">value</span>=<span class="string">"root"</span>/&gt;</span></span><br><span class="line">                <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"password"</span> <span class="attr">value</span>=<span class="string">"1234"</span>/&gt;</span></span><br><span class="line">            <span class="tag">&lt;/<span class="name">dataSource</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">environment</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">environments</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--编写玩Mapper接口及对应的XML配置文件后，需要在MyBatis核心配置文件中注册，以下两种格式都可以--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">mappers</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">mapper</span> <span class="attr">class</span>=<span class="string">"com.bg.mapper.UserMapper"</span>/&gt;</span></span><br><span class="line"><span class="comment">&lt;!--&lt;mapper resource="com/bg/mapper/UserMapper.xml"/&gt;--&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">mappers</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">configuration</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>5、编写MyBatis工具类</p><ul><li>查看帮助文档</li></ul><p><strong>MyBatisTool.java</strong></p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.bg.tools;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> org.apache.ibatis.io.Resources;</span><br><span class="line"><span class="keyword">import</span> org.apache.ibatis.session.SqlSession;</span><br><span class="line"><span class="keyword">import</span> org.apache.ibatis.session.SqlSessionFactory;</span><br><span class="line"><span class="keyword">import</span> org.apache.ibatis.session.SqlSessionFactoryBuilder;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> java.io.IOException;</span><br><span class="line"><span class="keyword">import</span> java.io.InputStream;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">MyBatisTool</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> InputStream inputStream;</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> SqlSessionFactory sqlSessionFactory;</span><br><span class="line">    <span class="keyword">static</span>{</span><br><span class="line"></span><br><span class="line">        <span class="keyword">try</span> {</span><br><span class="line">            String resource = <span class="string">"mybatis-config.xml"</span>;</span><br><span class="line">            <span class="comment">// 加载MyBatis核心配置文件</span></span><br><span class="line">            inputStream = Resources.getResourceAsStream(resource);</span><br><span class="line">            <span class="comment">// 通过输入流构建SqlSessionFactory</span></span><br><span class="line">            sqlSessionFactory = <span class="keyword">new</span> SqlSessionFactoryBuilder().build(inputStream);</span><br><span class="line">        } <span class="keyword">catch</span> (IOException e) {</span><br><span class="line">            e.printStackTrace();</span><br><span class="line">        }<span class="keyword">finally</span> {</span><br><span class="line">            <span class="comment">// 关闭输入流</span></span><br><span class="line">            <span class="keyword">if</span>(inputStream == <span class="keyword">null</span>){</span><br><span class="line">                <span class="keyword">try</span> {</span><br><span class="line">                    inputStream.close();</span><br><span class="line">                } <span class="keyword">catch</span> (IOException e) {</span><br><span class="line">                    e.printStackTrace();</span><br><span class="line">                }</span><br><span class="line">            }</span><br><span class="line">        }</span><br><span class="line"></span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 获取SqlSession实例，用来操作数据库</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> SqlSession <span class="title">getSqlSession</span><span class="params">()</span></span>{</span><br><span class="line">        <span class="keyword">return</span> sqlSessionFactory.openSession();</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">}</span><br><span class="line"></span><br></pre></td></tr></tbody></table></figure><p>6、创建实体类</p><p><strong>User.java</strong></p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.bg.pojo;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">User</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">int</span> id;</span><br><span class="line">    <span class="keyword">private</span> String name;</span><br><span class="line">    <span class="keyword">private</span> String pwd;</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="title">User</span><span class="params">()</span> </span>{</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="title">User</span><span class="params">(<span class="keyword">int</span> id, String name, String pwd)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.id = id;</span><br><span class="line">        <span class="keyword">this</span>.name = name;</span><br><span class="line">        <span class="keyword">this</span>.pwd = pwd;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">getId</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> id;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setId</span><span class="params">(<span class="keyword">int</span> id)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.id = id;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">getName</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> name;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setName</span><span class="params">(String name)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.name = name;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">getPwd</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> pwd;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setPwd</span><span class="params">(String pwd)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.pwd = pwd;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">toString</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> <span class="string">"User{"</span> +</span><br><span class="line">                <span class="string">"id="</span> + id +</span><br><span class="line">                <span class="string">", name='"</span> + name + <span class="string">'\''</span> +</span><br><span class="line">                <span class="string">", pwd='"</span> + pwd + <span class="string">'\''</span> +</span><br><span class="line">                <span class="string">'}'</span>;</span><br><span class="line">    }</span><br><span class="line">}</span><br><span class="line"></span><br></pre></td></tr></tbody></table></figure><p>7、编写Mapper接口类</p><p><strong>UserMapper.java</strong></p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.bg.mapper;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> com.bg.pojo.User;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> java.util.List;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">UserMapper</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 查询表格中的所有用户</span></span><br><span class="line">    <span class="function">List&lt;User&gt; <span class="title">getUserList</span><span class="params">()</span></span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 根据Id查询用户</span></span><br><span class="line">    <span class="function">User <span class="title">getUserById</span><span class="params">(<span class="keyword">int</span> userId)</span></span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 增加一个用户</span></span><br><span class="line">    <span class="function"><span class="keyword">int</span> <span class="title">addUser</span><span class="params">(User user)</span></span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 修改一个用户</span></span><br><span class="line">    <span class="function"><span class="keyword">int</span> <span class="title">updateUser</span><span class="params">(User user)</span></span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 删除一个用户</span></span><br><span class="line">    <span class="function"><span class="keyword">int</span> <span class="title">deleteUser</span><span class="params">(<span class="keyword">int</span> userId)</span></span>;</span><br><span class="line">}</span><br><span class="line"></span><br></pre></td></tr></tbody></table></figure><p>8、编写Mapper.xml配置文件</p><p><strong>UserMapper.xml</strong></p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8" ?&gt;</span></span><br><span class="line"><span class="meta">&lt;!DOCTYPE <span class="meta-keyword">mapper</span></span></span><br><span class="line"><span class="meta">        <span class="meta-keyword">PUBLIC</span> <span class="meta-string">"-//mybatis.org//DTD Mapper 3.0//EN"</span></span></span><br><span class="line"><span class="meta">        <span class="meta-string">"http://mybatis.org/dtd/mybatis-3-mapper.dtd"</span>&gt;</span></span><br><span class="line"><span class="comment">&lt;!--绑定接口--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">mapper</span> <span class="attr">namespace</span>=<span class="string">"com.bg.mapper.UserMapper"</span>&gt;</span></span><br><span class="line">    <span class="comment">&lt;!--绑定函数和返回对象类型--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getUserList"</span> <span class="attr">resultType</span>=<span class="string">"com.bg.pojo.User"</span>&gt;</span></span><br><span class="line">        SELECT * FROM user</span><br><span class="line">    <span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getUserById"</span> <span class="attr">resultType</span>=<span class="string">"com.bg.pojo.User"</span>&gt;</span></span><br><span class="line">        SELECT * FROM user WHERE id = #{userId}</span><br><span class="line">    <span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--返回类型为基本类型，可以省略--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">insert</span> <span class="attr">id</span>=<span class="string">"addUser"</span> <span class="attr">parameterType</span>=<span class="string">"com.bg.pojo.User"</span>&gt;</span></span><br><span class="line">        INSERT INTO user(id, name, pwd) VALUES (#{id}, #{name}, #{pwd})</span><br><span class="line">    <span class="tag">&lt;/<span class="name">insert</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">update</span> <span class="attr">id</span>=<span class="string">"updateUser"</span> <span class="attr">parameterType</span>=<span class="string">"com.bg.pojo.User"</span>&gt;</span></span><br><span class="line">        UPDATE user SET name = #{name}, pwd = #{pwd} WHERE id = #{id}</span><br><span class="line">    <span class="tag">&lt;/<span class="name">update</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--输入参数为基本数据类型，也可以省略不写--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">delete</span> <span class="attr">id</span>=<span class="string">"deleteUser"</span> <span class="attr">parameterType</span>=<span class="string">"int"</span>&gt;</span></span><br><span class="line">        DELETE FROM user WHERE id = #{userId};</span><br><span class="line">    <span class="tag">&lt;/<span class="name">delete</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">mapper</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>9、编写测试类</p><ul><li>Junit包测试</li></ul><p>MyTest.java</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br><span class="line">106</span><br><span class="line">107</span><br><span class="line">108</span><br><span class="line">109</span><br><span class="line">110</span><br><span class="line">111</span><br><span class="line">112</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span> com.bg.mapper.UserMapper;</span><br><span class="line"><span class="keyword">import</span> com.bg.pojo.User;</span><br><span class="line"><span class="keyword">import</span> com.bg.tools.MyBatisTool;</span><br><span class="line"><span class="keyword">import</span> org.apache.ibatis.session.SqlSession;</span><br><span class="line"><span class="keyword">import</span> org.junit.Test;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> java.util.List;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">MyTest</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 使用junit进行测试，需要添加该注解</span></span><br><span class="line">    <span class="meta">@Test</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">getUserList</span><span class="params">()</span></span>{</span><br><span class="line">        <span class="comment">// 首先获得SqlSession对象</span></span><br><span class="line">        SqlSession sqlSession = MyBatisTool.getSqlSession();</span><br><span class="line">        <span class="comment">// 通过SqlSession对象获取Mapper接口对象</span></span><br><span class="line">        UserMapper mapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line">        <span class="comment">// 调用mapper中的函数，执行sql</span></span><br><span class="line">        List&lt;User&gt; userList = mapper.getUserList();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 遍历结果集，并输出</span></span><br><span class="line">        <span class="keyword">for</span> (User user : userList) {</span><br><span class="line">            System.out.println(user.toString());</span><br><span class="line">        }</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 使用完毕后，关闭SqlSession对象</span></span><br><span class="line">        sqlSession.close();</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Test</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">getUserById</span><span class="params">()</span></span>{</span><br><span class="line">        <span class="comment">// 首先获得SqlSession对象</span></span><br><span class="line">        SqlSession sqlSession = MyBatisTool.getSqlSession();</span><br><span class="line">        <span class="comment">// 通过SqlSession对象获取Mapper接口对象</span></span><br><span class="line">        UserMapper mapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line">        <span class="comment">// 调用mapper中的函数，执行sql</span></span><br><span class="line">        User user = mapper.getUserById(<span class="number">3</span>);</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 遍历结果，并输出</span></span><br><span class="line">        System.out.println(user.toString());</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">        <span class="comment">// 使用完毕后，关闭SqlSession对象</span></span><br><span class="line">        sqlSession.close();</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Test</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">addUser</span><span class="params">()</span></span>{</span><br><span class="line">        <span class="comment">// 首先获得SqlSession对象</span></span><br><span class="line">        SqlSession sqlSession = MyBatisTool.getSqlSession();</span><br><span class="line">        <span class="comment">// 通过SqlSession对象获取Mapper接口对象</span></span><br><span class="line">        UserMapper mapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line">        <span class="comment">// 调用mapper中的函数，执行sql</span></span><br><span class="line">        User user = <span class="keyword">new</span> User(<span class="number">5</span>, <span class="string">"赵六"</span>, <span class="string">"9527"</span>);</span><br><span class="line"></span><br><span class="line">        <span class="keyword">int</span> i = mapper.addUser(user);</span><br><span class="line">        <span class="keyword">if</span>(i == <span class="number">1</span>){</span><br><span class="line">            System.out.println(<span class="string">"插入数据成功"</span>);</span><br><span class="line">            <span class="comment">// 因为SqlSession默认关闭事务自动提交，因此插入数据成功后，我们需要手动提交事务，才能在数据库中完成插入</span></span><br><span class="line">            sqlSession.commit();</span><br><span class="line">        }<span class="keyword">else</span>{</span><br><span class="line">            System.out.println(<span class="string">"插入数据失败"</span>);</span><br><span class="line">        }</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 使用完毕后，关闭SqlSession对象</span></span><br><span class="line">        sqlSession.close();</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Test</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">updateUser</span><span class="params">()</span></span>{</span><br><span class="line">        <span class="comment">// 首先获得SqlSession对象</span></span><br><span class="line">        SqlSession sqlSession = MyBatisTool.getSqlSession();</span><br><span class="line">        <span class="comment">// 通过SqlSession对象获取Mapper接口对象</span></span><br><span class="line">        UserMapper mapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line">        <span class="comment">// 调用mapper中的函数，执行sql</span></span><br><span class="line">        User user = <span class="keyword">new</span> User(<span class="number">3</span>, <span class="string">"张飞"</span>, <span class="string">"00222555"</span>);</span><br><span class="line"></span><br><span class="line">        <span class="keyword">int</span> i = mapper.updateUser(user);</span><br><span class="line">        <span class="keyword">if</span>(i == <span class="number">1</span>){</span><br><span class="line">            System.out.println(<span class="string">"更新数据成功"</span>);</span><br><span class="line">            <span class="comment">// 因为SqlSession默认关闭事务自动提交，因此更新数据成功后，我们需要手动提交事务，才能在数据库中完成插入</span></span><br><span class="line">            sqlSession.commit();</span><br><span class="line">        }<span class="keyword">else</span>{</span><br><span class="line">            System.out.println(<span class="string">"更新数据失败"</span>);</span><br><span class="line">        }</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 使用完毕后，关闭SqlSession对象</span></span><br><span class="line">        sqlSession.close();</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Test</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">deleteUser</span><span class="params">()</span></span>{</span><br><span class="line">        <span class="comment">// 首先获得SqlSession对象</span></span><br><span class="line">        SqlSession sqlSession = MyBatisTool.getSqlSession();</span><br><span class="line">        <span class="comment">// 通过SqlSession对象获取Mapper接口对象</span></span><br><span class="line">        UserMapper mapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line">        <span class="comment">// 调用mapper中的函数，执行sql</span></span><br><span class="line"></span><br><span class="line">        <span class="keyword">int</span> i = mapper.deleteUser(<span class="number">2</span>);</span><br><span class="line">        <span class="keyword">if</span>(i == <span class="number">1</span>){</span><br><span class="line">            System.out.println(<span class="string">"删除数据成功"</span>);</span><br><span class="line">            <span class="comment">// 因为SqlSession默认关闭事务自动提交，因此删除数据成功后，我们需要手动提交事务，才能在数据库中完成插入</span></span><br><span class="line">            sqlSession.commit();</span><br><span class="line">        }<span class="keyword">else</span>{</span><br><span class="line">            System.out.println(<span class="string">"删除数据失败"</span>);</span><br><span class="line">        }</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 使用完毕后，关闭SqlSession对象</span></span><br><span class="line">        sqlSession.close();</span><br><span class="line">    }</span><br><span class="line">}</span><br><span class="line"></span><br></pre></td></tr></tbody></table></figure><p>10、运行测试，成功查询数据</p><blockquote><p>项目完整结构图</p></blockquote><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201126152933310.png" alt="image-20201126152933310"></p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201126152951513.png" alt="image-20201126152951513"></p><blockquote><p>问题说明</p></blockquote><p><strong>Maven静态资源过滤问题</strong></p><p>通常编译maven项目时，只能过滤resources下面的配置文件，当我们把配置文件写到java文件夹下面时，需要在pom.xml中，显示的开启资源过滤，使java文件夹下的配置文件能够被读取并编译。</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!--在build中配置resource，来防止我们资源导出失败的问题，true代表允许过滤--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">build</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">resources</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">resource</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">directory</span>&gt;</span>src/main/resources<span class="tag">&lt;/<span class="name">directory</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">includes</span>&gt;</span></span><br><span class="line">                <span class="tag">&lt;<span class="name">include</span>&gt;</span>**/*.properties<span class="tag">&lt;/<span class="name">include</span>&gt;</span></span><br><span class="line">                <span class="tag">&lt;<span class="name">include</span>&gt;</span>**/*.xml<span class="tag">&lt;/<span class="name">include</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;/<span class="name">includes</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">filtering</span>&gt;</span>true<span class="tag">&lt;/<span class="name">filtering</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">resource</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">resource</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">directory</span>&gt;</span>src/main/java<span class="tag">&lt;/<span class="name">directory</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">includes</span>&gt;</span></span><br><span class="line">                <span class="tag">&lt;<span class="name">include</span>&gt;</span>**/*.properties<span class="tag">&lt;/<span class="name">include</span>&gt;</span></span><br><span class="line">                <span class="tag">&lt;<span class="name">include</span>&gt;</span>**/*.xml<span class="tag">&lt;/<span class="name">include</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;/<span class="name">includes</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">filtering</span>&gt;</span>true<span class="tag">&lt;/<span class="name">filtering</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">resource</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">resources</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">build</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p><strong>配置文件中文注释问题</strong></p><p>因为在配置文件中添加了中文注释，会导致乱码，故会报错。</p><figure class="highlight"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">### Cause: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: org.apache.ibatis.builder.BuilderException: Error creating document instance.  Cause: com.sun.org.apache.xerces.internal.impl.io.MalformedByteSequenceException: 1 字节的 UTF-8 序列的字节 1 无效。</span><br></pre></td></tr></tbody></table></figure><p>为了解决该问题，需要在父类的pom.xml中配置项目编码。</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">properties</span>&gt;</span></span><br><span class="line">      <span class="tag">&lt;<span class="name">project.build.sourceEncoding</span>&gt;</span>UTF8<span class="tag">&lt;/<span class="name">project.build.sourceEncoding</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">properties</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>在父类中pom.xml中添加的所有配置信息，在所有子模块中均生效。</p><h2 id="3-CRUD详解"><a href="#3-CRUD详解" class="headerlink" title="3 CRUD详解"></a>3 CRUD详解</h2><p><strong>namespace中的包名要和 Dao/mapper接口的包名一致！</strong></p><p><strong>UserMapper.xml</strong></p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8" ?&gt;</span></span><br><span class="line"><span class="meta">&lt;!DOCTYPE <span class="meta-keyword">mapper</span></span></span><br><span class="line"><span class="meta">        <span class="meta-keyword">PUBLIC</span> <span class="meta-string">"-//mybatis.org//DTD Mapper 3.0//EN"</span></span></span><br><span class="line"><span class="meta">        <span class="meta-string">"http://mybatis.org/dtd/mybatis-3-mapper.dtd"</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;<span class="name">mapper</span> <span class="attr">namespace</span>=<span class="string">"com.zzb.dao.UserMapper"</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getUserList"</span> <span class="attr">resultType</span>=<span class="string">"com.zzb.pojo.User"</span>&gt;</span></span><br><span class="line">      select * from user</span><br><span class="line">    <span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getUserListByLike"</span> <span class="attr">parameterType</span>=<span class="string">"String"</span> <span class="attr">resultType</span>=<span class="string">"com.zzb.pojo.User"</span>&gt;</span></span><br><span class="line">      select * from user where name like #{value}</span><br><span class="line">    <span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br><span class="line"></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getUserById"</span> <span class="attr">parameterType</span>=<span class="string">"int"</span> <span class="attr">resultType</span>=<span class="string">"com.zzb.pojo.User"</span>&gt;</span></span><br><span class="line">        select * from user where id = #{id}</span><br><span class="line">    <span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getUserById2"</span> <span class="attr">parameterType</span>=<span class="string">"map"</span> <span class="attr">resultType</span>=<span class="string">"com.zzb.pojo.User"</span>&gt;</span></span><br><span class="line">        select * from user where id = #{keyId}</span><br><span class="line">    <span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--对象的属性可以直接取出来--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">insert</span> <span class="attr">id</span>=<span class="string">"addUser"</span> <span class="attr">parameterType</span>=<span class="string">"com.zzb.pojo.User"</span>&gt;</span></span><br><span class="line">        insert into user (id, name, pwd) values ( #{id}, #{name}, #{pwd});</span><br><span class="line">    <span class="tag">&lt;/<span class="name">insert</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">update</span> <span class="attr">id</span>=<span class="string">"updateUser"</span> <span class="attr">parameterType</span>=<span class="string">"com.zzb.pojo.User"</span>&gt;</span></span><br><span class="line">        update  user set name = #{name}, pwd = #{pwd} where id = #{id};</span><br><span class="line">    <span class="tag">&lt;/<span class="name">update</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><blockquote><p>namespace</p></blockquote><p>配置文件中的namespace中的名称为对应的Mapper接口的完整包名，必须一致！</p><blockquote><p>select</p></blockquote><ul><li>select标签是mybatis中最常用的标签之一</li><li>select语句中有很多属性<ul><li>parameterType：传入SQL语句的参数类型，如果是基本类型可以省略，也可以通过Map进行参数传递</li><li>resultType：SQL语句的返回值类型，如果是基本类型可以省略，其他对象必须为完整的类名（含包名）或者别名</li><li>接口中的方法名与XML映射文件中的SQL语句ID要一一对应</li><li>resultMap：为返回结果集映射，即实体类中的属性与数据库表中的表头名称无法一一对应时，需要进行结果集的映射，才能保证成功完整的取出数据。</li></ul></li></ul><p><strong>根据id查询用户</strong></p><p>1、在UserMapper接口中添加相应的方法</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 根据Id查询用户</span></span><br><span class="line"><span class="function">User <span class="title">getUserById</span><span class="params">(<span class="keyword">int</span> userId)</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>2、在UserMapper.xml中添加select语句</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getUserById"</span> <span class="attr">resultType</span>=<span class="string">"com.bg.pojo.User"</span>&gt;</span></span><br><span class="line">    SELECT * FROM user WHERE id = #{userId}</span><br><span class="line"><span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p><strong>参数类型传递方法</strong></p><ul><li><p>直接传递参数，可以按照上述代码传递参数，也可以在接口方法的参数前添加@Param属性，显示的指定参数名。</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span> org.apache.ibatis.annotations.Param;    </span><br><span class="line"></span><br><span class="line"><span class="comment">// 根据Id查询用户</span></span><br><span class="line">    <span class="function">User <span class="title">getUserById</span><span class="params">(<span class="meta">@Param("id")</span> <span class="keyword">int</span> userId)</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>那么在XML配置文件中，就要做相应的修改（userId —&gt; id）</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getUserById"</span> <span class="attr">resultType</span>=<span class="string">"com.bg.pojo.User"</span>&gt;</span></span><br><span class="line">    SELECT * FROM user WHERE id = #{id}</span><br><span class="line"><span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure></li><li><p>使用万能的Map传递参数，将需要传递的参数封装程Map，将接口修改为如下所示。</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span> java.util.Map;    </span><br><span class="line"></span><br><span class="line"><span class="comment">// 根据Id查询用户</span></span><br><span class="line">    <span class="function">User <span class="title">getUserById</span><span class="params">(Map&lt;String, Object&gt; map)</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>XML配置文件无需修改，也可以显示的指明传入参数类型为map</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getUserById"</span> <span class="attr">parameterType</span>=<span class="string">"map"</span> <span class="attr">resultType</span>=<span class="string">"com.bg.pojo.User"</span>&gt;</span></span><br><span class="line">    SELECT * FROM user WHERE id = #{id}</span><br><span class="line"><span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>测试时，需要将传入参数设置为Map类型：</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">getUserById</span><span class="params">()</span></span>{</span><br><span class="line">    <span class="comment">// 首先获得SqlSession对象</span></span><br><span class="line">    SqlSession sqlSession = MyBatisTool.getSqlSession();</span><br><span class="line">    <span class="comment">// 通过SqlSession对象获取Mapper接口对象</span></span><br><span class="line">    UserMapper mapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line">    <span class="comment">// map封装参数</span></span><br><span class="line">    Map&lt;String, Object&gt; map = <span class="keyword">new</span> HashMap&lt;String, Object&gt;();</span><br><span class="line">    map.put(<span class="string">"id"</span>, <span class="number">3</span>);</span><br><span class="line">    <span class="comment">// 调用mapper中的函数，执行sql</span></span><br><span class="line">    User user = mapper.getUserById(map);</span><br><span class="line">  </span><br><span class="line">    <span class="comment">// 遍历结果，并输出</span></span><br><span class="line">    System.out.println(user.toString());</span><br><span class="line">  </span><br><span class="line">  </span><br><span class="line">    <span class="comment">// 使用完毕后，关闭SqlSession对象</span></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure></li></ul><blockquote><p>insert</p></blockquote><p><strong>给数据库增加一个用户</strong></p><p>1、在UserMapper接口中添加对应的方法</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 增加一个用户</span></span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">addUser</span><span class="params">(User user)</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>2、在UserMapper.xml中添加insert语句</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!--返回类型为基本类型，可以省略--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">insert</span> <span class="attr">id</span>=<span class="string">"addUser"</span> <span class="attr">parameterType</span>=<span class="string">"com.bg.pojo.User"</span>&gt;</span></span><br><span class="line">    INSERT INTO user(id, name, pwd) VALUES (#{id}, #{name}, #{pwd})</span><br><span class="line"><span class="tag">&lt;/<span class="name">insert</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>注意：参数直接去User对象中对应的属性即可。</p><p>3、测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">addUser</span><span class="params">()</span></span>{</span><br><span class="line">    <span class="comment">// 首先获得SqlSession对象</span></span><br><span class="line">    SqlSession sqlSession = MyBatisTool.getSqlSession();</span><br><span class="line">    <span class="comment">// 通过SqlSession对象获取Mapper接口对象</span></span><br><span class="line">    UserMapper mapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line">    <span class="comment">// 调用mapper中的函数，执行sql</span></span><br><span class="line">    User user = <span class="keyword">new</span> User(<span class="number">5</span>, <span class="string">"赵六"</span>, <span class="string">"9527"</span>);</span><br><span class="line"></span><br><span class="line">    <span class="keyword">int</span> i = mapper.addUser(user);</span><br><span class="line">    <span class="keyword">if</span>(i == <span class="number">1</span>){</span><br><span class="line">        System.out.println(<span class="string">"插入数据成功"</span>);</span><br><span class="line">        <span class="comment">// 因为SqlSession默认关闭事务自动提交，因此插入数据成功后，我们需要手动提交事务，才能在数据库中完成插入</span></span><br><span class="line">        sqlSession.commit();</span><br><span class="line">    }<span class="keyword">else</span>{</span><br><span class="line">        System.out.println(<span class="string">"插入数据失败"</span>);</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 使用完毕后，关闭SqlSession对象</span></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><strong>注意：增、删、改操作都需要提交事务</strong></p><blockquote><p>update</p></blockquote><p>通常使用update标签进行更新数据的操作。</p><p><strong>修改用户信息</strong></p><p>1、在UserMapper接口中添加对应的方法</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 修改一个用户</span></span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">updateUser</span><span class="params">(User user)</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>2、在UserMapper.xml中添加insert语句</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">update</span> <span class="attr">id</span>=<span class="string">"updateUser"</span> <span class="attr">parameterType</span>=<span class="string">"com.bg.pojo.User"</span>&gt;</span></span><br><span class="line">    UPDATE user SET name = #{name}, pwd = #{pwd} WHERE id = #{id}</span><br><span class="line"><span class="tag">&lt;/<span class="name">update</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>3、测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">updateUser</span><span class="params">()</span></span>{</span><br><span class="line">    <span class="comment">// 首先获得SqlSession对象</span></span><br><span class="line">    SqlSession sqlSession = MyBatisTool.getSqlSession();</span><br><span class="line">    <span class="comment">// 通过SqlSession对象获取Mapper接口对象</span></span><br><span class="line">    UserMapper mapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line">    <span class="comment">// 调用mapper中的函数，执行sql</span></span><br><span class="line">    User user = <span class="keyword">new</span> User(<span class="number">3</span>, <span class="string">"张飞"</span>, <span class="string">"00222555"</span>);</span><br><span class="line"></span><br><span class="line">    <span class="keyword">int</span> i = mapper.updateUser(user);</span><br><span class="line">    <span class="keyword">if</span>(i == <span class="number">1</span>){</span><br><span class="line">        System.out.println(<span class="string">"更新数据成功"</span>);</span><br><span class="line">        <span class="comment">// 因为SqlSession默认关闭事务自动提交，因此更新数据成功后，我们需要手动提交事务，才能在数据库中完成插入</span></span><br><span class="line">        sqlSession.commit();</span><br><span class="line">    }<span class="keyword">else</span>{</span><br><span class="line">        System.out.println(<span class="string">"更新数据失败"</span>);</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 使用完毕后，关闭SqlSession对象</span></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><blockquote><p>delete</p></blockquote><p><strong>根据id删除一个用户</strong></p><p>1、在UserMapper接口中添加对应的方法</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 删除一个用户</span></span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">deleteUser</span><span class="params">(<span class="keyword">int</span> userId)</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>2、在UserMapper.xml中添加insert语句</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!--输入参数为基本数据类型，也可以省略不写--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">delete</span> <span class="attr">id</span>=<span class="string">"deleteUser"</span> <span class="attr">parameterType</span>=<span class="string">"int"</span>&gt;</span></span><br><span class="line">    DELETE FROM user WHERE id = #{userId};</span><br><span class="line"><span class="tag">&lt;/<span class="name">delete</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>3、测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">deleteUser</span><span class="params">()</span></span>{</span><br><span class="line">    <span class="comment">// 首先获得SqlSession对象</span></span><br><span class="line">    SqlSession sqlSession = MyBatisTool.getSqlSession();</span><br><span class="line">    <span class="comment">// 通过SqlSession对象获取Mapper接口对象</span></span><br><span class="line">    UserMapper mapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line">    <span class="comment">// 调用mapper中的函数，执行sql</span></span><br><span class="line"></span><br><span class="line">    <span class="keyword">int</span> i = mapper.deleteUser(<span class="number">2</span>);</span><br><span class="line">    <span class="keyword">if</span>(i == <span class="number">1</span>){</span><br><span class="line">        System.out.println(<span class="string">"删除数据成功"</span>);</span><br><span class="line">        <span class="comment">// 因为SqlSession默认关闭事务自动提交，因此删除数据成功后，我们需要手动提交事务，才能在数据库中完成插入</span></span><br><span class="line">        sqlSession.commit();</span><br><span class="line">    }<span class="keyword">else</span>{</span><br><span class="line">        System.out.println(<span class="string">"删除数据失败"</span>);</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 使用完毕后，关闭SqlSession对象</span></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><strong>模糊查询</strong></p><p>在UserMapper接口中添加对应的方法</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 模糊查询</span></span><br><span class="line"><span class="function">User <span class="title">getUserByLike</span><span class="params">(String s)</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>方法1：java代码中添加sql通配符</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!--模糊查询--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getUserByLike"</span> <span class="attr">resultType</span>=<span class="string">"com.bg.pojo.User"</span>&gt;</span></span><br><span class="line">    SELECT * FROM user WHERE name LIKE #{s}</span><br><span class="line"><span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">getUserByLike</span><span class="params">()</span></span>{</span><br><span class="line">    <span class="comment">// 首先获得SqlSession对象</span></span><br><span class="line">    SqlSession sqlSession = MyBatisTool.getSqlSession();</span><br><span class="line">    <span class="comment">// 通过SqlSession对象获取Mapper接口对象</span></span><br><span class="line">    UserMapper mapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line">    <span class="comment">// 调用mapper中的函数，执行sql</span></span><br><span class="line">    User user = mapper.getUserByLike(<span class="string">"%张%"</span>);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 遍历结果，并输出</span></span><br><span class="line">    System.out.println(user.toString());</span><br><span class="line">    </span><br><span class="line">    <span class="comment">// 使用完毕后，关闭SqlSession对象</span></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>方法2：在sql语句中拼接通配符</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!--模糊查询--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getUserByLike"</span> <span class="attr">resultType</span>=<span class="string">"com.bg.pojo.User"</span>&gt;</span></span><br><span class="line">    SELECT * FROM user WHERE name LIKE "%"#{s}"%"  //这里写死了，是为了防止sql注入</span><br><span class="line"><span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">getUserByLike</span><span class="params">()</span></span>{</span><br><span class="line">    <span class="comment">// 首先获得SqlSession对象</span></span><br><span class="line">    SqlSession sqlSession = MyBatisTool.getSqlSession();</span><br><span class="line">    <span class="comment">// 通过SqlSession对象获取Mapper接口对象</span></span><br><span class="line">    UserMapper mapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line">    <span class="comment">// 调用mapper中的函数，执行sql</span></span><br><span class="line">    User user = mapper.getUserByLike(<span class="string">"王"</span>);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 遍历结果，并输出</span></span><br><span class="line">    System.out.println(user.toString());</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 使用完毕后，关闭SqlSession对象</span></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>小结：</p><ul><li>所有的增删改操作需要显示的提交事务，或者在获取SqlSession的时候显示指定开始事务自动提交。</li><li>接口所有的普通参数，尽量写实@Param参数，显示声明参数名</li><li>可以考虑使用map传递参数，方便、简单。</li><li>为了规范操作，在SQL的配置文件中，我们尽量将Parameter参数和resultType都写上。</li></ul><h2 id="4-配置文件解析"><a href="#4-配置文件解析" class="headerlink" title="4 配置文件解析"></a>4 配置文件解析</h2><blockquote><p>核心配置文件</p></blockquote><ul><li>mybatis-config.xml 系统核心配置文件。</li><li>Mybatis 的配置文件会深刻影响MyBatis行为的设置和属性信息。</li><li>配置参数如下：</li></ul><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">configuration（配置）</span><br><span class="line">properties（属性）</span><br><span class="line">settings（设置）</span><br><span class="line">typeAliases（类型别名）</span><br><span class="line">typeHandlers（类型处理器）</span><br><span class="line">objectFactory（对象工厂）</span><br><span class="line">plugins（插件）</span><br><span class="line">environments（环境配置）</span><br><span class="line">environment（环境变量）</span><br><span class="line">transactionManager（事务管理器）</span><br><span class="line">dataSource（数据源）</span><br><span class="line">databaseIdProvider（数据库厂商标识）</span><br><span class="line">mappers（映射器）</span><br><span class="line"><span class="comment">&lt;!-- 注意元素节点的顺序！顺序不对会报错 --&gt;</span></span><br></pre></td></tr></tbody></table></figure><blockquote><p>environments元素</p></blockquote><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">environments</span> <span class="attr">default</span>=<span class="string">"development"</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">environment</span> <span class="attr">id</span>=<span class="string">"development"</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">transactionManager</span> <span class="attr">type</span>=<span class="string">"JDBC"</span>/&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">dataSource</span> <span class="attr">type</span>=<span class="string">"POOLED"</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"driver"</span> <span class="attr">value</span>=<span class="string">"com.mysql.jdbc.Driver"</span>/&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"url"</span> <span class="attr">value</span>=<span class="string">"jdbc:mysql://localhost:3306/mybatis?Unicode=true<span class="symbol">&amp;amp;</span>characterEncoding=utf8"</span>/&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"username"</span> <span class="attr">value</span>=<span class="string">"root"</span>/&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"password"</span> <span class="attr">value</span>=<span class="string">"1234"</span>/&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">dataSource</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">environment</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">environments</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><ul><li><p>MyBatis可以配置多套运行环境，将SQL映射到不同的数据库上，但只能指定一个来运行，通过default来指定</p></li><li><p>子元素节点：environment</p><ul><li><p>dataSource元素使用标准的JDBC数据源接口来配置JDBC连接对象的资源，数据源是必须配置的，type可选参数如下：</p><ul><li>POOLED：使用Mybatis自带的数据库连接池来管理数据库连接，这种数据源的实现利用“池”的概念将 JDBC 连接对象组织起来 , 这是一种使得并发 Web 应用快速响应请求的流行处理方式。</li><li>UNPOOLED：不使用任何数据库连接池来管理数据库连接，即使用时请求连接，使用完关闭连接。</li><li>JNDI：jndi形式使用数据库连接、主要用于项目正常使用的时候，这个数据源的实现是为了能在如 Spring 或应用服务器这类容器中使用，容器可以集中或在外部配置数据源，然后放置一个 JNDI 上下文的引用。</li></ul></li><li><p>transactionManager 事务管理器</p></li><li><p>property 数据库连接设置</p></li></ul></li><li><p>具体环境靠id进行区分，id保证唯一！</p></li></ul><blockquote><p>mappers元素</p></blockquote><ul><li>映射器：定义映射SQL语句文件</li><li>既然 MyBatis 的行为已经由上述元素配置完了，我们现在就要来定义 SQL 映射语句了。 但首先，我们需要告诉 MyBatis 到哪里去找到这些语句。 在自动查找资源方面，Java 并没有提供一个很好的解决方案，所以最好的办法是直接告诉 MyBatis 到哪里去找映射文件。 你可以使用相对于类路径的资源引用，或完全限定资源定位符（包括 <code>file:///</code> 形式的 URL），或类名和包名等。</li></ul><p>引入资源方式，<em><strong>推荐使用第一种</strong></em></p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!-- 使用相对于类路径的资源引用 --&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">mappers</span>&gt;</span></span><br><span class="line"> <span class="tag">&lt;<span class="name">mapper</span> <span class="attr">resource</span>=<span class="string">"org/mybatis/builder/PostMapper.xml"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">mappers</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">这个已经废弃了，不用了</span><br><span class="line"><span class="comment">&lt;!-- 使用完全限定资源定位符（URL） --&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">mappers</span>&gt;</span></span><br><span class="line"> <span class="tag">&lt;<span class="name">mapper</span> <span class="attr">url</span>=<span class="string">"file:///var/mappers/AuthorMapper.xml"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">mappers</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!--</span></span><br><span class="line"><span class="comment">使用映射器接口实现类的完全限定类名</span></span><br><span class="line"><span class="comment">需要配置文件名称和接口名称一致，并且位于同一目录下</span></span><br><span class="line"><span class="comment">--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">mappers</span>&gt;</span></span><br><span class="line"> <span class="tag">&lt;<span class="name">mapper</span> <span class="attr">class</span>=<span class="string">"org.mybatis.builder.AuthorMapper"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">mappers</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!--</span></span><br><span class="line"><span class="comment">将包内的映射器接口实现全部注册为映射器</span></span><br><span class="line"><span class="comment">但是需要配置文件名称和接口名称一致，并且位于同一目录下</span></span><br><span class="line"><span class="comment">--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">mappers</span>&gt;</span></span><br><span class="line"> <span class="tag">&lt;<span class="name">package</span> <span class="attr">name</span>=<span class="string">"org.mybatis.builder"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">mappers</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p><strong>Mapper文件</strong></p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8" ?&gt;</span></span><br><span class="line"><span class="meta">&lt;!DOCTYPE <span class="meta-keyword">mapper</span></span></span><br><span class="line"><span class="meta">       <span class="meta-keyword">PUBLIC</span> <span class="meta-string">"-//mybatis.org//DTD Mapper 3.0//EN"</span></span></span><br><span class="line"><span class="meta">       <span class="meta-string">"http://mybatis.org/dtd/mybatis-3-mapper.dtd"</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">mapper</span> <span class="attr">namespace</span>=<span class="string">"com.kuang.mapper.UserMapper"</span>&gt;</span></span><br><span class="line">   </span><br><span class="line"><span class="tag">&lt;/<span class="name">mapper</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><ul><li>namespace 中文意思：命名空间，作用如下：<ul><li>namespace 的值必须为某个接口（含包名），即包名+类名</li><li>接口中的方法与映射文件中的SQL语句的id一一对应</li><li>namespace 和子元素的 id 联合保证唯一，区别不同的mapper</li></ul></li></ul><blockquote><p>Properties优化</p></blockquote><p>数据库这些属性都是可外部配置且可动态替换的，既可以在典型的 Java 属性文件中配置，亦可通过 properties 元素的子元素来传递。</p><p>优化MyBatis核心配置文件</p><ul><li>在resources目录下创建db.properties文件</li></ul><figure class="highlight properties"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="attr">driver</span>=<span class="string">com.mysql.jdbc.Driver</span></span><br><span class="line"><span class="attr">url</span>=<span class="string">jdbc:mysql://localhost:3306/mybatis?Unicode=true&amp;amp;characterEncoding=utf8</span></span><br><span class="line"><span class="attr">username</span>=<span class="string">root</span></span><br><span class="line"><span class="attr">password</span>=<span class="string">javan1996</span></span><br></pre></td></tr></tbody></table></figure><ul><li>在mybatis-config.xml配置文件中引入properties文件</li></ul><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">configuration</span>&gt;</span></span><br><span class="line">    <span class="comment">&lt;!--引入外部配置文件--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">properties</span> <span class="attr">resource</span>=<span class="string">"db.properties"</span>/&gt;</span></span><br><span class="line">    </span><br><span class="line">    <span class="tag">&lt;<span class="name">environments</span> <span class="attr">default</span>=<span class="string">"development"</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">environment</span> <span class="attr">id</span>=<span class="string">"development"</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">transactionManager</span> <span class="attr">type</span>=<span class="string">"JDBC"</span>/&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">dataSource</span> <span class="attr">type</span>=<span class="string">"POOLED"</span>&gt;</span></span><br><span class="line">                <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"driver"</span> <span class="attr">value</span>=<span class="string">"${driver}"</span>/&gt;</span></span><br><span class="line">                <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"url"</span> <span class="attr">value</span>=<span class="string">"${url}"</span>/&gt;</span></span><br><span class="line">                <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"username"</span> <span class="attr">value</span>=<span class="string">"${username}"</span>/&gt;</span></span><br><span class="line">                <span class="tag">&lt;<span class="name">property</span> <span class="attr">name</span>=<span class="string">"password"</span> <span class="attr">value</span>=<span class="string">"${password}"</span>/&gt;</span></span><br><span class="line">            <span class="tag">&lt;/<span class="name">dataSource</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">environment</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">environments</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--编写玩Mapper接口及对应的XML配置文件后，需要在MyBatis核心配置文件中注册，以下两种格式都可以--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">mappers</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">mapper</span> <span class="attr">class</span>=<span class="string">"com.bg.mapper.UserMapper"</span>/&gt;</span></span><br><span class="line"><span class="comment">&lt;!--        &lt;mapper resource="com/bg/mapper/UserMapper.xml"/&gt;--&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">mappers</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">configuration</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p><strong>注意</strong>：<strong>配置文件的配置参数是有优先级的，优先级顺序如下，如果不知道，可以通过IDEA报错提醒。</strong></p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">properties?,settings?,typeAliases?,typeHandlers?,objectFactory?,objectWrapperFactory?,reflectorFactory?,plugins?,environments?,databaseIdProvider?,mappers?</span><br></pre></td></tr></tbody></table></figure><blockquote><p>typeAliases</p></blockquote><p>类型别名可为 Java 类型设置一个缩写名字。 它仅用于 XML 配置，意在降低冗余的全限定类名书写。</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!--配置别名,注意顺序--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">typeAliases</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">typeAlias</span> <span class="attr">type</span>=<span class="string">"com.bg.pojo.User"</span> <span class="attr">alias</span>=<span class="string">"User"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">typeAliases</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>这样配置时，就可以使用 <strong>User</strong> 代替任何 <strong>com.bg.pojo.User</strong></p><p>也可以指定一个包名，MyBatis会在包名下面搜索需要的Java Bean，比如：</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">typeAliases</span>&gt;</span></span><br><span class="line">   <span class="tag">&lt;<span class="name">package</span> <span class="attr">name</span>=<span class="string">"com.bg.pojo"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">typeAliases</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>每一个在包 <strong>com.bg.pojo</strong> 中的Java Bean，在没有注解的情况下，会使用 Bean 的首字母小写的非限定类名来作为它的别名。。例如，user 作为 com.bg.pojo.User 的别名。</p><p>在实体类比较少的时候，<strong>使用第一种方式</strong>，这种可以diy别名</p><p>若实体类比较多，<strong>使用第二种方式</strong>，不可以diy，但是可以在实体类用注解名字，实现别民的diy</p><p>若有注解，则别名为其注解值，如下：<strong>注解写在实体类</strong></p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Alias("user")</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">User</span> </span>{</span><br><span class="line">  ...</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><blockquote><p>设置（settings）</p></blockquote><p>这是 MyBatis 中极为重要的调整设置，它们会改变 MyBatis 的运行时行为。具体参数含义参考官方文档。</p><p>一个配置完整的 settings 元素的示例如下：</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">settings</span>&gt;</span></span><br><span class="line">  <span class="tag">&lt;<span class="name">setting</span> <span class="attr">name</span>=<span class="string">"cacheEnabled"</span> <span class="attr">value</span>=<span class="string">"true"</span>/&gt;</span></span><br><span class="line">  <span class="tag">&lt;<span class="name">setting</span> <span class="attr">name</span>=<span class="string">"lazyLoadingEnabled"</span> <span class="attr">value</span>=<span class="string">"true"</span>/&gt;</span></span><br><span class="line">  <span class="tag">&lt;<span class="name">setting</span> <span class="attr">name</span>=<span class="string">"multipleResultSetsEnabled"</span> <span class="attr">value</span>=<span class="string">"true"</span>/&gt;</span></span><br><span class="line">  <span class="tag">&lt;<span class="name">setting</span> <span class="attr">name</span>=<span class="string">"useColumnLabel"</span> <span class="attr">value</span>=<span class="string">"true"</span>/&gt;</span></span><br><span class="line">  <span class="tag">&lt;<span class="name">setting</span> <span class="attr">name</span>=<span class="string">"useGeneratedKeys"</span> <span class="attr">value</span>=<span class="string">"false"</span>/&gt;</span></span><br><span class="line">  <span class="tag">&lt;<span class="name">setting</span> <span class="attr">name</span>=<span class="string">"autoMappingBehavior"</span> <span class="attr">value</span>=<span class="string">"PARTIAL"</span>/&gt;</span></span><br><span class="line">  <span class="tag">&lt;<span class="name">setting</span> <span class="attr">name</span>=<span class="string">"autoMappingUnknownColumnBehavior"</span> <span class="attr">value</span>=<span class="string">"WARNING"</span>/&gt;</span></span><br><span class="line">  <span class="tag">&lt;<span class="name">setting</span> <span class="attr">name</span>=<span class="string">"defaultExecutorType"</span> <span class="attr">value</span>=<span class="string">"SIMPLE"</span>/&gt;</span></span><br><span class="line">  <span class="tag">&lt;<span class="name">setting</span> <span class="attr">name</span>=<span class="string">"defaultStatementTimeout"</span> <span class="attr">value</span>=<span class="string">"25"</span>/&gt;</span></span><br><span class="line">  <span class="tag">&lt;<span class="name">setting</span> <span class="attr">name</span>=<span class="string">"defaultFetchSize"</span> <span class="attr">value</span>=<span class="string">"100"</span>/&gt;</span></span><br><span class="line">  <span class="tag">&lt;<span class="name">setting</span> <span class="attr">name</span>=<span class="string">"safeRowBoundsEnabled"</span> <span class="attr">value</span>=<span class="string">"false"</span>/&gt;</span></span><br><span class="line">  <span class="tag">&lt;<span class="name">setting</span> <span class="attr">name</span>=<span class="string">"mapUnderscoreToCamelCase"</span> <span class="attr">value</span>=<span class="string">"false"</span>/&gt;</span></span><br><span class="line">  <span class="tag">&lt;<span class="name">setting</span> <span class="attr">name</span>=<span class="string">"localCacheScope"</span> <span class="attr">value</span>=<span class="string">"SESSION"</span>/&gt;</span></span><br><span class="line">  <span class="tag">&lt;<span class="name">setting</span> <span class="attr">name</span>=<span class="string">"jdbcTypeForNull"</span> <span class="attr">value</span>=<span class="string">"OTHER"</span>/&gt;</span></span><br><span class="line">  <span class="tag">&lt;<span class="name">setting</span> <span class="attr">name</span>=<span class="string">"lazyLoadTriggerMethods"</span> <span class="attr">value</span>=<span class="string">"equals,clone,hashCode,toString"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">settings</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><blockquote><p>类型处理器（typeHandlers）</p></blockquote><p>MyBatis 在设置预处理语句（PreparedStatement）中的参数或从结果集中取出一个值时， 都会用类型处理器将获取到的值以合适的方式转换成 Java 类型。</p><blockquote><p>对象工厂（objectFactory）</p></blockquote><p>每次 MyBatis 创建结果对象的新实例时，它都会使用一个对象工厂（ObjectFactory）实例来完成实例化工作。 默认的对象工厂需要做的仅仅是实例化目标类，要么通过默认无参构造方法，要么通过存在的参数映射来调用带有参数的构造方法。</p><blockquote><p>生命周期和作用域</p></blockquote><p>理解我们之前讨论过的不同作用域和生命周期类别是至关重要的，因为错误的使用会导致非常严重的并发问题。</p><p>首先通过流程图，分析下MyBatis的执行过程：</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201126230734563.png" alt="image-20201126230734563"></p><p>作用域理解：</p><ul><li><p>SqlSessionFactoryBuilder 的作用在于创建 SqlSessionFactory，创建成功后，SqlSessionFactoryBuilder 就失去了作用，所以它只能存在于创建 SqlSessionFactory 的方法中，而不要让其长期存在。因此 <strong>SqlSessionFactoryBuilder 实例的最佳作用域是方法作用域</strong>（也就是局部方法变量）。</p></li><li><p>SqlSessionFactory 可以被认为是一个数据库连接池，它的作用是创建 SqlSession 接口对象。因为 MyBatis 的本质就是 Java 对数据库的操作，所以 SqlSessionFactory 的生命周期存在于整个 MyBatis 的应用之中，所以一旦创建了 SqlSessionFactory，就要长期保存它，直至不再使用 MyBatis 应用，<strong>所以可以认为 SqlSessionFactory 的生命周期就等同于 MyBatis 的应用周期。</strong></p></li><li><p>由于 SqlSessionFactory 是一个对数据库的连接池，所以它占据着数据库的连接资源。如果创建多个 SqlSessionFactory，那么就存在多个数据库连接池，这样不利于对数据库资源的控制，也会导致数据库连接资源被消耗光，出现系统宕机等情况，所以尽量避免发生这样的情况。</p></li><li><p>因此在一般的应用中我们往往希望 SqlSessionFactory 作为一个单例，让它在应用中被共享。所以说 <strong>SqlSessionFactory 的最佳作用域是应用作用域。</strong></p></li><li><p>如果说 SqlSessionFactory 相当于数据库连接池，那么 SqlSession 就相当于一个数据库连接（Connection 对象），你可以在一个事务里面执行多条 SQL，然后通过它的 commit、rollback 等方法，提交或者回滚事务。所以它应该存活在一个业务请求中，处理完整个请求后，应该关闭这条连接，让它归还给 SqlSessionFactory，否则数据库资源就很快被耗费精光，系统就会瘫痪，所以用 try…catch…finally… 语句来保证其正确关闭。<strong>所以 SqlSession 的最佳的作用域是请求或方法作用域。</strong></p></li></ul><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201126231936863.png" alt="image-20201126231936863"></p><h2 id="5-ResultMap"><a href="#5-ResultMap" class="headerlink" title="5 ResultMap"></a>5 ResultMap</h2><p><strong>要解决的问题，属性名和数据库表格字段名不一致问题</strong></p><p>在项目中，新建一个模块mybatis-02，内容和mybatis-01一样。</p><p>1、查看数据库user表的字段名</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201127192335229.png" alt="image-20201127192335229"></p><p>2、修改Java中的实体类，使其属性名与数据库的字段名不一致</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">User</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">int</span> id;</span><br><span class="line">    <span class="keyword">private</span> String username;</span><br><span class="line">    <span class="keyword">private</span> String password;</span><br><span class="line">......</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>3、UserMapper接口</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 根据Id查询用户</span></span><br><span class="line"><span class="function">User <span class="title">getUserById</span><span class="params">(<span class="meta">@Param("id")</span> <span class="keyword">int</span> userId)</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>4、mapper映射文件</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getUserById"</span> <span class="attr">resultType</span>=<span class="string">"User"</span>&gt;</span></span><br><span class="line">    SELECT * FROM user WHERE id = #{id}</span><br><span class="line"><span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>5、测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">getUserById</span><span class="params">()</span></span>{</span><br><span class="line"></span><br><span class="line">    SqlSession sqlSession = MyBatisTool.getSqlSession();</span><br><span class="line">    UserMapper mapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line">    User user = mapper.getUserById(<span class="number">1</span>);</span><br><span class="line">    System.out.println(user);</span><br><span class="line"></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><strong>结果：</strong></p><ul><li>User{id=1, username=’null’, password=’null’}</li><li>查询出来的结果中username和password都为空</li></ul><p><strong>分析：</strong></p><ul><li><p>SELECT * FROM user WHERE id = #{id} 可以看做</p><p>SELECT id, name, pwd FROM user WHERE id = #{id}</p></li><li><p>mybatis会根据这些查询的列名(会将列名转化为小写,数据库不区分大小写) , 去对应的实体类中查找相应列名的set方法设值 , 由于找不到setPwd() 和setname(), 所以password返回null 。</p></li></ul><blockquote><p>解决方法</p></blockquote><p>方法一：为列名指定别名，别名和java实体类的属性名一致</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getUserById"</span> <span class="attr">resultType</span>=<span class="string">"User"</span>&gt;</span></span><br><span class="line">    SELECT id, name AS username, pwd AS password FROM user WHERE id = #{id}</span><br><span class="line"><span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>查询结果</p><ul><li>User{id=1, username=’BG’, password=’123456’}</li></ul><p>方法二：使用结果集映射（ResultMap）【推荐】</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">resultMap</span> <span class="attr">id</span>=<span class="string">"UserResult"</span> <span class="attr">type</span>=<span class="string">"User"</span>&gt;</span></span><br><span class="line">    <span class="comment">&lt;!-- column是数据库表的列名 , property是对应实体类的属性名 --&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">id</span> <span class="attr">column</span>=<span class="string">"id"</span> <span class="attr">property</span>=<span class="string">"id"</span>/&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">result</span> <span class="attr">column</span>=<span class="string">"name"</span> <span class="attr">property</span>=<span class="string">"username"</span>/&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">result</span> <span class="attr">column</span>=<span class="string">"pwd"</span> <span class="attr">property</span>=<span class="string">"password"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">resultMap</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getUserById"</span> <span class="attr">resultMap</span>=<span class="string">"UserResult"</span>&gt;</span></span><br><span class="line">    SELECT * FROM user WHERE id = #{id}</span><br><span class="line"><span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p><strong>注意：select标签的返回类型为resultMap</strong></p><blockquote><p>ResultMap</p></blockquote><p><strong>自动映射</strong></p><ul><li><p><strong>resultMap</strong> 元素是 MyBatis 中最重要最强大的元素。它可以让你从 90% 的 JDBC ResultSets 数据提取代码中解放出来，并在一些情形下允许你进行一些 JDBC 不支持的操作。</p></li><li><p>实际上，在为一些比如连接的复杂语句编写映射代码的时候，一份 <strong>resultMap</strong> 能够代替实现同等功能的数千行代码。</p></li><li><p><strong>ResultMap</strong> 的设计思想是，对简单的语句做到零配置，对于复杂一点的语句，只需要描述语句之间的关系就行了。</p></li></ul><p>简单映射语句的示例，但并没有显式指定 resultMap。比如：</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"selectUserById"</span> <span class="attr">resultType</span>=<span class="string">"map"</span>&gt;</span></span><br><span class="line">select id , name , pwd</span><br><span class="line">  from user</span><br><span class="line">  where id = #{id}</span><br><span class="line"><span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>上述语句只是简单地将所有的列映射到 HashMap 的键上，这由 resultType 属性指定。虽然在大部分情况下都够用，但是 HashMap 不是一个很好的模型。你的程序更可能会使用 JavaBean 或 POJO（Plain Old Java Objects，普通老式 Java 对象）作为模型。</p><p><strong>手动映射</strong></p><p>1、设置返回值类型为resultMap</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"selectUserById"</span> <span class="attr">resultMap</span>=<span class="string">"UserResult"</span>&gt;</span></span><br><span class="line">  select id , name , pwd from user where id = #{id}</span><br><span class="line"><span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>2、编写resultMap，实现手动映射</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">resultMap</span> <span class="attr">id</span>=<span class="string">"UserResult"</span> <span class="attr">type</span>=<span class="string">"User"</span>&gt;</span></span><br><span class="line">   <span class="comment">&lt;!-- id为主键 --&gt;</span></span><br><span class="line">   <span class="tag">&lt;<span class="name">id</span> <span class="attr">column</span>=<span class="string">"id"</span> <span class="attr">property</span>=<span class="string">"id"</span>/&gt;</span></span><br><span class="line">   <span class="comment">&lt;!-- column是数据库表的列名 , property是对应实体类的属性名 --&gt;</span></span><br><span class="line">   <span class="tag">&lt;<span class="name">result</span> <span class="attr">column</span>=<span class="string">"name"</span> <span class="attr">property</span>=<span class="string">"username"</span>/&gt;</span></span><br><span class="line">   <span class="tag">&lt;<span class="name">result</span> <span class="attr">column</span>=<span class="string">"pwd"</span> <span class="attr">property</span>=<span class="string">"password"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">resultMap</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>如果世界总是这么简单就好了。但是肯定不是的，数据库中，存在一对多，多对一的情况，我们之后会使用到一些高级的结果集映射，association，collection这些。</p><h2 id="6-日志工厂"><a href="#6-日志工厂" class="headerlink" title="6 日志工厂"></a>6 日志工厂</h2><p>思考：我们在测试SQL的时候，要是能够在控制台输出 SQL 的话，是不是就能够有更快的排错效率？</p><p>如果一个数据库相关的操作出现了问题，我们可以根据输出的SQL语句快速排查问题。</p><p>对于以往的开发过程，我们会经常使用到debug模式来调节，跟踪我们的代码执行过程。但是现在使用Mybatis是基于接口，配置文件的源代码执行过程。因此，我们必须选择日志工具来作为我们开发，调节程序的工具。</p><p>Mybatis内置的日志工厂提供日志功能，具体的日志实现有以下几种工具：</p><ul><li>SLF4J</li><li>Apache Commons Logging</li><li>Log4j 2</li><li>Log4j</li><li>JDK logging</li></ul><p>具体选择哪个日志实现工具由MyBatis的内置日志工厂确定。它会使用最先找到的（按上文列举的顺序查找）。如果一个都未找到，日志功能就会被禁用。</p><p><strong>标准日志实现</strong></p><p>指定 MyBatis 应该使用哪个日志记录实现。在Mybatis核心配置文件中添加如下配置：</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">settings</span>&gt;</span></span><br><span class="line">       <span class="tag">&lt;<span class="name">setting</span> <span class="attr">name</span>=<span class="string">"logImpl"</span> <span class="attr">value</span>=<span class="string">"STDOUT_LOGGING"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">settings</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>然后，测试，可以看到控制台有大量日志输出！</p><blockquote><p>Log4j</p></blockquote><p><strong>简介：</strong></p><ul><li>Log4j是Apache的一个开源项目</li><li>通过使用Log4j，我们可以控制日志信息输送的目的地：控制台，文本，GUI组件….</li><li>我们也可以控制每一条日志的输出格式；</li><li>通过定义每一条日志信息的级别，我们能够更加细致地控制日志的生成过程。最令人感兴趣的就是，这些可以通过一个配置文件来灵活地进行配置，而不需要修改应用的代码。</li></ul><p><strong>使用步骤：</strong></p><p>1、导入log4j的jar包，在父工程的pom.xml或者当前子模块的pom.xml添加</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!--日志--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>log4j<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>log4j<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">version</span>&gt;</span>1.2.17<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>2、编写配置文件</p><p>配置文件格式基本固定，百度也有很多资料可以参考，我们仅需找到一份适合自己的保存起来。</p><p>配置文件放在resources目录下，log4j.properties</p><figure class="highlight properties"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">#将等级为DEBUG的日志信息输出到console和file这两个目的地，console和file的定义在下面的代码</span></span><br><span class="line"><span class="meta">log4j.rootLogger</span>=<span class="string">DEBUG,console,file</span></span><br><span class="line"></span><br><span class="line"><span class="comment">#控制台输出的相关设置</span></span><br><span class="line"><span class="meta">log4j.appender.console</span> = <span class="string">org.apache.log4j.ConsoleAppender</span></span><br><span class="line"><span class="meta">log4j.appender.console.Target</span> = <span class="string">System.out</span></span><br><span class="line"><span class="meta">log4j.appender.console.Threshold</span>=<span class="string">DEBUG</span></span><br><span class="line"><span class="meta">log4j.appender.console.layout</span> = <span class="string">org.apache.log4j.PatternLayout</span></span><br><span class="line"><span class="meta">log4j.appender.console.layout.ConversionPattern</span>=<span class="string">[%c]-%m%n</span></span><br><span class="line"></span><br><span class="line"><span class="comment">#文件输出的相关设置</span></span><br><span class="line"><span class="meta">log4j.appender.file</span> = <span class="string">org.apache.log4j.RollingFileAppender</span></span><br><span class="line"><span class="meta">log4j.appender.file.File</span>=<span class="string">./log/bg.log</span></span><br><span class="line"><span class="meta">log4j.appender.file.MaxFileSize</span>=<span class="string">10mb</span></span><br><span class="line"><span class="meta">log4j.appender.file.Threshold</span>=<span class="string">DEBUG</span></span><br><span class="line"><span class="meta">log4j.appender.file.layout</span>=<span class="string">org.apache.log4j.PatternLayout</span></span><br><span class="line"><span class="meta">log4j.appender.file.layout.ConversionPattern</span>=<span class="string">[%p][%d{yy-MM-dd}][%c]%m%n</span></span><br><span class="line"></span><br><span class="line"><span class="comment">#日志输出级别</span></span><br><span class="line"><span class="meta">log4j.logger.org.mybatis</span>=<span class="string">DEBUG</span></span><br><span class="line"><span class="meta">log4j.logger.java.sql</span>=<span class="string">DEBUG</span></span><br><span class="line"><span class="meta">log4j.logger.java.sql.Statement</span>=<span class="string">DEBUG</span></span><br><span class="line"><span class="meta">log4j.logger.java.sql.ResultSet</span>=<span class="string">DEBUG</span></span><br><span class="line"><span class="meta">log4j.logger.java.sql.PreparedStatement</span>=<span class="string">DEBUG</span></span><br></pre></td></tr></tbody></table></figure><p>3、setting设置日志实现</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!--Log4j日志--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">settings</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">setting</span> <span class="attr">name</span>=<span class="string">"logImpl"</span> <span class="attr">value</span>=<span class="string">"LOG4J"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">settings</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>4、在程序中使用Log4j进行日志输出！</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span> com.bg.mapper.UserMapper;</span><br><span class="line"><span class="keyword">import</span> com.bg.pojo.User;</span><br><span class="line"><span class="keyword">import</span> com.bg.tools.MyBatisTool;</span><br><span class="line"><span class="keyword">import</span> org.apache.ibatis.session.SqlSession;</span><br><span class="line"><span class="keyword">import</span> org.apache.log4j.Logger;</span><br><span class="line"><span class="keyword">import</span> org.junit.Test;</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">MyTest</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="keyword">static</span> Logger logger = Logger.getLogger(MyTest.class);</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Test</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">getUserById</span><span class="params">()</span></span>{</span><br><span class="line"></span><br><span class="line">        logger.info(<span class="string">"info：进入selectUser方法"</span>);</span><br><span class="line">        logger.debug(<span class="string">"debug：进入selectUser方法"</span>);</span><br><span class="line">        logger.error(<span class="string">"error: 进入selectUser方法"</span>);</span><br><span class="line"></span><br><span class="line">        SqlSession sqlSession = MyBatisTool.getSqlSession();</span><br><span class="line">        UserMapper mapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line">        User user = mapper.getUserById(<span class="number">1</span>);</span><br><span class="line">        System.out.println(user);</span><br><span class="line"></span><br><span class="line">        sqlSession.close();</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>5、测试，看控制台输出</p><ul><li>控制台输出日志</li><li>还生成了一个日志文件夹</li></ul><h2 id="7-LIMIT分页"><a href="#7-LIMIT分页" class="headerlink" title="7 LIMIT分页"></a>7 LIMIT分页</h2><p><strong>为什么需要分页？</strong></p><p>在对数据库进行大量数据查询时，往往需要使用分页进行查询，每次处理小部分数据，这样对数据库的压力在可控范围内。</p><p>使用LIMIT分页的常用语法</p><figure class="highlight sql"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">#数据库索引是从<span class="number">0</span>开始</span><br><span class="line"><span class="keyword">SELECT</span> <span class="operator">*</span> <span class="keyword">FROM</span> <span class="keyword">table</span> LIMIT stratIndex，pageSize</span><br><span class="line"></span><br><span class="line"><span class="keyword">SELECT</span> <span class="operator">*</span> <span class="keyword">FROM</span> <span class="keyword">table</span> LIMIT <span class="number">5</span>,<span class="number">10</span>; <span class="operator">/</span><span class="operator">/</span> 检索记录行 <span class="number">6</span><span class="number">-15</span>  </span><br><span class="line"></span><br><span class="line">#为了检索从某一个偏移量到记录集的结束所有的记录行，可以指定第二个参数为 <span class="number">-1</span>，在最小的mysql版本中，该语法可以使用</span><br><span class="line">#在新的mysql版本  <span class="number">-1</span>参数已经不允许使用了</span><br><span class="line"><span class="keyword">SELECT</span> <span class="operator">*</span> <span class="keyword">FROM</span> <span class="keyword">table</span> LIMIT <span class="number">95</span>,<span class="number">-1</span>; <span class="operator">/</span><span class="operator">/</span> 检索记录行 <span class="number">96</span><span class="operator">-</span>last.  </span><br><span class="line"></span><br><span class="line">#如果只给定一个参数，它表示返回最大的记录行数目：   </span><br><span class="line"><span class="keyword">SELECT</span> <span class="operator">*</span> <span class="keyword">FROM</span> <span class="keyword">table</span> LIMIT <span class="number">5</span>; <span class="operator">/</span><span class="operator">/</span>检索前 <span class="number">5</span> 个记录行  </span><br><span class="line"></span><br><span class="line">#换句话说，LIMIT n 等价于 LIMIT <span class="number">0</span>,n。 </span><br></pre></td></tr></tbody></table></figure><p><strong>使用LIMIT进行分页：</strong></p><p><strong>步骤：</strong></p><p>1、在UserMapper.java接口中，编写函数</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 分页查询</span></span><br><span class="line"><span class="function">List&lt;User&gt; <span class="title">getUserByLimit</span><span class="params">(Map map)</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>2、编写UserMapper.xml文件，传入参数类型为map</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">resultMap</span> <span class="attr">id</span>=<span class="string">"UserResult"</span> <span class="attr">type</span>=<span class="string">"User"</span>&gt;</span></span><br><span class="line">    <span class="comment">&lt;!-- column是数据库表的列名 , property是对应实体类的属性名 --&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">id</span> <span class="attr">column</span>=<span class="string">"id"</span> <span class="attr">property</span>=<span class="string">"id"</span>/&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">result</span> <span class="attr">column</span>=<span class="string">"name"</span> <span class="attr">property</span>=<span class="string">"username"</span>/&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">result</span> <span class="attr">column</span>=<span class="string">"pwd"</span> <span class="attr">property</span>=<span class="string">"password"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">resultMap</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getUserByLimit"</span> <span class="attr">parameterType</span>=<span class="string">"map"</span> <span class="attr">resultMap</span>=<span class="string">"UserResult"</span>&gt;</span></span><br><span class="line">    SELECT * FROM user LIMIT #{startIndex}, #{pageSize}</span><br><span class="line"><span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>3、测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">getUserByLimit</span><span class="params">()</span></span>{</span><br><span class="line">    SqlSession sqlSession = MyBatisTool.getSqlSession();</span><br><span class="line">    UserMapper mapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line">    <span class="comment">// 分页,查询第一页，页面大小为2</span></span><br><span class="line">    <span class="keyword">int</span> pageIndex = <span class="number">1</span>;</span><br><span class="line">    <span class="keyword">int</span> pageSize = <span class="number">2</span>;</span><br><span class="line">    <span class="comment">// 用map准备参数</span></span><br><span class="line">    Map&lt;String, Integer&gt; map = <span class="keyword">new</span> HashMap&lt;String, Integer&gt;();</span><br><span class="line">    <span class="comment">//计算起始索引</span></span><br><span class="line">    <span class="keyword">int</span> startIndex = (pageIndex - <span class="number">1</span>) * pageSize;</span><br><span class="line">    map.put(<span class="string">"startIndex"</span>, startIndex);</span><br><span class="line">    map.put(<span class="string">"pageSize"</span>, pageSize);</span><br><span class="line">    <span class="comment">// 执行查询</span></span><br><span class="line">    List&lt;User&gt; userList = mapper.getUserByLimit(map);</span><br><span class="line">    <span class="keyword">for</span> (User user : userList) {</span><br><span class="line">        System.out.println(user);</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><strong>使用RowBounds分页：</strong>【了解】</p><p>我们除了使用Limit在SQL层面实现分页，也可以使用RowBounds在Java代码层面实现分页。</p><p>1、在UserMapper.java接口中，编写函数</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// RowBounds分页</span></span><br><span class="line"><span class="function">List&lt;User&gt; <span class="title">getUserListByRowBounds</span><span class="params">()</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>2、编写UserMapper.xml文件，传入参数类型为map</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">resultMap</span> <span class="attr">id</span>=<span class="string">"UserResult"</span> <span class="attr">type</span>=<span class="string">"User"</span>&gt;</span></span><br><span class="line">    <span class="comment">&lt;!-- column是数据库表的列名 , property是对应实体类的属性名 --&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">id</span> <span class="attr">column</span>=<span class="string">"id"</span> <span class="attr">property</span>=<span class="string">"id"</span>/&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">result</span> <span class="attr">column</span>=<span class="string">"name"</span> <span class="attr">property</span>=<span class="string">"username"</span>/&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">result</span> <span class="attr">column</span>=<span class="string">"pwd"</span> <span class="attr">property</span>=<span class="string">"password"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">resultMap</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getUserListByRowBounds"</span> <span class="attr">resultMap</span>=<span class="string">"UserResult"</span>&gt;</span></span><br><span class="line">    SELECT * FROM user</span><br><span class="line"><span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>3、测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">getUserListByRowBounds</span><span class="params">()</span></span>{</span><br><span class="line">    SqlSession sqlSession = MyBatisTool.getSqlSession();</span><br><span class="line">    <span class="keyword">int</span> pageIndex = <span class="number">1</span>;</span><br><span class="line">    <span class="keyword">int</span> pageSize = <span class="number">2</span>;</span><br><span class="line">    RowBounds rowBounds = <span class="keyword">new</span> RowBounds((pageIndex - <span class="number">1</span>) * pageSize, pageSize);</span><br><span class="line">    List&lt;User&gt; userList = sqlSession.selectList(<span class="string">"com.bg.mapper.UserMapper.getUserListByRowBounds"</span>, <span class="keyword">null</span>, rowBounds);</span><br><span class="line">    <span class="keyword">for</span> (User user : userList) {</span><br><span class="line">        System.out.println(user);</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><strong>使用插件进行分页：</strong></p><p><strong>PageHelper</strong>自行了解。</p><h2 id="8-使用注解开发"><a href="#8-使用注解开发" class="headerlink" title="8 使用注解开发"></a>8 使用注解开发</h2><blockquote><p>面向接口编程</p></blockquote><ul><li>在面向对象编程中，通常我们都是面向接口编程</li><li><strong>根本原因：解耦，可扩展，提高复用，分层开发，上层写接口，不用管具体的实现，大家遵循共同的标准，使得开发变得容易，规范性更好。</strong></li><li>在一个面向对象的系统中，系统的各个功能模块是由许许多多的不同对象协作完成，在这种情况下，各个对象内部如何实现自己的，对系统设计人员来讲就不那么重要了。</li><li>而各个对象之间的协作关系则成为系统设计的关键。小到不同类之间的通信，大到各模块之间的交互，在系统设计之初都是要着重考虑的，这也是系统设计的主要工作内容。面向接口编程就是指按照这种思想来编程。</li></ul><p><strong>关于接口的理解</strong></p><ul><li><p>接口从更深层次的理解，应是定义（规范、约束）与实现的分离。</p></li><li><p>接口的本身反映了系统设计人员对系统的抽象理解。</p></li><li><p>接口应有两类：</p><ul><li>第一类是对一个个体的抽象，它可对应为一个抽象体（abstract class）；</li><li>第二类是对一个个体某一方面的抽象，即形成一个抽象面（interface）；</li></ul></li><li><p>一个个体可能由多个抽象面。抽象体与抽象面是有区别的。</p></li></ul><p><strong>三个面向区别</strong></p><ul><li>面向对象是指，我们考虑问题时，以对象为单位，考虑对象的属性及方法。</li><li>面向过程是指，我们考虑问题时，以一个具体的流程为单位，考虑它的实现</li><li>接口设计与非接口设计是针对复用技术而言的，与面向对象（过程）不是一个问题，更多的体现就是对系统整体的架构。</li></ul><blockquote><p>利用注解开发</p></blockquote><ul><li><p><strong>mybatis最初配置信息是基于 XML ,映射语句(SQL)也是定义在 XML 中的。而到MyBatis 3提供了新的基于注解的配置。不幸的是，Java 注解的的表达力和灵活性十分有限。最强大的 MyBatis 映射并不能用注解来构建</strong></p></li><li><p>sql 类型主要有 :</p></li><li><ul><li>@select ()</li><li>@update ()</li><li>@Insert ()</li><li>@delete ()</li></ul></li></ul><p><strong>注意：</strong>利用注解开发就不需要UserMapper.xml映射文件了 。</p><p>依然新建一个模块mybatis-03来学习这方面的知识，内容拷贝mybatis-01的即可。</p><p>1、UserMapper.java接口中添加注解</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 查询表格中的所有用户</span></span><br><span class="line"><span class="meta">@Select("SELECT * FROM user")</span></span><br><span class="line"><span class="function">List&lt;User&gt; <span class="title">getUserList</span><span class="params">()</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>2、在mybatis核心配置文件中注册mapper</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">mappers</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">mapper</span> <span class="attr">class</span>=<span class="string">"com.bg.mapper.UserMapper"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">mappers</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>3、测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">getUserList</span><span class="params">()</span></span>{</span><br><span class="line"></span><br><span class="line">    SqlSession sqlSession = MyBatisTool.getSqlSession();</span><br><span class="line">    UserMapper mapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line">    List&lt;User&gt; userList = mapper.getUserList();</span><br><span class="line">    <span class="keyword">for</span> (User user : userList) {</span><br><span class="line">        System.out.println(user.toString());</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><strong>详解Mybatis执行流程：</strong></p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/mybatis.png" alt="mybatis"></p><blockquote><p>注解实现增删改查</p></blockquote><p>首先需要改造MyBatisTool工具类中的getSession()方法，开始事务自动提交。</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 获取SqlSession实例，用来操作数据库，默认开启事务自动提交</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> SqlSession <span class="title">getSqlSession</span><span class="params">()</span></span>{</span><br><span class="line">    <span class="keyword">return</span> sqlSessionFactory.openSession(<span class="keyword">true</span>);</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> SqlSession <span class="title">getSqlSession</span><span class="params">(<span class="keyword">boolean</span> flag)</span></span>{</span><br><span class="line">    <span class="keyword">return</span> sqlSessionFactory.openSession(flag);</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><strong>根据ID查询用户：</strong></p><p>1、UserMapper.java接口中添加注解</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 根据Id查询用户</span></span><br><span class="line"><span class="meta">@Select("SELECT * FROM user WHERE id = #{id}")</span></span><br><span class="line"><span class="function">User <span class="title">getUserById</span><span class="params">(<span class="meta">@Param("id")</span> <span class="keyword">int</span> userId)</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>2、测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">getUserById</span><span class="params">()</span></span>{</span><br><span class="line"></span><br><span class="line">    SqlSession sqlSession = MyBatisTool.getSqlSession();</span><br><span class="line">    UserMapper mapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line">    User user = mapper.getUserById(<span class="number">1</span>);</span><br><span class="line">    System.out.println(user.toString());</span><br><span class="line"></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><strong>增加一个用户：</strong></p><p>1、UserMapper.java接口中添加注解</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 增加一个用户</span></span><br><span class="line"><span class="meta">@Insert("INSERT INTO user(id, name, pwd) VALUES(#{id}, #{name}, #{pwd})")</span></span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">addUser</span><span class="params">(User user)</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>2、测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">addUser</span><span class="params">()</span></span>{</span><br><span class="line"></span><br><span class="line">    SqlSession sqlSession = MyBatisTool.getSqlSession();</span><br><span class="line">    UserMapper mapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line">    User user = <span class="keyword">new</span> User(<span class="number">2</span>, <span class="string">"马保国"</span>,<span class="string">"WuDe"</span>);</span><br><span class="line">    <span class="keyword">int</span> i = mapper.addUser(user);</span><br><span class="line">    <span class="keyword">if</span>(i  == <span class="number">1</span>){</span><br><span class="line">        System.out.println(<span class="string">"插入用户成功"</span>);</span><br><span class="line">    }<span class="keyword">else</span>{</span><br><span class="line">        System.out.println(<span class="string">"插入用户失败"</span>);</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><strong>修改一个用户：</strong></p><p>1、UserMapper.java接口中添加注解</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 修改一个用户</span></span><br><span class="line"><span class="meta">@Update("UPDATE user SET name = #{name}, pwd = #{pwd} WHERE id = #{id}")</span></span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">updateUser</span><span class="params">(User user)</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>2、测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">UpdateUser</span><span class="params">()</span></span>{</span><br><span class="line"></span><br><span class="line">    SqlSession sqlSession = MyBatisTool.getSqlSession();</span><br><span class="line">    UserMapper mapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line">    User user = <span class="keyword">new</span> User(<span class="number">3</span>, <span class="string">"张三"</span>,<span class="string">"526553"</span>);</span><br><span class="line">    <span class="keyword">int</span> i = mapper.updateUser(user);</span><br><span class="line">    <span class="keyword">if</span>(i  == <span class="number">1</span>){</span><br><span class="line">        System.out.println(<span class="string">"更新用户成功"</span>);</span><br><span class="line">    }<span class="keyword">else</span>{</span><br><span class="line">        System.out.println(<span class="string">"更新用户失败"</span>);</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><strong>删除一个用户：</strong></p><p>1、UserMapper.java接口中添加注解</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 删除一个用户</span></span><br><span class="line"><span class="meta">@Delete("DELETE FROM user WHERE id = #{id}")</span></span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">deleteUser</span><span class="params">(<span class="meta">@Param("id")</span> <span class="keyword">int</span> userId)</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>2、测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">deleteUser</span><span class="params">()</span></span>{</span><br><span class="line"></span><br><span class="line">    SqlSession sqlSession = MyBatisTool.getSqlSession();</span><br><span class="line">    UserMapper mapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line">    <span class="keyword">int</span> i = mapper.deleteUser(<span class="number">5</span>);</span><br><span class="line">    <span class="keyword">if</span>(i  == <span class="number">1</span>){</span><br><span class="line">        System.out.println(<span class="string">"删除用户成功"</span>);</span><br><span class="line">    }<span class="keyword">else</span>{</span><br><span class="line">        System.out.println(<span class="string">"删除用户失败"</span>);</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><blockquote><p>关于@Param</p></blockquote><p>@Param注解用于给方法参数起一个名字。以下是总结的使用原则：</p><ul><li>在方法只接受一个参数的情况下，可以不使用@Param。</li><li>在方法接受多个参数的情况下，建议一定要使用@Param注解给参数命名。</li><li>如果参数是 JavaBean ， 则不能使用@Param。</li></ul><blockquote><p>#与$的区别</p></blockquote><ul><li><p>#{} 的作用主要是替换预编译语句(PrepareStatement)中的占位符? 【推荐使用】</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">INSERT INTO user (name) VALUES (#{name});</span><br><span class="line">INSERT INTO user (name) VALUES (?);</span><br></pre></td></tr></tbody></table></figure></li><li><p>${} 的作用是直接进行字符串替换</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">INSERT INTO user (name) VALUES ('${name}');</span><br><span class="line">INSERT INTO user (name) VALUES ('kuangshen');</span><br></pre></td></tr></tbody></table></figure></li></ul><blockquote><p>使用注解和配置文件协同开发，才是MyBatis的最佳实践！</p></blockquote><h2 id="9-一对多和多对一处理"><a href="#9-一对多和多对一处理" class="headerlink" title="9 一对多和多对一处理"></a>9 一对多和多对一处理</h2><blockquote><p>多对一处理</p></blockquote><p>多个学生对应一个老师</p><blockquote><p>数据库设计</p></blockquote><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201210170844181.png" alt="image-20201210170844181"></p><figure class="highlight sql"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">CREATE</span> <span class="keyword">TABLE</span> `teacher` (</span><br><span class="line">`id` <span class="type">INT</span>(<span class="number">10</span>) <span class="keyword">NOT</span> <span class="keyword">NULL</span>,</span><br><span class="line">`name` <span class="type">VARCHAR</span>(<span class="number">30</span>) <span class="keyword">DEFAULT</span> <span class="keyword">NULL</span>,</span><br><span class="line"><span class="keyword">PRIMARY</span> KEY (`id`)</span><br><span class="line">) ENGINE<span class="operator">=</span>INNODB <span class="keyword">DEFAULT</span> CHARSET<span class="operator">=</span>utf8</span><br><span class="line"></span><br><span class="line"><span class="keyword">INSERT</span> <span class="keyword">INTO</span> teacher(`id`, `name`) <span class="keyword">VALUES</span> (<span class="number">1</span>, <span class="string">'曾老师'</span>);</span><br><span class="line"></span><br><span class="line"><span class="keyword">CREATE</span> <span class="keyword">TABLE</span> `student` (</span><br><span class="line">`id` <span class="type">INT</span>(<span class="number">10</span>) <span class="keyword">NOT</span> <span class="keyword">NULL</span>,</span><br><span class="line">`name` <span class="type">VARCHAR</span>(<span class="number">30</span>) <span class="keyword">DEFAULT</span> <span class="keyword">NULL</span>,</span><br><span class="line">`tid` <span class="type">INT</span>(<span class="number">10</span>) <span class="keyword">DEFAULT</span> <span class="keyword">NULL</span>,</span><br><span class="line"><span class="keyword">PRIMARY</span> KEY (`id`),</span><br><span class="line">KEY `fktid` (`tid`),</span><br><span class="line"><span class="keyword">CONSTRAINT</span> `fktid` <span class="keyword">FOREIGN</span> KEY (`tid`) <span class="keyword">REFERENCES</span> `teacher` (`id`)</span><br><span class="line">) ENGINE<span class="operator">=</span>INNODB <span class="keyword">DEFAULT</span> CHARSET<span class="operator">=</span>utf8</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"><span class="keyword">INSERT</span> <span class="keyword">INTO</span> `student` (`id`, `name`, `tid`) <span class="keyword">VALUES</span> (<span class="string">'1'</span>, <span class="string">'小明'</span>, <span class="string">'1'</span>);</span><br><span class="line"><span class="keyword">INSERT</span> <span class="keyword">INTO</span> `student` (`id`, `name`, `tid`) <span class="keyword">VALUES</span> (<span class="string">'2'</span>, <span class="string">'小红'</span>, <span class="string">'1'</span>);</span><br><span class="line"><span class="keyword">INSERT</span> <span class="keyword">INTO</span> `student` (`id`, `name`, `tid`) <span class="keyword">VALUES</span> (<span class="string">'3'</span>, <span class="string">'小张'</span>, <span class="string">'1'</span>);</span><br><span class="line"><span class="keyword">INSERT</span> <span class="keyword">INTO</span> `student` (`id`, `name`, `tid`) <span class="keyword">VALUES</span> (<span class="string">'4'</span>, <span class="string">'小李'</span>, <span class="string">'1'</span>);</span><br><span class="line"><span class="keyword">INSERT</span> <span class="keyword">INTO</span> `student` (`id`, `name`, `tid`) <span class="keyword">VALUES</span> (<span class="string">'5'</span>, <span class="string">'小王'</span>, <span class="string">'1'</span>);</span><br></pre></td></tr></tbody></table></figure><blockquote><p>搭建测试环境</p></blockquote><p>1、编写实体类</p><p>Student.java</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.pojo;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Student</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">int</span> id;</span><br><span class="line">    <span class="keyword">private</span> String name;</span><br><span class="line">    <span class="keyword">private</span> Teacher teacher;</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="title">Student</span><span class="params">()</span> </span>{</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="title">Student</span><span class="params">(<span class="keyword">int</span> id, String name, Teacher teacher)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.id = id;</span><br><span class="line">        <span class="keyword">this</span>.name = name;</span><br><span class="line">        <span class="keyword">this</span>.teacher = teacher;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">getId</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> id;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setId</span><span class="params">(<span class="keyword">int</span> id)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.id = id;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">getName</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> name;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setName</span><span class="params">(String name)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.name = name;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> Teacher <span class="title">getTeacher</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> teacher;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setTeacher</span><span class="params">(Teacher teacher)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.teacher = teacher;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">toString</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> <span class="string">"Student{"</span> +</span><br><span class="line">                <span class="string">"id="</span> + id +</span><br><span class="line">                <span class="string">", name='"</span> + name + <span class="string">'\''</span> +</span><br><span class="line">                <span class="string">", teacher="</span> + teacher +</span><br><span class="line">                <span class="string">'}'</span>;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>Teacher.java</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.pojo;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Teacher</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">int</span> id;</span><br><span class="line">    <span class="keyword">private</span> String name;</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="title">Teacher</span><span class="params">()</span> </span>{</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="title">Teacher</span><span class="params">(<span class="keyword">int</span> id, String name)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.id = id;</span><br><span class="line">        <span class="keyword">this</span>.name = name;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">getId</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> id;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setId</span><span class="params">(<span class="keyword">int</span> id)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.id = id;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">getName</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> name;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setName</span><span class="params">(String name)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.name = name;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">toString</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> <span class="string">"Teacher{"</span> +</span><br><span class="line">                <span class="string">"id="</span> + id +</span><br><span class="line">                <span class="string">", name='"</span> + name + <span class="string">'\''</span> +</span><br><span class="line">                <span class="string">'}'</span>;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>2、编写实体类对应的Mapper接口</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.dao;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">StudentMapper</span> </span>{</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.dao;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">TeacherMapper</span> </span>{</span><br><span class="line">    </span><br><span class="line">}</span><br><span class="line"></span><br></pre></td></tr></tbody></table></figure><p>3、编写接口对应的mapper.xml配置文件</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8" ?&gt;</span></span><br><span class="line"><span class="meta">&lt;!DOCTYPE <span class="meta-keyword">mapper</span></span></span><br><span class="line"><span class="meta">       <span class="meta-keyword">PUBLIC</span> <span class="meta-string">"-//mybatis.org//DTD Mapper 3.0//EN"</span></span></span><br><span class="line"><span class="meta">       <span class="meta-string">"http://mybatis.org/dtd/mybatis-3-mapper.dtd"</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">mapper</span> <span class="attr">namespace</span>=<span class="string">"com.zzb.dao.StudentMapper"</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">mapper</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8" ?&gt;</span></span><br><span class="line"><span class="meta">&lt;!DOCTYPE <span class="meta-keyword">mapper</span></span></span><br><span class="line"><span class="meta">       <span class="meta-keyword">PUBLIC</span> <span class="meta-string">"-//mybatis.org//DTD Mapper 3.0//EN"</span></span></span><br><span class="line"><span class="meta">       <span class="meta-string">"http://mybatis.org/dtd/mybatis-3-mapper.dtd"</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">mapper</span> <span class="attr">namespace</span>=<span class="string">"com.zzb.dao.TeacherMapper"</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">mapper</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><blockquote><p>按查询嵌套处理</p></blockquote><p>1、给 StudentMapper 接口增加方法</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 获取学生列表及对应老师的信息</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> List&lt;Student&gt; <span class="title">getStudents</span><span class="params">()</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>2、编写对应的Mapper配置文件</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8" ?&gt;</span></span><br><span class="line"><span class="meta">&lt;!DOCTYPE <span class="meta-keyword">mapper</span></span></span><br><span class="line"><span class="meta">        <span class="meta-keyword">PUBLIC</span> <span class="meta-string">"-//mybatis.org//DTD Config 3.0//EN"</span></span></span><br><span class="line"><span class="meta">        <span class="meta-string">"http://mybatis.org/dtd/mybatis-3-mapper.dtd"</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">mapper</span> <span class="attr">namespace</span>=<span class="string">"com.zzb.dao.StudentMapper"</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">&lt;!--按查询嵌套--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getStudents"</span> <span class="attr">resultMap</span>=<span class="string">"StudentTeacher"</span>&gt;</span></span><br><span class="line">        select * from student;</span><br><span class="line">    <span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">resultMap</span> <span class="attr">id</span>=<span class="string">"StudentTeacher"</span> <span class="attr">type</span>=<span class="string">"Student"</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">result</span> <span class="attr">property</span>=<span class="string">"id"</span> <span class="attr">column</span>=<span class="string">"id"</span>/&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">result</span> <span class="attr">property</span>=<span class="string">"name"</span> <span class="attr">column</span>=<span class="string">"name"</span>/&gt;</span></span><br><span class="line">        <span class="comment">&lt;!--association关联属性 property属性名 javaType属性类型 column在多的一方的表中的列名--&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">association</span>  <span class="attr">property</span>=<span class="string">"teacher"</span> <span class="attr">column</span>=<span class="string">"tid"</span> <span class="attr">javaType</span>=<span class="string">"Teacher"</span> <span class="attr">select</span> = <span class="string">"getTeacher"</span>/&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">resultMap</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getTeacher"</span> <span class="attr">resultType</span>=<span class="string">"Teacher"</span>&gt;</span></span><br><span class="line">        select * from teacher where id = #{tid}</span><br><span class="line">    <span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">mapper</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>3、MyBatis配置文件中注册Mapper</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!--绑定接口--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">mappers</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">mapper</span> <span class="attr">class</span>=<span class="string">"com.zzb.dao.StudentMapper"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">mappers</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p><strong>注意：</strong></p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">resultMap</span> <span class="attr">id</span>=<span class="string">"StudentTeacher"</span> <span class="attr">type</span>=<span class="string">"Student"</span>&gt;</span></span><br><span class="line">   <span class="comment">&lt;!--association关联属性 property属性名 javaType属性类型 column在多的一方的表中的列名--&gt;</span></span><br><span class="line">   <span class="tag">&lt;<span class="name">association</span> <span class="attr">property</span>=<span class="string">"teacher"</span>  <span class="attr">column</span>=<span class="string">"{id = tid, name = name}"</span> <span class="attr">javaType</span>=<span class="string">"Teacher"</span> <span class="attr">select</span>=<span class="string">"getTeacher"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">resultMap</span>&gt;</span></span><br><span class="line"><span class="comment">&lt;!--</span></span><br><span class="line"><span class="comment">这里传递过来的id，只有一个属性的时候，下面可以写任何值</span></span><br><span class="line"><span class="comment">association中column多参数配置：</span></span><br><span class="line"><span class="comment">   column="{key=value,key=value}"</span></span><br><span class="line"><span class="comment">   其实就是键值对的形式，key是传给下个sql的取值名称，value是sql查询的字段名。</span></span><br><span class="line"><span class="comment">--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getTeacher"</span> <span class="attr">resultType</span>=<span class="string">"teacher"</span>&gt;</span></span><br><span class="line">  select * from teacher where id = #{id} and name = #{name}</span><br><span class="line"><span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>4、测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">getStudent</span><span class="params">()</span></span>{</span><br><span class="line">    SqlSession sqlSession = MybatisUtils.getSqlSession();</span><br><span class="line">    StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);</span><br><span class="line">    List&lt;Student&gt; studentList = studentMapper.getStudents();</span><br><span class="line"></span><br><span class="line">    <span class="keyword">for</span>(Student student : studentList){</span><br><span class="line">        System.out.println(student);</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>测试结果：</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">Student{id=1, name='小明', teacher=Teacher{id=1, name='曾老师'}}</span><br><span class="line">Student{id=2, name='小红', teacher=Teacher{id=1, name='曾老师'}}</span><br><span class="line">Student{id=3, name='小张', teacher=Teacher{id=1, name='曾老师'}}</span><br><span class="line">Student{id=4, name='小李', teacher=Teacher{id=1, name='曾老师'}}</span><br><span class="line">Student{id=5, name='小王', teacher=Teacher{id=1, name='曾老师'}}</span><br></pre></td></tr></tbody></table></figure><blockquote><p>按结果嵌套查询</p></blockquote><p>1、StudentMapper接口方法编写</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> List&lt;Student&gt; <span class="title">getStudents2</span><span class="params">()</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>2、编写对应的StudentMapper.xml配置文件</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line">&lt;!--按结果嵌套--&gt;</span><br><span class="line">&lt;select id="getStudents2" resultMap="StudentTeacher2"&gt;</span><br><span class="line">SELECT S.id AS sid, s.name AS sname, t.id AS tid, t.name AS tname</span><br><span class="line">FROM student AS s, teacher AS t</span><br><span class="line">WHERE s.tid = t.id;</span><br><span class="line">&lt;/select&gt;</span><br><span class="line"></span><br><span class="line">&lt;resultMap id="StudentTeacher2" type="Student"&gt;</span><br><span class="line">    &lt;result property="id" column="sid"/&gt;</span><br><span class="line">    &lt;result property="name" column="sname"/&gt;</span><br><span class="line">    &lt;association property="teacher" javaType="Teacher"&gt;</span><br><span class="line">        &lt;result property="id" column="tid"/&gt;</span><br><span class="line">        &lt;result property="name" column="tname"/&gt;</span><br><span class="line">    &lt;/association&gt;</span><br><span class="line"></span><br><span class="line">&lt;/resultMap&gt;</span><br></pre></td></tr></tbody></table></figure><p>3、MyBatis配置文件中注册Mapper</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">mapper</span> <span class="attr">class</span>=<span class="string">"com.zzb.dao.StudentMapper"</span>/&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>4、测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">getStudent2</span><span class="params">()</span></span>{</span><br><span class="line">    SqlSession sqlSession = MybatisUtils.getSqlSession();</span><br><span class="line">    StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);</span><br><span class="line">    List&lt;Student&gt; studentList = studentMapper.getStudents2();</span><br><span class="line">    <span class="keyword">for</span>(Student student : studentList){</span><br><span class="line">        System.out.println(student);</span><br><span class="line">    }</span><br><span class="line">    </span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>测试结果：</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">Student{id=1, name='小明', teacher=Teacher{id=1, name='曾老师'}}</span><br><span class="line">Student{id=2, name='小红', teacher=Teacher{id=1, name='曾老师'}}</span><br><span class="line">Student{id=3, name='小张', teacher=Teacher{id=1, name='曾老师'}}</span><br><span class="line">Student{id=4, name='小李', teacher=Teacher{id=1, name='曾老师'}}</span><br><span class="line">Student{id=5, name='小王', teacher=Teacher{id=1, name='曾老师'}}</span><br></pre></td></tr></tbody></table></figure><p><strong>总结：</strong></p><p>按照查询进行嵌套处理就像SQL中的子查询</p><p>按照结果进行嵌套处理就像SQL中的联表查询</p><blockquote><p>一对多处理</p></blockquote><p>module：mybatis-06</p><p>一个老师拥有多个学生</p><p>1、实体类编写</p><p>Student.java</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.pojo;</span><br><span class="line"><span class="comment">// pom.xml中引入lombok包，简化实体类的编写</span></span><br><span class="line"><span class="keyword">import</span> lombok.Data;</span><br><span class="line"></span><br><span class="line"><span class="meta">@Data</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Student</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">int</span> id;</span><br><span class="line">    <span class="keyword">private</span> String name;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">int</span> tid;</span><br><span class="line">}</span><br><span class="line"></span><br></pre></td></tr></tbody></table></figure><p>Teacher.java</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.pojo;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> lombok.Data;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> java.util.List;</span><br><span class="line"></span><br><span class="line"><span class="meta">@Data</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Teacher</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">int</span> id;</span><br><span class="line">    <span class="keyword">private</span> String name;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> List&lt;Student&gt; students;</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>和上述多对一一样，搭建测试环境！</p><blockquote><p>按结果嵌套查询</p></blockquote><p>1、TeacherMapper接口编写方法</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.dao;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> com.zzb.pojo.Teacher;</span><br><span class="line"><span class="keyword">import</span> org.apache.ibatis.annotations.Param;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">TeacherMapper</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 获取指定老师下的所有学生</span></span><br><span class="line">    <span class="function">Teacher <span class="title">getTeacher2</span><span class="params">(<span class="meta">@Param("tid")</span> <span class="keyword">int</span> id)</span></span>;</span><br><span class="line">}</span><br><span class="line"></span><br></pre></td></tr></tbody></table></figure><p>2、编写接口对应的Mapper配置文件</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8" ?&gt;</span></span><br><span class="line"><span class="meta">&lt;!DOCTYPE <span class="meta-keyword">mapper</span></span></span><br><span class="line"><span class="meta">        <span class="meta-keyword">PUBLIC</span> <span class="meta-string">"-//mybatis.org//DTD Config 3.0//EN"</span></span></span><br><span class="line"><span class="meta">        <span class="meta-string">"http://mybatis.org/dtd/mybatis-3-mapper.dtd"</span>&gt;</span></span><br><span class="line"><span class="comment">&lt;!--configuration--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">mapper</span> <span class="attr">namespace</span>=<span class="string">"com.zzb.dao.TeacherMapper"</span>&gt;</span></span><br><span class="line">    <span class="comment">&lt;!--按结果嵌套--&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getTeacher2"</span> <span class="attr">resultMap</span>=<span class="string">"TeacherStudent2"</span>&gt;</span></span><br><span class="line">    SELECT S.id AS sid, s.name AS sname, t.id AS tid, t.name AS tname</span><br><span class="line">    FROM student AS s, teacher AS t</span><br><span class="line">    WHERE s.tid = t.id;</span><br><span class="line">    <span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">resultMap</span> <span class="attr">id</span>=<span class="string">"TeacherStudent2"</span> <span class="attr">type</span>=<span class="string">"Teacher"</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">result</span> <span class="attr">property</span>=<span class="string">"id"</span> <span class="attr">column</span>=<span class="string">"tid"</span>/&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">result</span> <span class="attr">property</span>=<span class="string">"name"</span> <span class="attr">column</span>=<span class="string">"tname"</span>/&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">collection</span> <span class="attr">property</span>=<span class="string">"students"</span> <span class="attr">ofType</span>=<span class="string">"Student"</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">result</span> <span class="attr">property</span>=<span class="string">"id"</span> <span class="attr">column</span>=<span class="string">"sid"</span>/&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">result</span> <span class="attr">property</span>=<span class="string">"name"</span> <span class="attr">column</span>=<span class="string">"sname"</span>/&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">result</span> <span class="attr">property</span>=<span class="string">"tid"</span> <span class="attr">column</span>=<span class="string">"tid"</span>/&gt;</span></span><br><span class="line">        <span class="tag">&lt;/<span class="name">collection</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">resultMap</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">mapper</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>3、mybatis配置文件中注册mapper</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!--绑定接口--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">mappers</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">mapper</span> <span class="attr">class</span>=<span class="string">"com.zzb.dao.TeacherMapper"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">mappers</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>4、测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">getTeacher2</span><span class="params">()</span></span>{</span><br><span class="line">    SqlSession sqlSession = MybatisUtils.getSqlSession();</span><br><span class="line">    TeacherMapper mapper = sqlSession.getMapper(TeacherMapper.class);</span><br><span class="line">    Teacher teacher = mapper.getTeacher2(<span class="number">1</span>);</span><br><span class="line">    System.out.println(teacher);</span><br><span class="line"></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>测试结果：</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">Teacher(id=1, name=曾老师, students=[Student(id=1, name=小明, tid=1), Student(id=2, name=小红, tid=1), Student(id=3, name=小张, tid=1), Student(id=4, name=小李, tid=1), Student(id=5, name=小王, tid=1)])</span><br></pre></td></tr></tbody></table></figure><blockquote><p>按查询嵌套</p></blockquote><p>1、TeacherMapper接口编写方法</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 获取指定老师下的所有学生</span></span><br><span class="line"><span class="function">Teacher <span class="title">getTeacher</span><span class="params">(<span class="meta">@Param("tid")</span> <span class="keyword">int</span> id)</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>2、编写接口对应的Mapper配置文件</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!--按查询嵌套--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getTeacher"</span> <span class="attr">resultMap</span>=<span class="string">"TeacherStudent"</span>&gt;</span></span><br><span class="line">    select * from teacher</span><br><span class="line"><span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;<span class="name">resultMap</span> <span class="attr">id</span>=<span class="string">"TeacherStudent"</span> <span class="attr">type</span>=<span class="string">"teacher"</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">result</span> <span class="attr">property</span>=<span class="string">"id"</span> <span class="attr">column</span>=<span class="string">"id"</span>/&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">result</span> <span class="attr">property</span>=<span class="string">"name"</span> <span class="attr">column</span>=<span class="string">"name"</span>/&gt;</span></span><br><span class="line">    javatype是属性的类型 oftype是泛型的类型</span><br><span class="line">    <span class="tag">&lt;<span class="name">collection</span> <span class="attr">property</span>=<span class="string">"students"</span> <span class="attr">column</span>=<span class="string">"id"</span> <span class="attr">javaType</span>=<span class="string">"ArrayList"</span> <span class="attr">ofType</span>=<span class="string">"Student"</span> <span class="attr">select</span>=<span class="string">"getStudent"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">resultMap</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getStudent"</span> <span class="attr">resultType</span>=<span class="string">"Student"</span>&gt;</span></span><br><span class="line">    select * from student where tid = #{id}</span><br><span class="line"><span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>3、mybatis配置文件中注册mapper</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!--绑定接口--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">mappers</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">mapper</span> <span class="attr">class</span>=<span class="string">"com.zzb.dao.TeacherMapper"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">mappers</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>4、测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">getTeacher</span><span class="params">()</span></span>{</span><br><span class="line">    SqlSession sqlSession = MybatisUtils.getSqlSession();</span><br><span class="line"></span><br><span class="line">    TeacherMapper teacherMapper = sqlSession.getMapper(TeacherMapper.class);</span><br><span class="line">    Teacher teacher = teacherMapper.getTeacher(<span class="number">1</span>);</span><br><span class="line"></span><br><span class="line">    System.out.println(teacher);</span><br><span class="line"></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>测试结果：</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">Teacher(id=1, name=曾老师, students=[Student(id=1, name=小明, tid=1), Student(id=2, name=小红, tid=1), Student(id=3, name=小张, tid=1), Student(id=4, name=小李, tid=1), Student(id=5, name=小王, tid=1)])</span><br></pre></td></tr></tbody></table></figure><p><strong>总结：</strong></p><p>1、关联-association</p><p>2、集合-collection</p><p>3、所以association是用于一对一和多对一，而collection是用于一对多的关系</p><p>4、JavaType和ofType都是用来指定对象类型的</p><ul><li>JavaType是用来指定pojo中属性的类型</li><li>ofType指定的是映射到List集合属性中pojo的类型。</li></ul><p><strong>注意说明：</strong></p><p>1、保证SQL的可读性，尽量通俗易懂</p><p>2、根据实际要求，尽量编写性能更高的SQL语句</p><p>3、注意属性名和字段不一致的问题</p><p>4、注意一对多和多对一 中：字段和属性对应的问题</p><p>5、尽量使用Log4j，通过日志来查看自己的错误</p><h2 id="10-动态SQL"><a href="#10-动态SQL" class="headerlink" title="10 动态SQL"></a>10 动态SQL</h2><blockquote><p>介绍</p></blockquote><p>==什么是动态SQL？==</p><p><strong>动态SQL指的是根据不同的查询条件 , 生成不同的Sql语句。</strong></p><blockquote><p>官网描述：<br>MyBatis 的强大特性之一便是它的动态 SQL。如果你有使用 JDBC 或其它类似框架的经验，你就能体会到根据不同条件拼接 SQL 语句的痛苦。例如拼接时要确保不能忘记添加必要的空格，还要注意去掉列表最后一个列名的逗号。利用动态 SQL 这一特性可以彻底摆脱这种痛苦。<br>虽然在以前使用动态 SQL 并非一件易事，但正是 MyBatis 提供了可以被用在任意 SQL 映射语句中的强大的动态 SQL 语言得以改进这种情形。<br>动态 SQL 元素和 JSTL 或基于类似 XML 的文本处理器相似。在 MyBatis 之前的版本中，有很多元素需要花时间了解。MyBatis 3 大大精简了元素种类，现在只需学习原来一半的元素便可。MyBatis 采用功能强大的基于 OGNL 的表达式来淘汰其它大部分元素。</p><hr><ul><li>if</li><li>choose (when, otherwise)</li><li>trim (where, set)</li><li>foreach</li></ul><hr></blockquote><p>我们之前写的 SQL 语句都比较简单，如果有比较复杂的业务，我们需要写复杂的 SQL 语句，往往需要拼接，而拼接 SQL ，稍微不注意，由于引号，空格等缺失可能都会导致错误。</p><p>那么怎么去解决这个问题呢？这就要使用 mybatis 动态SQL，通过 if, choose, when, otherwise, trim, where, set, foreach等标签，可组合成非常灵活的SQL语句，从而在提高 SQL 语句的准确性的同时，也大大提高了开发人员的效率。</p><blockquote><p>搭建环境</p></blockquote><p>在mybatis数据库中新建一个表：blog</p><figure class="highlight sql"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">CREATE</span> <span class="keyword">TABLE</span> `blog` (</span><br><span class="line">`id` <span class="type">varchar</span>(<span class="number">50</span>) <span class="keyword">NOT</span> <span class="keyword">NULL</span> COMMENT <span class="string">'博客id'</span>,</span><br><span class="line">`title` <span class="type">varchar</span>(<span class="number">100</span>) <span class="keyword">NOT</span> <span class="keyword">NULL</span> COMMENT <span class="string">'博客标题'</span>,</span><br><span class="line">`author` <span class="type">varchar</span>(<span class="number">30</span>) <span class="keyword">NOT</span> <span class="keyword">NULL</span> COMMENT <span class="string">'博客作者'</span>,</span><br><span class="line">`create_time` datetime <span class="keyword">NOT</span> <span class="keyword">NULL</span> COMMENT <span class="string">'创建时间'</span>,</span><br><span class="line">`views` <span class="type">int</span>(<span class="number">30</span>) <span class="keyword">NOT</span> <span class="keyword">NULL</span> COMMENT <span class="string">'浏览量'</span></span><br><span class="line">) ENGINE<span class="operator">=</span>InnoDB <span class="keyword">DEFAULT</span> CHARSET<span class="operator">=</span>utf8</span><br></pre></td></tr></tbody></table></figure><p>1、创建Mybatis基础工程，module：mybatis-07</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201210202134351.png" alt="image-20201210202134351"></p><p>2、IDUtil 工具类</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.utils;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> java.util.UUID;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">IDUtil</span> </span>{</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> String <span class="title">getId</span><span class="params">()</span></span>{</span><br><span class="line">        <span class="keyword">return</span> UUID.randomUUID().toString().replaceAll(<span class="string">"-"</span>,<span class="string">""</span>);</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>3、编写实体类Blog</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.pojo;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> java.util.Date;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Blog</span> </span>{</span><br><span class="line">    <span class="keyword">private</span> String id;</span><br><span class="line">    <span class="keyword">private</span> String title;</span><br><span class="line">    <span class="keyword">private</span> String author;</span><br><span class="line">    <span class="keyword">private</span> Date createTime;</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">int</span> views;</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="title">Blog</span><span class="params">()</span> </span>{</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="title">Blog</span><span class="params">(String id, String title, String author, Date createTime, <span class="keyword">int</span> views)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.id = id;</span><br><span class="line">        <span class="keyword">this</span>.title = title;</span><br><span class="line">        <span class="keyword">this</span>.author = author;</span><br><span class="line">        <span class="keyword">this</span>.createTime = createTime;</span><br><span class="line">        <span class="keyword">this</span>.views = views;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">getId</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> id;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setId</span><span class="params">(String id)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.id = id;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">getTitle</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> title;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setTitle</span><span class="params">(String title)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.title = title;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">getAuthor</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> author;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setAuthor</span><span class="params">(String author)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.author = author;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> Date <span class="title">getCreateTime</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> createTime;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setCreateTime</span><span class="params">(Date createTime)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.createTime = createTime;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">getViews</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> views;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">setViews</span><span class="params">(<span class="keyword">int</span> views)</span> </span>{</span><br><span class="line">        <span class="keyword">this</span>.views = views;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">toString</span><span class="params">()</span> </span>{</span><br><span class="line">        <span class="keyword">return</span> <span class="string">"Blog{"</span> +</span><br><span class="line">                <span class="string">"id='"</span> + id + <span class="string">'\''</span> +</span><br><span class="line">                <span class="string">", title='"</span> + title + <span class="string">'\''</span> +</span><br><span class="line">                <span class="string">", author='"</span> + author + <span class="string">'\''</span> +</span><br><span class="line">                <span class="string">", createTime="</span> + createTime +</span><br><span class="line">                <span class="string">", views="</span> + views +</span><br><span class="line">                <span class="string">'}'</span>;</span><br><span class="line">    }</span><br><span class="line">}</span><br><span class="line"></span><br></pre></td></tr></tbody></table></figure><p>4、编写Mapper接口及xml配置文件</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">BlogMapper</span> </span>{</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8" ?&gt;</span></span><br><span class="line"><span class="meta">&lt;!DOCTYPE <span class="meta-keyword">mapper</span></span></span><br><span class="line"><span class="meta">       <span class="meta-keyword">PUBLIC</span> <span class="meta-string">"-//mybatis.org//DTD Mapper 3.0//EN"</span></span></span><br><span class="line"><span class="meta">       <span class="meta-string">"http://mybatis.org/dtd/mybatis-3-mapper.dtd"</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">mapper</span> <span class="attr">namespace</span>=<span class="string">"com.zzb.mapper.BlogMapper"</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">mapper</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>5、编写mybatis核心配置文件，注册mapper、下划线驼峰自动转换以及日志输出格式</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">settings</span>&gt;</span></span><br><span class="line">   <span class="tag">&lt;<span class="name">setting</span> <span class="attr">name</span>=<span class="string">"mapUnderscoreToCamelCase"</span> <span class="attr">value</span>=<span class="string">"true"</span>/&gt;</span></span><br><span class="line">   <span class="tag">&lt;<span class="name">setting</span> <span class="attr">name</span>=<span class="string">"logImpl"</span> <span class="attr">value</span>=<span class="string">"STDOUT_LOGGING"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">settings</span>&gt;</span></span><br><span class="line"><span class="comment">&lt;!--注册Mapper.xml--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">mappers</span>&gt;</span></span><br><span class="line"> <span class="tag">&lt;<span class="name">mapper</span> <span class="attr">resource</span>=<span class="string">"mapper/BlogMapper.xml"</span>/&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">mappers</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>6、插入初始数据</p><p>编写接口方法</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 新增一个博客</span></span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">addBlog</span><span class="params">(Blog blog)</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>BlogMapper.xml配置文件编写</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">insert</span> <span class="attr">id</span>=<span class="string">"addBlog"</span> <span class="attr">parameterType</span>=<span class="string">"Blog"</span>&gt;</span></span><br><span class="line">    insert into blog (id, title, author, create_time, views) values (#{id}, #{title}, #{author}, #{createTime}, #{views})</span><br><span class="line"><span class="tag">&lt;/<span class="name">insert</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>测试，插入博客数据:</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">addBlog</span><span class="params">()</span></span>{</span><br><span class="line"></span><br><span class="line">    SqlSession sqlSession = MybatisUtils.getSqlSession();</span><br><span class="line">    BlogMapper mapper = sqlSession.getMapper(BlogMapper.class);</span><br><span class="line"></span><br><span class="line">    Blog blog = <span class="keyword">new</span> Blog();</span><br><span class="line">    blog.setId(IDUtil.getId());</span><br><span class="line">    blog.setTitle(<span class="string">"Mybatis如此简单"</span>);</span><br><span class="line">    blog.setAuthor(<span class="string">"ZZB"</span>);</span><br><span class="line">    blog.setCreateTime(<span class="keyword">new</span> Date());</span><br><span class="line">    blog.setViews(<span class="number">9999</span>);</span><br><span class="line"></span><br><span class="line">    mapper.addBlog(blog);</span><br><span class="line"></span><br><span class="line">    blog.setId(IDUtil.getId());</span><br><span class="line">    blog.setTitle(<span class="string">"Java如此简单"</span>);</span><br><span class="line">    mapper.addBlog(blog);</span><br><span class="line"></span><br><span class="line">    blog.setId(IDUtil.getId());</span><br><span class="line">    blog.setTitle(<span class="string">"Spring如此简单"</span>);</span><br><span class="line">    mapper.addBlog(blog);</span><br><span class="line"></span><br><span class="line">    blog.setId(IDUtil.getId());</span><br><span class="line">    blog.setTitle(<span class="string">"微服务如此简单"</span>);</span><br><span class="line">    mapper.addBlog(blog);</span><br><span class="line"></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>初始化数据完毕！</p><p>测试结果：</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201210202941177.png" alt="image-20201210202941177"></p><blockquote><p>if </p></blockquote><p><strong>需求：根据作者名字和博客名字来查询博客！如果作者名字为空，那么只根据博客名字查询，反之，则根据作者名来查询</strong></p><p>1、编写接口类</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 查询博客</span></span><br><span class="line"><span class="function">List&lt;Blog&gt; <span class="title">queryBlogByIf</span><span class="params">(Map map)</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>2、编写BlogMapper.xml文件</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">sql</span> <span class="attr">id</span>=<span class="string">"if-title-author"</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">if</span> <span class="attr">test</span>=<span class="string">"title != null"</span>&gt;</span></span><br><span class="line">        title = #{title}</span><br><span class="line">    <span class="tag">&lt;/<span class="name">if</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">if</span> <span class="attr">test</span>=<span class="string">"author != null"</span>&gt;</span></span><br><span class="line">        and author = #{author}</span><br><span class="line">    <span class="tag">&lt;/<span class="name">if</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">sql</span>&gt;</span></span><br><span class="line"><span class="comment">&lt;!--需求1：</span></span><br><span class="line"><span class="comment">根据作者名字和博客名字来查询博客！</span></span><br><span class="line"><span class="comment">如果作者名字为空，那么只根据博客名字查询，反之，则根据作者名来查询</span></span><br><span class="line"><span class="comment">select * from blog where title = #{title} and author = #{author}</span></span><br><span class="line"><span class="comment">--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"queryBlogByIf"</span> <span class="attr">parameterType</span>=<span class="string">"map"</span> <span class="attr">resultType</span>=<span class="string">"Blog"</span>&gt;</span></span><br><span class="line">    select * from blog</span><br><span class="line">    <span class="tag">&lt;<span class="name">where</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">include</span> <span class="attr">refid</span>=<span class="string">"if-title-author"</span>&gt;</span><span class="tag">&lt;/<span class="name">include</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">where</span>&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>3、测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">queryBlogByIf</span><span class="params">()</span></span>{</span><br><span class="line"></span><br><span class="line">    SqlSession sqlSession = MybatisUtils.getSqlSession();</span><br><span class="line"></span><br><span class="line">    BlogMapper mapper = sqlSession.getMapper(BlogMapper.class);</span><br><span class="line">    Map map = <span class="keyword">new</span> HashMap();</span><br><span class="line">    map.put(<span class="string">"title"</span>, <span class="string">"Java如此简单"</span>);</span><br><span class="line">    map.put(<span class="string">"author"</span>, <span class="string">"ZZB"</span>);</span><br><span class="line"></span><br><span class="line">    List&lt;Blog&gt; blogs = mapper.queryBlogByIf(map);</span><br><span class="line">    <span class="keyword">for</span> (Blog blog : blogs) {</span><br><span class="line">        System.out.println(blog);</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>测试结果：</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">Blog{id='01a7d83785c8483cae5d5384772f5c68', title='Java如此简单', author='ZZB', createTime=Thu Dec 10 20:29:03 CST 2020, views=9999}</span><br></pre></td></tr></tbody></table></figure><p>这个“where”标签会知道如果它包含的标签中有返回值的话，它就插入一个‘where’。此外，如果标签返回的内容是以AND 或OR 开头的，则它会剔除掉。</p><blockquote><p>Set</p></blockquote><p><strong>需求：更新一个博客</strong></p><p>1、编写接口方法</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 更新一个博客</span></span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">updateBlog</span><span class="params">(Map map)</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>2、编写BlogMapper.xml配置文件</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">update</span> <span class="attr">id</span>=<span class="string">"updateBlog"</span> <span class="attr">parameterType</span>=<span class="string">"map"</span>&gt;</span></span><br><span class="line">    update blog</span><br><span class="line">    <span class="tag">&lt;<span class="name">set</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">if</span> <span class="attr">test</span>=<span class="string">"title != null"</span>&gt;</span></span><br><span class="line">            title = #{title},</span><br><span class="line">        <span class="tag">&lt;/<span class="name">if</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">if</span> <span class="attr">test</span>=<span class="string">"author != null"</span>&gt;</span></span><br><span class="line">            author = #{author}</span><br><span class="line">        <span class="tag">&lt;/<span class="name">if</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">set</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">where</span>&gt;</span></span><br><span class="line">        id = #{id}</span><br><span class="line">    <span class="tag">&lt;/<span class="name">where</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">update</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>3、测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">updateBlog</span><span class="params">()</span></span>{</span><br><span class="line"></span><br><span class="line">    SqlSession sqlSession = MybatisUtils.getSqlSession();</span><br><span class="line"></span><br><span class="line">    BlogMapper mapper = sqlSession.getMapper(BlogMapper.class);</span><br><span class="line">    Map map = <span class="keyword">new</span> HashMap();</span><br><span class="line">    map.put(<span class="string">"title"</span>, <span class="string">"Java如此简单2"</span>);</span><br><span class="line">    map.put(<span class="string">"author"</span>, <span class="string">"zb"</span>);</span><br><span class="line">    map.put(<span class="string">"id"</span>, <span class="string">"01a7d83785c8483cae5d5384772f5c68"</span>);</span><br><span class="line"></span><br><span class="line">    mapper.updateBlog(map);</span><br><span class="line"></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>测试结果：</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201210204512899.png" alt="image-20201210204512899"></p><blockquote><p>choose</p></blockquote><p>有时候，我们不想用到所有的查询条件，只想选择其中的一个，查询条件有一个满足即可，使用 choose 标签可以解决此类问题，类似于 Java 的 switch 语句</p><p>1、编写接口方法</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="function">List&lt;Blog&gt; <span class="title">queryBlogByChoose</span><span class="params">(Map map)</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>2、编写BlogMapper.xml配置文件</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"queryBlogByChoose"</span> <span class="attr">parameterType</span>=<span class="string">"map"</span> <span class="attr">resultType</span>=<span class="string">"Blog"</span>&gt;</span></span><br><span class="line">    select * from blog</span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">where</span>&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">choose</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">when</span> <span class="attr">test</span>=<span class="string">"title != null"</span>&gt;</span></span><br><span class="line">                title = #{title}</span><br><span class="line">            <span class="tag">&lt;/<span class="name">when</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">when</span> <span class="attr">test</span>=<span class="string">"author != null "</span>&gt;</span></span><br><span class="line">                author = #{author}</span><br><span class="line">            <span class="tag">&lt;/<span class="name">when</span>&gt;</span></span><br><span class="line">            <span class="tag">&lt;<span class="name">otherwise</span>&gt;</span></span><br><span class="line">                views = #{views}</span><br><span class="line">            <span class="tag">&lt;/<span class="name">otherwise</span>&gt;</span></span><br><span class="line"></span><br><span class="line">        <span class="tag">&lt;/<span class="name">choose</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">where</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>3、测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">queryBlogByChoose</span><span class="params">()</span></span>{</span><br><span class="line"></span><br><span class="line">    SqlSession sqlSession = MybatisUtils.getSqlSession();</span><br><span class="line"></span><br><span class="line">    BlogMapper mapper = sqlSession.getMapper(BlogMapper.class);</span><br><span class="line">    Map map = <span class="keyword">new</span> HashMap();</span><br><span class="line">    map.put(<span class="string">"title"</span>, <span class="string">"Java如此简单2"</span>);</span><br><span class="line">    map.put(<span class="string">"author"</span>, <span class="string">"ZZB"</span>);</span><br><span class="line"></span><br><span class="line">    List&lt;Blog&gt; blogs = mapper.queryBlogByChoose(map);</span><br><span class="line">    <span class="keyword">for</span> (Blog blog : blogs) {</span><br><span class="line">        System.out.println(blog);</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>测试结果：</p><p>注意SQL语句</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201210204946348.png" alt="image-20201210204946348"></p><blockquote><p>SQL片段</p></blockquote><p>有时候可能某个 sql 语句我们用的特别多，为了增加代码的重用性，简化代码，我们需要将这些代码抽取出来，然后使用时直接调用。</p><p><strong>提取SQL片段：</strong></p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">sql</span> <span class="attr">id</span>=<span class="string">"if-title-author"</span>&gt;</span></span><br><span class="line">   <span class="tag">&lt;<span class="name">if</span> <span class="attr">test</span>=<span class="string">"title != null"</span>&gt;</span></span><br><span class="line">      title = #{title}</span><br><span class="line">   <span class="tag">&lt;/<span class="name">if</span>&gt;</span></span><br><span class="line">   <span class="tag">&lt;<span class="name">if</span> <span class="attr">test</span>=<span class="string">"author != null"</span>&gt;</span></span><br><span class="line">      and author = #{author}</span><br><span class="line">   <span class="tag">&lt;/<span class="name">if</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">sql</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p><strong>引用SQL片段：</strong></p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"queryBlogIf"</span> <span class="attr">parameterType</span>=<span class="string">"map"</span> <span class="attr">resultType</span>=<span class="string">"blog"</span>&gt;</span></span><br><span class="line">  select * from blog</span><br><span class="line">   <span class="tag">&lt;<span class="name">where</span>&gt;</span></span><br><span class="line">       <span class="comment">&lt;!-- 引用 sql 片段，如果refid 指定的不在本文件中，那么需要在前面加上 namespace --&gt;</span></span><br><span class="line">       <span class="tag">&lt;<span class="name">include</span> <span class="attr">refid</span>=<span class="string">"if-title-author"</span>&gt;</span><span class="tag">&lt;/<span class="name">include</span>&gt;</span></span><br><span class="line">       <span class="comment">&lt;!-- 在这里还可以引用其他的 sql 片段 --&gt;</span></span><br><span class="line">   <span class="tag">&lt;/<span class="name">where</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>注意：</p><p>1、最好基于 单表来定义 sql 片段，提高片段的可重用性；</p><p>2、在 sql 片段中不要包括 where。</p><blockquote><p>ForEach</p></blockquote><p>首先将数据库中的表格id修改为1，2，3，4</p><p><strong>需求：查询 id 分别为1，3，4 的博客信息</strong></p><p>1、编写接口方法</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// ForEach</span></span><br><span class="line"><span class="function">List&lt;Blog&gt; <span class="title">queryBlogForeach</span><span class="params">(Map map)</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>2、编写BlogMapper.xml配置文件</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"queryBlogForeach"</span> <span class="attr">parameterType</span>=<span class="string">"map"</span> <span class="attr">resultType</span>=<span class="string">"blog"</span>&gt;</span></span><br><span class="line">    select * from blog</span><br><span class="line">    <span class="tag">&lt;<span class="name">where</span>&gt;</span></span><br><span class="line">   <span class="comment">&lt;!--</span></span><br><span class="line"><span class="comment">       collection:指定输入对象中的集合属性</span></span><br><span class="line"><span class="comment">       item:每次遍历生成的对象</span></span><br><span class="line"><span class="comment">       open:开始遍历时的拼接字符串</span></span><br><span class="line"><span class="comment">       close:结束时拼接的字符串</span></span><br><span class="line"><span class="comment">       separator:遍历对象之间需要拼接的字符串</span></span><br><span class="line"><span class="comment"> --&gt;</span></span><br><span class="line">        <span class="tag">&lt;<span class="name">foreach</span> <span class="attr">collection</span>=<span class="string">"ids"</span> <span class="attr">item</span>=<span class="string">"id"</span> <span class="attr">open</span>=<span class="string">"and ("</span> <span class="attr">close</span>=<span class="string">")"</span> <span class="attr">separator</span>=<span class="string">"or"</span>&gt;</span></span><br><span class="line">            id = #{id}</span><br><span class="line">        <span class="tag">&lt;/<span class="name">foreach</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;/<span class="name">where</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>3、测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">queryBlogForeach</span><span class="params">()</span></span>{</span><br><span class="line">    SqlSession sqlSession = MybatisUtils.getSqlSession();</span><br><span class="line">    BlogMapper mapper = sqlSession.getMapper(BlogMapper.class);</span><br><span class="line">    Map map = <span class="keyword">new</span> HashMap();</span><br><span class="line">    List&lt;Integer&gt; ids = <span class="keyword">new</span> ArrayList&lt;Integer&gt;();</span><br><span class="line">    ids.add(<span class="number">1</span>);</span><br><span class="line">    ids.add(<span class="number">3</span>);</span><br><span class="line">    ids.add(<span class="number">4</span>);</span><br><span class="line"></span><br><span class="line">    map.put(<span class="string">"ids"</span>, ids);</span><br><span class="line">    List&lt;Blog&gt; blogList = mapper.queryBlogForeach(map);</span><br><span class="line">    <span class="keyword">for</span> (Blog blog : blogList) {</span><br><span class="line">        System.out.println(blog);</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>测试结果：</p><p>注意SQL语句</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201210210021528.png" alt="image-20201210210021528"></p><p><strong>总结：</strong></p><p>==其实动态 sql 语句的编写往往就是一个拼接的问题，为了保证拼接准确，我们最好首先要写原生的 sql 语句出来，然后在通过 mybatis 动态sql 对照着改，防止出错。多在实践中使用才是熟练掌握它的技巧==</p><p>建议：</p><p>先在mysql写出完整的sql，再对应的修改为动态的sql</p><h2 id="11-缓存"><a href="#11-缓存" class="headerlink" title="11 缓存"></a>11 缓存</h2><blockquote><p>简介</p></blockquote><p>1、什么是缓存 [ Cache ] ?</p><ul><li>存在内存中的临时数据</li><li>将用户经常查询的数据存放在缓存中（内存），用户去查询数据就不用从磁盘上（关系型数据库文件）查询，从缓存中直接查询，从而提高查询效率，解决了高并发系统的性能问题。</li></ul><p>2、为什么使用缓存？</p><ul><li>减少和数据库的交互次数，减少系统的开销，提高系统的效率。</li></ul><p>3、什么样的数据能使用缓存？</p><ul><li>经常查询并且不经常改变的数据。</li></ul><blockquote><p>MyBatis缓存</p></blockquote><ul><li><p>MyBatis包含一个非常强大的查询缓存特性，它可以非常方便地定制和配置缓存。缓存可以极大的提升查询效率。  </p></li><li><p>MyBatis系统中默认定义了两级缓存：<strong>一级缓存</strong>和<strong>二级缓存</strong></p></li><li><ul><li>默认情况下，只有一级缓存开启。（SqlSession级别的缓存，也称为本地缓存）</li><li>二级缓存需要手动开启和配置，他是基于namespace级别的缓存。</li><li>为了提高扩展性，MyBatis定义了缓存接口Cache。我们可以通过实现Cache接口来自定义二级缓存</li></ul></li></ul><blockquote><p>一级缓存</p></blockquote><p>一级缓存也叫本地缓存：</p><ul><li>与数据库同一次会话期间查询到的数据会放在本地缓存中；</li><li>以后如果需要获取相同的数据，直接从缓存中拿，没必须再去查询数据库。</li></ul><blockquote><p>测试</p></blockquote><p>module：mybatis-08</p><p>1、在MyBatis核心配置文件中加入日志，方便测试结果的查看。</p><p>2、编写实体类User.java</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.pojo;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> lombok.AllArgsConstructor;</span><br><span class="line"><span class="keyword">import</span> lombok.Data;</span><br><span class="line"><span class="keyword">import</span> lombok.NoArgsConstructor;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> java.io.Serializable;</span><br><span class="line"></span><br><span class="line"><span class="meta">@Data</span></span><br><span class="line"><span class="meta">@AllArgsConstructor</span></span><br><span class="line"><span class="meta">@NoArgsConstructor</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">User</span> <span class="keyword">implements</span> <span class="title">Serializable</span> </span>{</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">int</span> id;</span><br><span class="line">    <span class="keyword">private</span> String name;</span><br><span class="line">    <span class="keyword">private</span> String pwd;</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>3、编写UserMapper接口</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.zzb.dao;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> com.zzb.pojo.User;</span><br><span class="line"><span class="keyword">import</span> org.apache.ibatis.annotations.Param;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">UserMapper</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 根据Id查询用户</span></span><br><span class="line">    <span class="function">User <span class="title">getUserById</span><span class="params">(<span class="meta">@Param("id")</span> <span class="keyword">int</span> id)</span></span>;</span><br><span class="line">}</span><br><span class="line"></span><br></pre></td></tr></tbody></table></figure><p>4、编写UserMapper.xml配置文件</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8" ?&gt;</span></span><br><span class="line"><span class="meta">&lt;!DOCTYPE <span class="meta-keyword">mapper</span></span></span><br><span class="line"><span class="meta">        <span class="meta-keyword">PUBLIC</span> <span class="meta-string">"-//mybatis.org//DTD Config 3.0//EN"</span></span></span><br><span class="line"><span class="meta">        <span class="meta-string">"http://mybatis.org/dtd/mybatis-3-mapper.dtd"</span>&gt;</span></span><br><span class="line"><span class="comment">&lt;!--configuration--&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">mapper</span> <span class="attr">namespace</span>=<span class="string">"com.zzb.dao.UserMapper"</span>&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">cache</span>/&gt;</span></span><br><span class="line"></span><br><span class="line">    <span class="tag">&lt;<span class="name">select</span> <span class="attr">id</span>=<span class="string">"getUserById"</span> <span class="attr">resultType</span>=<span class="string">"User"</span>&gt;</span></span><br><span class="line">        select * from user where id = #{id}</span><br><span class="line">    <span class="tag">&lt;/<span class="name">select</span>&gt;</span></span><br><span class="line"></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">mapper</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>5、测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">test2</span><span class="params">()</span></span>{</span><br><span class="line">    SqlSession sqlSession = MybatisUtils.getSqlSession();</span><br><span class="line">    UserMapper userMapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line"></span><br><span class="line">    User user = userMapper.getUserById(<span class="number">1</span>);</span><br><span class="line">    System.out.println(user);</span><br><span class="line">    User user2 = userMapper.getUserById(<span class="number">1</span>);</span><br><span class="line">    System.out.println(user == user2);</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">    sqlSession.close();</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>测试结果：</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201210212931401.png" alt="image-20201210212931401"></p><p>很显然，测试仅从数据库中查询了一次，并将结果存入了缓存中。</p><blockquote><p>一级缓存失效的四种情况</p></blockquote><p>一级缓存是SqlSession级别的缓存，是一直开启的，我们关闭不了它；</p><p>一级缓存失效情况：没有使用到当前的一级缓存，那么还需要再向数据库中发起一次查询请求！</p><p>1、SqlSession不同</p><p>测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">test</span><span class="params">()</span></span>{</span><br><span class="line">    SqlSession sqlSession = MybatisUtils.getSqlSession();</span><br><span class="line">    SqlSession sqlSession2 = MybatisUtils.getSqlSession();</span><br><span class="line">    UserMapper userMapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line">    UserMapper userMapper2 = sqlSession2.getMapper(UserMapper.class);</span><br><span class="line"></span><br><span class="line">    User user = userMapper.getUserById(<span class="number">1</span>);</span><br><span class="line">    System.out.println(user);</span><br><span class="line"></span><br><span class="line">    User user2 = userMapper2.getUserById(<span class="number">1</span>);</span><br><span class="line">    System.out.println(user2);</span><br><span class="line"></span><br><span class="line">    System.out.println(user == user2);</span><br><span class="line"></span><br><span class="line">    sqlSession.close();</span><br><span class="line">    sqlSession2.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>测试结果：</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201210213236283.png" alt="image-20201210213236283"></p><p>测试结果中执行了两次SQL语句，表明<strong>每个SqlSession中的缓存相互独立！</strong></p><p>2、SqlSession相同，查询条件不同</p><p>测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">test2</span><span class="params">()</span></span>{</span><br><span class="line">    SqlSession sqlSession = MybatisUtils.getSqlSession();</span><br><span class="line">    UserMapper userMapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line"></span><br><span class="line">    User user = userMapper.getUserById(<span class="number">1</span>);</span><br><span class="line">    System.out.println(user);</span><br><span class="line">    User user2 = userMapper.getUserById(<span class="number">2</span>);</span><br><span class="line">    System.out.println(user == user2);</span><br><span class="line">    </span><br><span class="line">    sqlSession.close();</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>测试结果：</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201210213508832.png" alt="image-20201210213508832"></p><p>两个SQL语句不同，查询结果不同，故不会从一级缓存中命中结果！</p><p>3、SqlSession相同，但两次查询之间执行了增删改操作！</p><p>UserMapper接口中增加方法：</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 修改一个用户</span></span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">updateUser</span><span class="params">(Map map)</span></span>;</span><br></pre></td></tr></tbody></table></figure><p>UserMapper.xml编写：</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">update</span> <span class="attr">id</span>=<span class="string">"updateUser"</span> <span class="attr">parameterType</span>=<span class="string">"map"</span>&gt;</span></span><br><span class="line">    update user set name = #{name} where id = #{id}</span><br><span class="line"><span class="tag">&lt;/<span class="name">update</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">test3</span><span class="params">()</span></span>{</span><br><span class="line">    SqlSession sqlSession = MybatisUtils.getSqlSession();</span><br><span class="line">    UserMapper userMapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line"></span><br><span class="line">    User user1 = userMapper.getUserById(<span class="number">1</span>);</span><br><span class="line">    System.out.println(user1);</span><br><span class="line"></span><br><span class="line">    Map&lt;Object, Object&gt; map = <span class="keyword">new</span> HashMap&lt;Object, Object&gt;();</span><br><span class="line">    map.put(<span class="string">"name"</span>, <span class="string">"zb"</span>);</span><br><span class="line">    map.put(<span class="string">"id"</span>, <span class="number">4</span>);</span><br><span class="line">    <span class="keyword">int</span> i = userMapper.updateUser(map);</span><br><span class="line">    <span class="keyword">if</span>(i == <span class="number">1</span>){</span><br><span class="line">        System.out.println(<span class="string">"修改数据成功！"</span>);</span><br><span class="line">    }<span class="keyword">else</span>{</span><br><span class="line">        System.out.println(<span class="string">"修改数据失败！"</span>);</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">    User user2 = userMapper.getUserById(<span class="number">1</span>);</span><br><span class="line">    System.out.println(user2);</span><br><span class="line"></span><br><span class="line">    System.out.println(user1 == user2);</span><br><span class="line"></span><br><span class="line">    sqlSession.close();</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>测试结果:</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201210214315828.png" alt="image-20201210214315828"></p><p>测试结果表明，两次查询间如果执行了增删改方法，一级缓存会被清空！<strong>因为增删改操作可能会对当前数据产生影响！</strong></p><p>4、SqlSession相同，手动清除一级缓存</p><p>测试</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">test2</span><span class="params">()</span></span>{</span><br><span class="line">    SqlSession sqlSession = MybatisUtils.getSqlSession();</span><br><span class="line">    UserMapper userMapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line"></span><br><span class="line">    User user = userMapper.getUserById(<span class="number">1</span>);</span><br><span class="line">    System.out.println(user);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 手动清除一级缓存</span></span><br><span class="line">    sqlSession.clearCache();</span><br><span class="line"></span><br><span class="line">    User user2 = userMapper.getUserById(<span class="number">1</span>);</span><br><span class="line">    System.out.println(user == user2);</span><br><span class="line"></span><br><span class="line">    sqlSession.close();</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>测试结果：</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201210214648807.png" alt="image-20201210214648807"></p><blockquote><p>二级缓存</p></blockquote><ul><li><p>二级缓存也叫全局缓存，一级缓存作用域太低了，所以诞生了二级缓存</p></li><li><p>基于namespace级别的缓存，一个名称空间，对应一个二级缓存；</p></li><li><p>工作机制</p></li><li><ul><li>一个会话查询一条数据，这个数据就会被放在当前会话的一级缓存中；</li><li>如果当前会话关闭了，这个会话对应的一级缓存就没了；但是我们想要的是，会话关闭了，一级缓存中的数据被保存到二级缓存中；</li><li>新的会话查询信息，就可以从二级缓存中获取内容；</li><li>不同的mapper查出的数据会放在自己对应的缓存（map）中；</li></ul></li></ul><blockquote><p>使用步骤</p></blockquote><p>1、开启全局缓存</p><p>在mybatis核心配置文件中添加如下配置：</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">setting</span> <span class="attr">name</span>=<span class="string">"cacheEnabled"</span> <span class="attr">value</span>=<span class="string">"true"</span>/&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>2、在每一个Mapper.xml配置文件中使用二级缓存</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">cache</span>/&gt;</span></span><br><span class="line"></span><br><span class="line">官方示例=====&gt;查看官方文档</span><br><span class="line">&lt;cache</span><br><span class="line"> eviction="FIFO"</span><br><span class="line"> flushInterval="60000"</span><br><span class="line"> size="512"</span><br><span class="line"> readOnly="true"/&gt;</span><br><span class="line">这个更高级的配置创建了一个 FIFO 缓存，每隔 60 秒刷新，最多可以存储结果对象或列表的 512 个引用，而且返回的对象被认为是只读的，因此对它们进行修改可能会在不同线程中的调用者产生冲突。</span><br></pre></td></tr></tbody></table></figure><p>3、代码测试</p><p><strong>所有实体类先实现序列化接口。</strong></p><p>测试代码：</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line">  <span class="meta">@Test</span></span><br><span class="line">  <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">test</span><span class="params">()</span></span>{</span><br><span class="line">      SqlSession sqlSession = MybatisUtils.getSqlSession();</span><br><span class="line">      SqlSession sqlSession2 = MybatisUtils.getSqlSession();</span><br><span class="line">      UserMapper userMapper = sqlSession.getMapper(UserMapper.class);</span><br><span class="line">      UserMapper userMapper2 = sqlSession2.getMapper(UserMapper.class);</span><br><span class="line"></span><br><span class="line">      User user = userMapper.getUserById(<span class="number">1</span>);</span><br><span class="line">      System.out.println(user);</span><br><span class="line"><span class="comment">// 关闭sqlSession，是该sqlSession中的一级缓存的内容存放到二级缓存中</span></span><br><span class="line">      sqlSession.close();</span><br><span class="line"></span><br><span class="line">      User user2 = userMapper2.getUserById(<span class="number">1</span>);</span><br><span class="line">      System.out.println(user2);</span><br><span class="line"></span><br><span class="line">      System.out.println(user == user2);</span><br><span class="line"></span><br><span class="line">      sqlSession.close();</span><br><span class="line">      sqlSession2.close();</span><br><span class="line">  }</span><br></pre></td></tr></tbody></table></figure><p>测试结果：</p><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201210215634682.png" alt="image-20201210215634682"></p><ul><li>只要开启了二级缓存，我们在同一个Mapper中的查询，可以在二级缓存中拿到数据</li><li>查出的数据都会被默认先放在一级缓存中</li><li>只有会话提交或者关闭以后，一级缓存中的数据才会转到二级缓存中</li></ul><blockquote><p>缓存原理图</p></blockquote><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201210220100854.png" alt="image-20201210220100854"></p><blockquote><p>EhCache</p></blockquote><p><img src="https://gitee.com/zzb9527/blog-image/raw/master/img/image-20201210220223892.png" alt="image-20201210220223892"></p><p>第三方缓存实现–EhCache;</p><p>Ehcache是一种广泛使用的java分布式缓存，用于通用缓存；</p><p>要在应用程序中使用Ehcache，需要引入依赖的jar包：</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!-- https://mvnrepository.com/artifact/org.mybatis.caches/mybatis-ehcache --&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">   <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>org.mybatis.caches<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">   <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>mybatis-ehcache<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">   <span class="tag">&lt;<span class="name">version</span>&gt;</span>1.1.0<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>在mapper.xml中使用对应的缓存即可</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">mapper</span> <span class="attr">namespace</span> = <span class="string">“org.acme.FooMapper”</span> &gt;</span> </span><br><span class="line">   <span class="tag">&lt;<span class="name">cache</span> <span class="attr">type</span> = <span class="string">“org.mybatis.caches.ehcache.EhcacheCache”</span> /&gt;</span> </span><br><span class="line"><span class="tag">&lt;/<span class="name">mapper</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure><p>编写ehcache.xml文件，如果在加载时未找到/ehcache.xml资源或出现问题，则将使用默认配置。</p><figure class="highlight xml"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">&lt;?xml version="1.0" encoding="UTF-8"?&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">ehcache</span> <span class="attr">xmlns:xsi</span>=<span class="string">"http://www.w3.org/2001/XMLSchema-instance"</span></span></span><br><span class="line"><span class="tag">        <span class="attr">xsi:noNamespaceSchemaLocation</span>=<span class="string">"http://ehcache.org/ehcache.xsd"</span></span></span><br><span class="line"><span class="tag">        <span class="attr">updateCheck</span>=<span class="string">"false"</span>&gt;</span></span><br><span class="line">   <span class="comment">&lt;!--</span></span><br><span class="line"><span class="comment">      diskStore：为缓存路径，ehcache分为内存和磁盘两级，此属性定义磁盘的缓存位置。参数解释如下：</span></span><br><span class="line"><span class="comment">      user.home – 用户主目录</span></span><br><span class="line"><span class="comment">      user.dir – 用户当前工作目录</span></span><br><span class="line"><span class="comment">      java.io.tmpdir – 默认临时文件路径</span></span><br><span class="line"><span class="comment">    --&gt;</span></span><br><span class="line">   <span class="tag">&lt;<span class="name">diskStore</span> <span class="attr">path</span>=<span class="string">"./tmpdir/Tmp_EhCache"</span>/&gt;</span></span><br><span class="line">   </span><br><span class="line">   &lt;defaultCache</span><br><span class="line">           eternal="false"</span><br><span class="line">           maxElementsInMemory="10000"</span><br><span class="line">           overflowToDisk="false"</span><br><span class="line">           diskPersistent="false"</span><br><span class="line">           timeToIdleSeconds="1800"</span><br><span class="line">           timeToLiveSeconds="259200"</span><br><span class="line">           memoryStoreEvictionPolicy="LRU"/&gt;</span><br><span class="line"></span><br><span class="line">   &lt;cache</span><br><span class="line">           name="cloud_user"</span><br><span class="line">           eternal="false"</span><br><span class="line">           maxElementsInMemory="5000"</span><br><span class="line">           overflowToDisk="false"</span><br><span class="line">           diskPersistent="false"</span><br><span class="line">           timeToIdleSeconds="1800"</span><br><span class="line">           timeToLiveSeconds="1800"</span><br><span class="line">           memoryStoreEvictionPolicy="LRU"/&gt;</span><br><span class="line">   <span class="comment">&lt;!--</span></span><br><span class="line"><span class="comment">      defaultCache：默认缓存策略，当ehcache找不到定义的缓存时，则使用这个缓存策略。只能定义一个。</span></span><br><span class="line"><span class="comment">    --&gt;</span></span><br><span class="line">   <span class="comment">&lt;!--</span></span><br><span class="line"><span class="comment">     name:缓存名称。</span></span><br><span class="line"><span class="comment">     maxElementsInMemory:缓存最大数目</span></span><br><span class="line"><span class="comment">     maxElementsOnDisk：硬盘最大缓存个数。</span></span><br><span class="line"><span class="comment">     eternal:对象是否永久有效，一但设置了，timeout将不起作用。</span></span><br><span class="line"><span class="comment">     overflowToDisk:是否保存到磁盘，当缓存存储的数据达到maxInMemory限制时</span></span><br><span class="line"><span class="comment">     timeToIdleSeconds:设置对象在失效前的允许闲置时间（单位：秒）。仅当eternal=false对象不是永久有效时使用，可选属性，默认值是0，也就是可闲置时间无穷大。</span></span><br><span class="line"><span class="comment">     timeToLiveSeconds:设置对象在失效前允许存活时间（单位：秒）。最大时间介于创建时间和失效时间之间。仅当eternal=false对象不是永久有效时使用，默认是0.，也就是对象存活时间无穷大。</span></span><br><span class="line"><span class="comment">     diskPersistent：是否缓存虚拟机重启期数据 Whether the disk store persists between restarts of the Virtual Machine. The default value is false.</span></span><br><span class="line"><span class="comment">     diskSpoolBufferSizeMB：这个参数设置DiskStore（磁盘缓存）的缓存区大小。默认是30MB。每个Cache都应该有自己的一个缓冲区。</span></span><br><span class="line"><span class="comment">     diskExpiryThreadIntervalSeconds：磁盘失效线程运行时间间隔，默认是120秒。</span></span><br><span class="line"><span class="comment">     memoryStoreEvictionPolicy：当达到maxElementsInMemory限制时，Ehcache将会根据指定的策略去清理内存。默认策略是LRU（最近最少使用）。你可以设置为FIFO（先进先出）或是LFU（较少使用）。</span></span><br><span class="line"><span class="comment">     clearOnFlush：内存数量最大时是否清除。</span></span><br><span class="line"><span class="comment">     memoryStoreEvictionPolicy:可选策略有：LRU（最近最少使用，默认策略）、FIFO（先进先出）、LFU（最少访问次数）。</span></span><br><span class="line"><span class="comment">     FIFO，first in first out，这个是大家最熟的，先进先出。</span></span><br><span class="line"><span class="comment">     LFU， Less Frequently Used，就是上面例子中使用的策略，直白一点就是讲一直以来最少被使用的。如上面所讲，缓存的元素有一个hit属性，hit值最小的将会被清出缓存。</span></span><br><span class="line"><span class="comment">     LRU，Least Recently Used，最近最少使用的，缓存的元素有一个时间戳，当缓存容量满了，而又需要腾出地方来缓存新的元素的时候，那么现有缓存元素中时间戳离当前时间最远的元素将被清出缓存。</span></span><br><span class="line"><span class="comment">  --&gt;</span></span><br><span class="line"></span><br><span class="line"><span class="tag">&lt;/<span class="name">ehcache</span>&gt;</span></span><br></pre></td></tr></tbody></table></figure>]]></content>
      
      
      
    </entry>
    
    
    
    <entry>
      <title>算法技巧</title>
      <link href="/javanblog/2021/04/25/%E7%AE%97%E6%B3%95%E6%8A%80%E5%B7%A71/"/>
      <url>/javanblog/2021/04/25/%E7%AE%97%E6%B3%95%E6%8A%80%E5%B7%A71/</url>
      
        <content type="html"><![CDATA[<h1 id="双指针法"><a href="#双指针法" class="headerlink" title="双指针法"></a>双指针法</h1><blockquote><p> 这是一种使用两个指针互相配合来存储节点以便于运算的技巧</p></blockquote><p>适用于数组、链表等线性结构，常用思路有碰撞指针、滑动窗口、快慢指针。</p><h2 id="对撞指针"><a href="#对撞指针" class="headerlink" title="对撞指针"></a>对撞指针</h2><blockquote><p>leetcode第一题两数之和</p></blockquote><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">int</span>[] twoSum(<span class="keyword">int</span>[] nums, <span class="keyword">int</span> target) {</span><br><span class="line">        <span class="comment">//双指针法</span></span><br><span class="line">        <span class="comment">//采用对撞指针法，时间复杂度降低到 o（n）</span></span><br><span class="line">        <span class="keyword">int</span> len = nums.length;</span><br><span class="line">        <span class="keyword">int</span> left=<span class="number">0</span>,right=len-<span class="number">1</span>;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">int</span>[] res=<span class="keyword">new</span> <span class="keyword">int</span>[<span class="number">2</span>];</span><br><span class="line">        <span class="keyword">int</span>[] tmp1=<span class="keyword">new</span> <span class="keyword">int</span>[nums.length];</span><br><span class="line">        System.arraycopy(nums,<span class="number">0</span>,tmp1,<span class="number">0</span>,nums.length);</span><br><span class="line"></span><br><span class="line">        <span class="comment">//将数组排序</span></span><br><span class="line">        Arrays.sort(nums);</span><br><span class="line">        <span class="comment">//如何将排序后的数组下标和原有数组下标对应起来？？？？</span></span><br><span class="line"></span><br><span class="line">    </span><br><span class="line">        <span class="keyword">int</span> m=<span class="number">0</span>,n=<span class="number">0</span>;</span><br><span class="line">        <span class="keyword">for</span>(<span class="keyword">int</span> i = left,j=right;i&lt; j;){</span><br><span class="line">            <span class="keyword">if</span>(nums[i]+nums[j]==target){</span><br><span class="line">                m = i;</span><br><span class="line">                n = j;</span><br><span class="line">                <span class="keyword">break</span>;</span><br><span class="line">            }<span class="keyword">else</span> <span class="keyword">if</span>(nums[i]+nums[j]&gt;target){</span><br><span class="line">                <span class="comment">//右指针左移动</span></span><br><span class="line">                j--;</span><br><span class="line">            }<span class="keyword">else</span> <span class="keyword">if</span>(nums[i]+nums[j]&lt;target){</span><br><span class="line">                <span class="comment">//左指针右移动</span></span><br><span class="line">                i++;</span><br><span class="line">            }</span><br><span class="line">        }</span><br><span class="line">        <span class="comment">//两个数不能一样，只能用两个变量了</span></span><br><span class="line">        <span class="keyword">int</span> i,j;</span><br><span class="line">        <span class="keyword">for</span> ( i=<span class="number">0</span>;i&lt;nums.length;i++) {</span><br><span class="line">            <span class="keyword">if</span>(tmp1[i]==nums[m]){</span><br><span class="line">                res[<span class="number">0</span>] = i;</span><br><span class="line">                <span class="keyword">break</span>;</span><br><span class="line">            }</span><br><span class="line">        }</span><br><span class="line">        <span class="keyword">for</span> ( j=<span class="number">0</span>;i&lt;nums.length;j++) {</span><br><span class="line">            <span class="comment">// i!=j</span></span><br><span class="line">            <span class="keyword">if</span>(tmp1[j]==nums[n]&amp;&amp;i!=j){</span><br><span class="line">                res[<span class="number">1</span>] = j;</span><br><span class="line">                <span class="keyword">break</span>;</span><br><span class="line">            }</span><br><span class="line">        }</span><br><span class="line">        <span class="keyword">return</span> res;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">}</span><br><span class="line">**这道题时间复杂度巨高！！！为什么呢？？？用到了系统的排序算法，这也暗示我们在使用双指针法的时候，数组一般要有序！**</span><br><span class="line"></span><br><span class="line">主要学会这个思想！！！</span><br></pre></td></tr></tbody></table></figure><blockquote><p>leetcode881题救生艇</p></blockquote><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">numRescueBoats</span><span class="params">(<span class="keyword">int</span>[] people, <span class="keyword">int</span> limit)</span> </span>{</span><br><span class="line">            <span class="comment">//采用双指针法 对撞指针法</span></span><br><span class="line">            </span><br><span class="line">            <span class="comment">//对数组进行排序</span></span><br><span class="line">            Arrays.sort(people);</span><br><span class="line">            <span class="comment">//数组长度</span></span><br><span class="line">            <span class="keyword">int</span> len = people.length;</span><br><span class="line">            <span class="comment">//计数器及总和</span></span><br><span class="line">            <span class="keyword">int</span> count=<span class="number">0</span>,sum=<span class="number">0</span>;</span><br><span class="line">            <span class="comment">//长度为1时</span></span><br><span class="line">            <span class="keyword">if</span>(len==<span class="number">1</span>){</span><br><span class="line">                <span class="keyword">return</span> <span class="number">1</span>;</span><br><span class="line">            }</span><br><span class="line">            <span class="comment">//定义指针</span></span><br><span class="line">            <span class="keyword">int</span> i=<span class="number">0</span>,j=len-<span class="number">1</span>;</span><br><span class="line">            <span class="keyword">while</span>(i&lt;=j){</span><br><span class="line">         <span class="comment">//题目已经说明了一首船最多在两个人！！！</span></span><br><span class="line">             <span class="keyword">if</span>(people[i]+people[j]&lt;=limit){</span><br><span class="line">                     i++;</span><br><span class="line">                }</span><br><span class="line">                j--;</span><br><span class="line">                count++;</span><br><span class="line">            }  </span><br><span class="line">            <span class="keyword">return</span> count;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><h2 id="快慢指针"><a href="#快慢指针" class="headerlink" title="快慢指针"></a>快慢指针</h2><blockquote><p>leetcode第141题 环形链表</p></blockquote><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * Definition for singly-linked list.</span></span><br><span class="line"><span class="comment"> * class ListNode {</span></span><br><span class="line"><span class="comment"> *     int val;</span></span><br><span class="line"><span class="comment"> *     ListNode next;</span></span><br><span class="line"><span class="comment"> *     ListNode(int x) {</span></span><br><span class="line"><span class="comment"> *         val = x;</span></span><br><span class="line"><span class="comment"> *         next = null;</span></span><br><span class="line"><span class="comment"> *     }</span></span><br><span class="line"><span class="comment"> * }</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">boolean</span> <span class="title">hasCycle</span><span class="params">(ListNode head)</span> </span>{</span><br><span class="line">        ListNode fast ;</span><br><span class="line">        ListNode slow = fast = head;</span><br><span class="line">        <span class="keyword">if</span>(head==<span class="keyword">null</span>){</span><br><span class="line">            <span class="keyword">return</span> <span class="keyword">false</span>;</span><br><span class="line">        }</span><br><span class="line">        <span class="comment">//while循环里面，快指针如果没有循环，那么链表就终止了</span></span><br><span class="line">        <span class="keyword">while</span>(fast!=<span class="keyword">null</span>&amp;&amp;fast.next!=<span class="keyword">null</span>){</span><br><span class="line">            slow = slow.next;</span><br><span class="line">            fast = fast.next.next;</span><br><span class="line">            <span class="keyword">if</span>(slow==fast){</span><br><span class="line">                <span class="keyword">return</span> <span class="keyword">true</span>;</span><br><span class="line">            }</span><br><span class="line">           </span><br><span class="line">        }</span><br><span class="line">        <span class="keyword">return</span> <span class="keyword">false</span>;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><h1 id="二分查找法"><a href="#二分查找法" class="headerlink" title="二分查找法"></a>二分查找法</h1><p>此算法要求，数据结构是顺序存储且关键字有序</p><blockquote><p>leetcode704题二分查找</p></blockquote><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">search</span><span class="params">(<span class="keyword">int</span>[] nums, <span class="keyword">int</span> target)</span> </span>{</span><br><span class="line">        <span class="comment">//暴力解</span></span><br><span class="line">        <span class="comment">// for(int i =0; i&lt; nums.length; i++) {</span></span><br><span class="line">        <span class="comment">//     if(nums[i]==target){</span></span><br><span class="line">        <span class="comment">//         return i;</span></span><br><span class="line">        <span class="comment">//     }</span></span><br><span class="line">            </span><br><span class="line"></span><br><span class="line">        <span class="comment">// }</span></span><br><span class="line">        <span class="comment">// return -1;</span></span><br><span class="line"></span><br><span class="line">        <span class="comment">// 二分查找法</span></span><br><span class="line">        <span class="keyword">int</span> left = <span class="number">0</span>, right = nums.length - <span class="number">1</span>;</span><br><span class="line">        <span class="keyword">int</span> mid = (left + right) / <span class="number">2</span>;</span><br><span class="line">        <span class="keyword">while</span>(left&lt;=right){</span><br><span class="line">            <span class="keyword">if</span>(nums[mid]==target){</span><br><span class="line">                <span class="keyword">return</span> mid;</span><br><span class="line">            }<span class="keyword">else</span> <span class="keyword">if</span>(nums[mid]&gt;target){</span><br><span class="line">                right = mid - <span class="number">1</span>;</span><br><span class="line">            }<span class="keyword">else</span>{</span><br><span class="line">                left = mid + <span class="number">1</span>;</span><br><span class="line">            }</span><br><span class="line">            mid = (left + right) / <span class="number">2</span>;</span><br><span class="line">        } </span><br><span class="line">        <span class="keyword">return</span> -<span class="number">1</span>;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><blockquote><p>leetcode 35 搜索插入位置</p></blockquote><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">searchInsert</span><span class="params">(<span class="keyword">int</span>[] nums, <span class="keyword">int</span> target)</span> </span>{</span><br><span class="line">        <span class="keyword">int</span> left = <span class="number">0</span>, right = nums.length - <span class="number">1</span>;</span><br><span class="line">        <span class="keyword">while</span>(left &lt;= right) {</span><br><span class="line">            <span class="keyword">int</span> mid = (left + right) / <span class="number">2</span>;</span><br><span class="line">            <span class="keyword">if</span>(nums[mid] == target) {</span><br><span class="line">                <span class="keyword">return</span> mid;</span><br><span class="line">            } <span class="keyword">else</span> <span class="keyword">if</span>(nums[mid] &lt; target) {</span><br><span class="line">                left = mid + <span class="number">1</span>;</span><br><span class="line">            } <span class="keyword">else</span> {</span><br><span class="line">                right = mid - <span class="number">1</span>;</span><br><span class="line">            }</span><br><span class="line">        }</span><br><span class="line">        <span class="keyword">return</span> right+<span class="number">1</span>;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><blockquote><p>leetcode162寻找峰值</p></blockquote><p>这一题，我首先想到的是暴力解，讨论各种情况，成功提交！</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">findPeakElement</span><span class="params">(<span class="keyword">int</span>[] nums)</span> </span>{</span><br><span class="line">        <span class="comment">// 暴力解法</span></span><br><span class="line">        <span class="comment">// 先讨论数组长度《3的情况</span></span><br><span class="line">        <span class="keyword">int</span> len = nums.length;</span><br><span class="line">        <span class="keyword">if</span>(len == <span class="number">1</span>){</span><br><span class="line">            <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">        }<span class="keyword">else</span> <span class="keyword">if</span>(len == <span class="number">2</span>){</span><br><span class="line">            <span class="keyword">if</span>(nums[<span class="number">0</span>]&gt;nums[<span class="number">1</span>]){</span><br><span class="line">                <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">            }</span><br><span class="line">            <span class="keyword">else</span> <span class="keyword">if</span>(nums[<span class="number">0</span>]&lt;nums[<span class="number">1</span>]){</span><br><span class="line">                <span class="keyword">return</span> <span class="number">1</span>;</span><br><span class="line">            }</span><br><span class="line">        }</span><br><span class="line">        <span class="comment">//讨论数组长度》=3</span></span><br><span class="line">        <span class="comment">//定义三个指针</span></span><br><span class="line">        <span class="keyword">int</span> left = <span class="number">0</span>;</span><br><span class="line">        <span class="keyword">int</span> mid =  <span class="number">1</span>;</span><br><span class="line">        <span class="keyword">int</span> right = <span class="number">2</span>;</span><br><span class="line">        <span class="comment">// 讨论峰值在边界情况</span></span><br><span class="line">        <span class="keyword">if</span>(nums[<span class="number">0</span>]&gt;nums[<span class="number">1</span>]){</span><br><span class="line">            <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">        }</span><br><span class="line">        <span class="keyword">if</span>(nums[len-<span class="number">1</span>]&gt;nums[len-<span class="number">2</span>]){</span><br><span class="line">            <span class="keyword">return</span> len -<span class="number">1</span>;</span><br><span class="line">        }</span><br><span class="line">        <span class="comment">// 讨论峰值在区间内</span></span><br><span class="line">        <span class="keyword">while</span>(right &lt; len){</span><br><span class="line">            <span class="keyword">if</span>(nums[mid]&gt;nums[left]&amp;&amp;nums[mid]&gt;nums[right]){</span><br><span class="line">                <span class="keyword">return</span> mid;</span><br><span class="line">            }</span><br><span class="line">            left++;</span><br><span class="line">            mid++;</span><br><span class="line">            right++;</span><br><span class="line">        }</span><br><span class="line">    <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">findPeakElement</span><span class="params">(<span class="keyword">int</span>[] nums)</span> </span>{</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 二分法</span></span><br><span class="line">    <span class="comment">// 使用二分法关键是理解好核心逻辑，一般二分法要排序，但是这样排序后，索引就乱了</span></span><br><span class="line">    <span class="comment">// 重新审查题意，发现， nums[-1] = nums[n] = -∞</span></span><br><span class="line">    <span class="keyword">int</span> len = nums.length;</span><br><span class="line">    <span class="keyword">int</span> left = <span class="number">0</span>,right = len -<span class="number">1</span>;</span><br><span class="line">    <span class="keyword">int</span> mid = (left + right) / <span class="number">2</span>;</span><br><span class="line">    <span class="keyword">while</span>(left&lt;right){</span><br><span class="line">        <span class="comment">// 只要找到一个峰值就可以了！！！</span></span><br><span class="line">        <span class="comment">// 说明峰值在右侧</span></span><br><span class="line">        <span class="keyword">if</span>(nums[mid+<span class="number">1</span>]&gt;nums[mid]){</span><br><span class="line">            <span class="comment">//右边高，说明在mid右边有峰值，所以mid一定不是</span></span><br><span class="line">            <span class="comment">//mid已经不是了，排除掉</span></span><br><span class="line">            left = mid + <span class="number">1</span> ;</span><br><span class="line">        }</span><br><span class="line">        <span class="comment">// 说明峰值在左侧</span></span><br><span class="line">        <span class="keyword">else</span> {</span><br><span class="line">            <span class="comment">// 左边高，说明左边有峰值，可能mid就是</span></span><br><span class="line">         right = mid ;<span class="comment">// mid在下一次查找中还要考虑在内</span></span><br><span class="line">        }</span><br><span class="line">        <span class="comment">// 这里的代码很贼！，在找峰值的时候，右侧是left=mid+1,左侧是right=mid</span></span><br><span class="line">        <span class="comment">// 其实核心就是往右侧靠，因为最左侧，循环到底，相对于num[-1]也是右侧！！！</span></span><br><span class="line">        mid = (left + right) / <span class="number">2</span>;</span><br><span class="line">    }</span><br><span class="line">    <span class="keyword">return</span> left;   </span><br><span class="line">}</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure>]]></content>
      
      
      
    </entry>
    
    
    
    <entry>
      <title>Leetcode刷题笔记</title>
      <link href="/javanblog/2021/04/24/Leetcode%20%E5%88%B7%E9%A2%98%E8%AE%B0%E5%BD%95/"/>
      <url>/javanblog/2021/04/24/Leetcode%20%E5%88%B7%E9%A2%98%E8%AE%B0%E5%BD%95/</url>
      
        <content type="html"><![CDATA[<h1 id="Leetcode-刷题记录"><a href="#Leetcode-刷题记录" class="headerlink" title="Leetcode 刷题记录"></a>Leetcode 刷题记录</h1><h2 id="1-两数之和（2021-4-3）"><a href="#1-两数之和（2021-4-3）" class="headerlink" title="1.两数之和（2021.4.3）"></a>1.两数之和（2021.4.3）</h2><p>给定一个整数数组 nums 和一个整数目标值 target，请你在该数组中找出 和为目标值 的那 两个 整数，并返回它们的数组下标。</p><p>你可以假设每种输入只会对应一个答案。但是，数组中同一个元素在答案里不能重复出现。</p><p>你可以按任意顺序返回答案。</p><p>示例 1：</p><p>输入：nums = [2,7,11,15], target = 9<br>输出：[0,1]<br>解释：因为 nums[0] + nums[1] == 9 ，返回 [0, 1] 。<br>示例 2：</p><p>输入：nums = [3,2,4], target = 6<br>输出：[1,2]<br>示例 3：</p><p>输入：nums = [3,3], target = 6<br>输出：[0,1]</p><p><strong>分析：</strong></p><p>该题只有一个答案，并且同一个元素不能重复出现。很容易想到用暴力解法，遍历整个数组，返回结果。</p><p><strong>暴力解法：</strong></p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line">class Solution {</span><br><span class="line">    public int[] twoSum(int[] nums, int target) {</span><br><span class="line">       </span><br><span class="line">       //遍历数组</span><br><span class="line">       for(int i = 0; i &lt; nums.length-1; i++){</span><br><span class="line">       for(int j = i + 1; j &lt; nums.length; j++){</span><br><span class="line">       if(nums[j]+nums[i]==target){</span><br><span class="line">       return new int[]{i,j};</span><br><span class="line">       }</span><br><span class="line">       }</span><br><span class="line">       }</span><br><span class="line">       return new int[0];</span><br><span class="line">    }</span><br><span class="line">}</span><br><span class="line">//执行用时: 0 ms</span><br><span class="line">//内存消耗: 38.3 MB</span><br><span class="line"></span><br></pre></td></tr></tbody></table></figure><p><strong>哈希表法：</strong>在做第二次的时候，hashmap的containsKey()方法不知道如何使用！！！！</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line">class Solution {</span><br><span class="line">    public int[] twoSum(int[] nums, int target) {</span><br><span class="line">     </span><br><span class="line">    int length = nums.length; </span><br><span class="line">    //创建哈希表,哈希表下标为0开始</span><br><span class="line">    HashMap&lt;Integer,Integer&gt; hashmap = new HashMap&lt;&gt;(length-1);</span><br><span class="line">    //遍历，寻找有无target-x值</span><br><span class="line">    for(int i = 0; i &lt; length;i++){</span><br><span class="line">    if(hashmap.containsKey(target-nums[i])){</span><br><span class="line">//在哈希表中找到了target-x的值</span><br><span class="line">return new int[]{hashmap.get(target-nums[i]),i};</span><br><span class="line">}</span><br><span class="line">//否则将键值队存入hanshmap中</span><br><span class="line">hashmap.put(nums[i],i);</span><br><span class="line">    }</span><br><span class="line">    return new int[0];</span><br><span class="line">    </span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><h2 id="2-两数相加（2021-4-5）"><a href="#2-两数相加（2021-4-5）" class="headerlink" title="2.两数相加（2021.4.5）"></a>2.两数相加（2021.4.5）</h2><p>给你两个 非空 的链表，表示两个非负的整数。它们每位数字都是按照 逆序 的方式存储的，并且每个节点只能存储 一位 数字。</p><p>请你将两个数相加，并以相同形式返回一个表示和的链表。</p><p>你可以假设除了数字 0 之外，这两个数都不会以 0 开头。</p><p>示例 1：</p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/image-20210405094908270.png" alt="image-20210405094908270"></p><p>输入：l1 = [2,4,3], l2 = [5,6,4]<br>输出：[7,0,8]<br>解释：342 + 465 = 807.<br>示例 2：</p><p>输入：l1 = [0], l2 = [0]<br>输出：[0]<br>示例 3：</p><p>输入：l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]<br>输出：[8,9,9,9,0,0,0,1]</p><p><strong>分析：</strong></p><p>该题考察的是链表的操作，预先指针，执行指针以及一些数学逻辑（进位数通过加法补位）。</p><p>将两个链表看成是相同长度的进行遍历，如果一个链表较短则在前面补 00，比如 987 + 23 = 987 + 023 = 1010<br>每一位计算的同时需要考虑上一位的进位问题，而当前位计算结束后同样需要更新进位值<br>如果两个链表全部遍历完毕后，进位值为 11，则在新链表最前方添加节点 11<br><strong>小技巧：对于链表问题，返回结果为头结点时，通常需要先初始化一个预先指针 pre，该指针的下一个节点指向真正的头结点head。使用预先指针的目的在于链表初始化时无可用节点值，而且链表构造过程需要指针移动，进而会导致头指针丢失，无法返回结果。</strong></p><p><strong>心得：</strong>（这是题解）</p><p>做题的时候，可以用草稿纸进行流程图演算，不会画图的程序员不是好程序猿！！！</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br></pre></td><td class="code"><pre><span class="line">/**</span><br><span class="line"> * Definition for singly-linked list.</span><br><span class="line"> * public class ListNode {</span><br><span class="line"> *     int val;</span><br><span class="line"> *     ListNode next;</span><br><span class="line"> *     ListNode() {}</span><br><span class="line"> *     ListNode(int val) { this.val = val; }</span><br><span class="line"> *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }</span><br><span class="line"> * }</span><br><span class="line"> */</span><br><span class="line">class Solution {</span><br><span class="line">    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {</span><br><span class="line">        //定义预先指针和执行指针</span><br><span class="line">        ListNode pre = new ListNode(0);</span><br><span class="line">        ListNode cur = pre;</span><br><span class="line">        //定义进位数</span><br><span class="line">        int carry = 0;</span><br><span class="line">        //进行遍历</span><br><span class="line">        while(l1!=null||l2!=null){</span><br><span class="line">            int n1 = l1==null ? 0:l1.val;</span><br><span class="line">            int n2 = l2==null ? 0:l2.val;</span><br><span class="line">            //定义链表每个位置的值</span><br><span class="line">            int sum = n1+n2+carry;//这个进位数carry一定不能忘记！！！</span><br><span class="line">            //判断是否有进位</span><br><span class="line">            carry = sum / 10;</span><br><span class="line">            //将值存进链表中</span><br><span class="line">            sum = sum % 10;</span><br><span class="line">            cur.next = new ListNode(sum);</span><br><span class="line">            //执行指针 移动一格</span><br><span class="line">            cur = cur.next;</span><br><span class="line">            //l1 l2 链表移动</span><br><span class="line">            if(l1!=null){</span><br><span class="line">                l1 = l1.next;</span><br><span class="line">            }</span><br><span class="line">            if(l2!=null){</span><br><span class="line">                l2 = l2.next;</span><br><span class="line">            }</span><br><span class="line">        }</span><br><span class="line">        //最后进位是一的话，就要补位</span><br><span class="line">        if(carry==1){</span><br><span class="line">            cur.next = new ListNode(1);</span><br><span class="line">        }</span><br><span class="line">        //为什么是返回 pre.next呢？？？ </span><br><span class="line">        //因为pre所指向的数据是无效的数据0，只是用来标记的，该指针的下一个节点指向真正的头结点head</span><br><span class="line">        return pre.next;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>这是第二次做题发现的问题。第一，链表节点要先建立起来，才能一路next。第二，考虑链表的空指针问题。第三，考虑进位加法的次序问题。第四，考虑结尾节点有无进位，是否需要创建链表。</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * Definition for singly-linked list.</span></span><br><span class="line"><span class="comment"> * public class ListNode {</span></span><br><span class="line"><span class="comment"> *     int val;</span></span><br><span class="line"><span class="comment"> *     ListNode next;</span></span><br><span class="line"><span class="comment"> *     ListNode() {}</span></span><br><span class="line"><span class="comment"> *     ListNode(int val) { this.val = val; }</span></span><br><span class="line"><span class="comment"> *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }</span></span><br><span class="line"><span class="comment"> * }</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line">    <span class="function"><span class="keyword">public</span> ListNode <span class="title">addTwoNumbers</span><span class="params">(ListNode l1, ListNode l2)</span> </span>{</span><br><span class="line">        <span class="comment">/*</span></span><br><span class="line"><span class="comment">        分析：</span></span><br><span class="line"><span class="comment">        若两数同位，各个数字相加，并加上进位，其中进位为 0 或者 1。</span></span><br><span class="line"><span class="comment">        若两数不同位，较短位补零，再加上进位。</span></span><br><span class="line"><span class="comment">        这是一个链表结构，对链表进行的操作，注意预先指针和执行指针的用法</span></span><br><span class="line"><span class="comment">        */</span></span><br><span class="line"></span><br><span class="line">        <span class="comment">//定义预先指针和执行指针</span></span><br><span class="line">        ListNode pre = <span class="keyword">new</span> ListNode(<span class="number">0</span>);</span><br><span class="line">        ListNode cur = pre;</span><br><span class="line"></span><br><span class="line">        <span class="comment">//默认进位是0</span></span><br><span class="line">        <span class="keyword">int</span> pos = <span class="number">0</span>;</span><br><span class="line"></span><br><span class="line">        <span class="comment">//进行遍历</span></span><br><span class="line">        <span class="keyword">while</span>(l1!=<span class="keyword">null</span> || l2!=<span class="keyword">null</span>){</span><br><span class="line">            <span class="comment">//数字相加,如果这样子的话，会遇到数字+空指针的情况，报出空指针异常。</span></span><br><span class="line">            <span class="comment">// int sum = l1.val+l2.val;</span></span><br><span class="line">            <span class="keyword">int</span> x = l1==<span class="keyword">null</span> ? <span class="number">0</span> : l1.val;</span><br><span class="line">            <span class="keyword">int</span> y = l2==<span class="keyword">null</span> ? <span class="number">0</span> : l2.val;</span><br><span class="line">            <span class="keyword">int</span> sum = x+y + pos; </span><br><span class="line"></span><br><span class="line"></span><br><span class="line">            <span class="comment">//确定进位</span></span><br><span class="line">            <span class="comment">// int pos = sum / 10;</span></span><br><span class="line">            <span class="comment">//确定结果数字!!! 记住这里要进位啊</span></span><br><span class="line">            <span class="keyword">int</span> result = sum % <span class="number">10</span> ;</span><br><span class="line"></span><br><span class="line">            <span class="comment">//这里再次确认进位，为下一个服务</span></span><br><span class="line">            pos = sum / <span class="number">10</span>;</span><br><span class="line">            <span class="comment">// cur.val = result;这里会报空指针异常！！！原因：你都没有定义节点啊</span></span><br><span class="line">            cur.next = <span class="keyword">new</span> ListNode(result);</span><br><span class="line">            <span class="comment">//指针下移</span></span><br><span class="line">            cur = cur.next;</span><br><span class="line"></span><br><span class="line">            <span class="comment">//判断l1 和 l2 指针情况</span></span><br><span class="line">            <span class="keyword">if</span>(l1!=<span class="keyword">null</span>){</span><br><span class="line">                l1 = l1.next;</span><br><span class="line">            }</span><br><span class="line">            <span class="keyword">if</span>(l2!=<span class="keyword">null</span>){</span><br><span class="line">                l2 = l2.next;</span><br><span class="line">            }</span><br><span class="line">        }</span><br><span class="line">        <span class="comment">//如果最后一个进位为 那么还要再创建一个结尾节点</span></span><br><span class="line">        <span class="keyword">if</span>(pos ==<span class="number">1</span>){</span><br><span class="line">            cur.next = <span class="keyword">new</span> ListNode(<span class="number">1</span>);</span><br><span class="line">        }</span><br><span class="line">        </span><br><span class="line">        <span class="comment">//返回链表节点</span></span><br><span class="line">        <span class="keyword">return</span> pre.next;</span><br><span class="line">         </span><br><span class="line">    }</span><br><span class="line">    <span class="comment">// return null;</span></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>这是别人的优化代码：</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line">class Solution {</span><br><span class="line">    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {</span><br><span class="line">        ListNode head = new ListNode(l1.val + l2.val);</span><br><span class="line">        ListNode cur = head;</span><br><span class="line">        while(l1.next != null || l2.next != null){</span><br><span class="line">            l1 = l1.next != null ? l1.next : new ListNode();</span><br><span class="line">            l2 = l2.next != null ? l2.next : new ListNode();</span><br><span class="line">            cur.next = new ListNode(l1.val + l2.val + cur.val / 10);</span><br><span class="line">            cur.val %= 10;</span><br><span class="line">            cur = cur.next;</span><br><span class="line">        }</span><br><span class="line">        if(cur.val &gt;= 10){</span><br><span class="line">            cur.next = new ListNode(cur.val / 10);</span><br><span class="line">            cur.val %= 10;</span><br><span class="line">        }</span><br><span class="line">        return head;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><h2 id="3-无重复字符的最长字串（2021-4-10）"><a href="#3-无重复字符的最长字串（2021-4-10）" class="headerlink" title="3.无重复字符的最长字串（2021.4.10）"></a>3.无重复字符的最长字串（2021.4.10）</h2><p>给定一个字符串，请你找出其中不含有重复字符的 <strong>最长子串</strong> 的长度。</p><p>示例 1:</p><p>输入: s = “abcabcbb”<br>输出: 3<br>解释: 因为无重复字符的最长子串是 “abc”，所以其长度为 3。<br>示例 2:</p><p>输入: s = “bbbbb”<br>输出: 1<br>解释: 因为无重复字符的最长子串是 “b”，所以其长度为 1。<br>示例 3:</p><p>输入: s = “pwwkew”<br>输出: 3<br>解释: 因为无重复字符的最长子串是 “wke”，所以其长度为 3。<br>     请注意，你的答案必须是 子串 的长度，”pwke” 是一个子序列，不是子串。<br>示例 4:</p><p>输入: s = “”<br>输出: 0</p><p>提示：</p><p>0 &lt;= s.length &lt;= 5 * 104<br>s 由英文字母、数字、符号和空格组成<br>通过次数931,090提交次数2,525,077</p><p><strong>分析：本题考察的是滑动窗口。再进行最大子串的寻找过程中，通过滑动左指针，并且不断比较maxlen。</strong></p><p><strong>错误解法：</strong></p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br></pre></td><td class="code"><pre><span class="line">class Solution {</span><br><span class="line">    public int lengthOfLongestSubstring(String s) {</span><br><span class="line">        </span><br><span class="line">        // count[0] = 0;</span><br><span class="line">        int len = s.length();</span><br><span class="line">        //定义计数数组</span><br><span class="line">        int[] count = new int[len];</span><br><span class="line">        if(s == ""){</span><br><span class="line">            return count[0];</span><br><span class="line">        }else{</span><br><span class="line">            int temp = 0;</span><br><span class="line">            for(int j = 0; j &lt; 10;j++){</span><br><span class="line">                HashMap&lt;Character ,Integer&gt; hashmap = new HashMap&lt;&gt;();</span><br><span class="line">                for(int i = temp ; i &lt; len; i++){</span><br><span class="line">                    if(hashmap.containsKey(s.charAt(i))){</span><br><span class="line">                        break;</span><br><span class="line">                    }else{</span><br><span class="line">                        hashmap.put(s.charAt(i),i);</span><br><span class="line">                        count[j]++;</span><br><span class="line">                        temp++;</span><br><span class="line">                }</span><br><span class="line">            }</span><br><span class="line">        }</span><br><span class="line">    }</span><br><span class="line">    int max = 0;</span><br><span class="line">    for(int x =0; x&lt;len;x++){   </span><br><span class="line">        if(max&lt;count[x]){</span><br><span class="line">            max = count[x];</span><br><span class="line">        }     </span><br><span class="line">    }</span><br><span class="line">   return max;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><strong>若测试案例是 dvdf，则输出结果为2，实际结果是3。因为上面的解法中，没有进行窗口的滑动（将左指针滑到已经出现字符的下一个上），而是进行指针的跳跃，将指针跳跃到重复字符的位置，这种思路是不对的，不满足题目的要求。</strong></p><h4 id="解法2：-滑动窗口法"><a href="#解法2：-滑动窗口法" class="headerlink" title="解法2： 滑动窗口法"></a>解法2： 滑动窗口法</h4><p><strong>正确思路：</strong></p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">lengthOfLongestSubstring</span><span class="params">(String s)</span> </span>{</span><br><span class="line">        <span class="comment">//定义最大的字串长度</span></span><br><span class="line">        <span class="keyword">int</span> maxlen = <span class="number">0</span>;</span><br><span class="line">        <span class="comment">//初始的左值针为 0</span></span><br><span class="line">        <span class="keyword">int</span> left= <span class="number">0</span>;</span><br><span class="line">        <span class="keyword">int</span> len = s.length();</span><br><span class="line">        HashMap&lt;Character, Integer&gt; hashMap = <span class="keyword">new</span> HashMap&lt;&gt;();</span><br><span class="line">        <span class="comment">//进行遍历</span></span><br><span class="line">        <span class="keyword">for</span> (<span class="keyword">int</span> right = <span class="number">0</span>; right &lt;len ; right++) {</span><br><span class="line">            <span class="keyword">if</span>(hashMap.containsKey(s.charAt(right))){</span><br><span class="line">                <span class="comment">//如果哈希表中包含该字符，更新左值针</span></span><br><span class="line">                <span class="comment">//为何要使用Math.max函数，取left和hashMap.get(s.charAt(right))+1，其中</span></span><br><span class="line"><span class="comment">//                hashMap.get(s.charAt(right))+1代表在之前出现的字符向后滑动一格。</span></span><br><span class="line">                <span class="comment">//情况一：在用例为abba中，right=2时，left更新为2，当right=3（为字符a时）,left更新为1，明显错误</span></span><br><span class="line">                left = Math.max(left,hashMap.get(s.charAt(right))+<span class="number">1</span>);</span><br><span class="line">            }</span><br><span class="line">            <span class="comment">//否则存入哈希表中</span></span><br><span class="line">            hashMap.put(s.charAt(right),right);</span><br><span class="line">            <span class="comment">//更新最大字串长度</span></span><br><span class="line">            maxlen = Math.max(maxlen,right-left+<span class="number">1</span>);</span><br><span class="line">        }</span><br><span class="line">        <span class="keyword">return</span>  maxlen;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>注意：这才是滑动窗口！！！</p><h2 id="数组模块"><a href="#数组模块" class="headerlink" title="数组模块"></a>数组模块</h2><h3 id="题号35：-搜索插入位置2021-4-24"><a href="#题号35：-搜索插入位置2021-4-24" class="headerlink" title="题号35： 搜索插入位置2021/4/24"></a>题号35： 搜索插入位置2021/4/24</h3><p>给定一个排序数组和一个目标值，在数组中找到目标值，并返回其索引。如果目标值不存在于数组中，返回它将会被按顺序插入的位置。</p><p>你可以假设数组中无重复元素。</p><p>示例 1:</p><p>输入: [1,3,5,6], 5<br>输出: 2<br>示例 2:</p><p>输入: [1,3,5,6], 2<br>输出: 1<br>示例 3:</p><p>输入: [1,3,5,6], 7<br>输出: 4<br>示例 4:</p><p>输入: [1,3,5,6], 0<br>输出: 0</p><p>解法1:暴力解法（时间复杂度 o（n））</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">searchInsert</span><span class="params">(<span class="keyword">int</span>[] nums, <span class="keyword">int</span> target)</span> </span>{</span><br><span class="line">        <span class="comment">//获取数组长度</span></span><br><span class="line">        <span class="keyword">int</span> len = nums.length;</span><br><span class="line">        <span class="comment">//遍历，判断是否有元素存在</span></span><br><span class="line">        <span class="keyword">for</span>(<span class="keyword">int</span> i =<span class="number">0</span>;i&lt;len;i++){</span><br><span class="line">            <span class="keyword">if</span>(target==nums[i]){</span><br><span class="line">                <span class="comment">//若有直接返回下标</span></span><br><span class="line">                <span class="keyword">return</span> i;</span><br><span class="line">            }</span><br><span class="line">        }</span><br><span class="line">        <span class="comment">//若元素不存在，判断首位位置</span></span><br><span class="line">        <span class="keyword">if</span>(target&lt;nums[<span class="number">0</span>]){</span><br><span class="line">            <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">        }<span class="keyword">else</span> <span class="keyword">if</span>(target&gt;nums[len-<span class="number">1</span>]){</span><br><span class="line">            <span class="keyword">return</span> len;</span><br><span class="line">        }</span><br><span class="line">        <span class="keyword">else</span>{</span><br><span class="line">            <span class="comment">//接着判断中间位置</span></span><br><span class="line">            <span class="keyword">for</span>(<span class="keyword">int</span> j=<span class="number">0</span>;j&lt;len-<span class="number">1</span>;j++){</span><br><span class="line">                <span class="keyword">if</span>(target&gt;nums[j]&amp;&amp;target&lt;nums[j+<span class="number">1</span>]){</span><br><span class="line">                    <span class="keyword">return</span> j+<span class="number">1</span>;</span><br><span class="line">                }</span><br><span class="line">            }</span><br><span class="line">        }</span><br><span class="line">     <span class="keyword">return</span> <span class="number">0</span>;   </span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><h4 id="解法2：二分查找"><a href="#解法2：二分查找" class="headerlink" title="解法2：二分查找"></a><strong>解法2：二分查找</strong></h4><p><strong>（时间复杂度 o（logn））</strong></p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">searchInsert</span><span class="params">(<span class="keyword">int</span>[] nums, <span class="keyword">int</span> target)</span> </span>{</span><br><span class="line">        <span class="comment">//左指针和右指针</span></span><br><span class="line">        <span class="keyword">int</span> left = <span class="number">0</span>, right = nums.length - <span class="number">1</span>;</span><br><span class="line">        <span class="comment">//边界条件是 左《= 右</span></span><br><span class="line">        <span class="keyword">while</span>(left &lt;= right) {</span><br><span class="line">            <span class="comment">//二分值</span></span><br><span class="line">            <span class="keyword">int</span> mid = (left + right) / <span class="number">2</span>;</span><br><span class="line">            <span class="keyword">if</span>(nums[mid] == target) {</span><br><span class="line">                <span class="comment">//元素相同，返回下标</span></span><br><span class="line">                <span class="keyword">return</span> mid;</span><br><span class="line">            } <span class="keyword">else</span> <span class="keyword">if</span>(nums[mid] &lt; target) {</span><br><span class="line">                <span class="comment">//说明target在右侧</span></span><br><span class="line">                left = mid + <span class="number">1</span>;</span><br><span class="line">            } <span class="keyword">else</span> {</span><br><span class="line">                <span class="comment">//说明target在左侧</span></span><br><span class="line">                right = mid - <span class="number">1</span>;</span><br><span class="line">            }</span><br><span class="line">        }</span><br><span class="line">        <span class="comment">//这里选用left是因为 left破坏了循坏条件</span></span><br><span class="line">        <span class="comment">//也可以return right + 1;(right+1==left)</span></span><br><span class="line">        <span class="keyword">return</span> left;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><em><u><strong>思考：什么时候用二分法？二分法有其他变种嘛？</strong></u></em></p><p>ans：</p><p>二分法的使用必须在数组有序的情况下使用，只有数组有序，那么target值才知道是在左边还是在右边，实现的业务逻辑就是依靠left和right指针。时间复杂度：O(logn)，空间复杂度：O(1)</p><p>二分法有三个变种，主要是看target值得区间范围。</p><p><strong>变种一：target在【left，right】</strong></p><p><strong>「思考为什么要写while(left &lt;= right)， 为什么要写right = middle - 1」</strong>。</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">int</span> n = nums.size();</span><br><span class="line"><span class="keyword">int</span> left = <span class="number">0</span>;</span><br><span class="line"><span class="keyword">int</span> right = n - <span class="number">1</span>; <span class="comment">// 定义target在左闭右闭的区间里，[left, right]    </span></span><br><span class="line"><span class="keyword">while</span> (left &lt;= right) { <span class="comment">// 当left==right，区间[left, right]依然有效</span></span><br><span class="line">        </span><br><span class="line">            <span class="keyword">int</span> middle = left + ((right - left) / <span class="number">2</span>);<span class="comment">// 防止溢出 等同于(left + right)/2</span></span><br><span class="line">            <span class="keyword">if</span> (nums[middle] &gt; target) {</span><br><span class="line">                right = middle - <span class="number">1</span>; <span class="comment">// target 在左区间，所以[left, middle - 1]</span></span><br><span class="line">            } <span class="keyword">else</span> <span class="keyword">if</span> (nums[middle] &lt; target) {</span><br><span class="line">                left = middle + <span class="number">1</span>; <span class="comment">// target 在右区间，所以[middle + 1, right]</span></span><br><span class="line">            } <span class="keyword">else</span> { <span class="comment">// nums[middle] == target</span></span><br><span class="line">                <span class="keyword">return</span> middle;</span><br><span class="line">            }</span><br><span class="line">        }</span><br></pre></td></tr></tbody></table></figure><p><strong>变种二：target在【left，right）</strong></p><p><strong>「思考为什么要写while (left &lt; right)， 为什么要写right = middle」</strong>。</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">int</span> n = nums.size();</span><br><span class="line"><span class="keyword">int</span> left = <span class="number">0</span>;</span><br><span class="line"><span class="keyword">int</span> right = n; <span class="comment">// 定义target在左闭右开的区间里，[left, right)  target</span></span><br><span class="line"><span class="keyword">while</span> (left &lt; right) { <span class="comment">// 因为left == right的时候，在[left, right)是无效的空间</span></span><br><span class="line">            <span class="keyword">int</span> middle = left + ((right - left) &gt;&gt; <span class="number">1</span>);</span><br><span class="line">            <span class="keyword">if</span> (nums[middle] &gt; target) {</span><br><span class="line">                right = middle; <span class="comment">// target 在左区间，在[left, middle)中</span></span><br><span class="line">            } <span class="keyword">else</span> <span class="keyword">if</span> (nums[middle] &lt; target) {</span><br><span class="line">                left = middle + <span class="number">1</span>; <span class="comment">// target 在右区间，在 [middle+1, right)中</span></span><br><span class="line">            } <span class="keyword">else</span> { <span class="comment">// nums[middle] == target</span></span><br><span class="line">                <span class="keyword">return</span> middle; <span class="comment">// 数组中找到目标值的情况，直接返回下标</span></span><br><span class="line">            }</span><br><span class="line">        }</span><br></pre></td></tr></tbody></table></figure><p><a href="https://leetcode-cn.com/problems/binary-search/solution/er-fen-cha-zhao-de-xun-huan-bu-bian-liang-zhi-yao-/">参考解答</a></p><h3 id="题号27：-移除元素2021-4-24"><a href="#题号27：-移除元素2021-4-24" class="headerlink" title="题号27： 移除元素2021/4/24"></a>题号27： 移除元素2021/4/24</h3><p>给你一个数组 nums 和一个值 val，你需要 原地 移除所有数值等于 val 的元素，并返回移除后数组的新长度。</p><p>不要使用额外的数组空间，你必须仅使用 O(1) 额外空间并 原地 修改输入数组。</p><p>元素的顺序可以改变。你不需要考虑数组中超出新长度后面的元素。</p><p>说明:</p><p>为什么返回数值是整数，但输出的答案是数组呢?</p><p>请注意，输入数组是以「引用」方式传递的，这意味着在函数里修改输入数组对于调用者是可见的。</p><p>你可以想象内部操作如下:</p><p>// nums 是以“引用”方式传递的。也就是说，不对实参作任何拷贝<br>int len = removeElement(nums, val);</p><p>// 在函数里修改输入数组对于调用者是可见的。<br>// 根据你的函数返回的长度, 它会打印出数组中 该长度范围内 的所有元素。<br>for (int i = 0; i &lt; len; i++) {<br>    print(nums[i]);<br>}</p><p>示例 1：</p><p>输入：nums = [3,2,2,3], val = 3<br>输出：2, nums = [2,2]<br>解释：函数应该返回新的长度 2, 并且 nums 中的前两个元素均为 2。你不需要考虑数组中超出新长度后面的元素。例如，函数返回的新长度为 2 ，而 nums = [2,2,3,3] 或 nums = [2,2,0,0]，也会被视作正确答案。<br>示例 2：</p><p>输入：nums = [0,1,2,2,3,0,4,2], val = 2<br>输出：5, nums = [0,1,4,0,3]<br>解释：函数应该返回新的长度 5, 并且 nums 中的前五个元素为 0, 1, 3, 0, 4。注意这五个元素可为任意顺序。你不需要考虑数组中超出新长度后面的元素。</p><p><strong>解法1：暴力解法</strong></p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">removeElement</span><span class="params">(<span class="keyword">int</span>[] nums, <span class="keyword">int</span> val)</span> </span>{</span><br><span class="line">        <span class="comment">//定义长度</span></span><br><span class="line">        <span class="keyword">int</span> len = nums.length;</span><br><span class="line">        <span class="comment">//计数器：定义删除得个数</span></span><br><span class="line">        <span class="keyword">int</span> count = <span class="number">0</span>;</span><br><span class="line">        <span class="comment">//遍历</span></span><br><span class="line">        <span class="keyword">for</span>(<span class="keyword">int</span> i=<span class="number">0</span>;i&lt;len;i++){</span><br><span class="line">            <span class="comment">//如果等于val，那么进行数组移除操作</span></span><br><span class="line">            <span class="keyword">if</span>(nums[i]==val){</span><br><span class="line">                <span class="comment">//移除操作</span></span><br><span class="line">                <span class="keyword">for</span>(<span class="keyword">int</span> j = i ; j&lt;len-<span class="number">1</span>;j++){</span><br><span class="line">                    nums[j]=nums[j+<span class="number">1</span>];</span><br><span class="line">                }</span><br><span class="line">                <span class="comment">//后面补位-1，因为测试val都是正数</span></span><br><span class="line">                nums[len-<span class="number">1</span>]=-<span class="number">1</span>;</span><br><span class="line">                <span class="comment">//计数器加一</span></span><br><span class="line">                count++;</span><br><span class="line">                <span class="comment">//找到一个后，那么i要减少一，因为后面不上来啦！</span></span><br><span class="line">                i--;</span><br><span class="line">            }</span><br><span class="line">            </span><br><span class="line">        }</span><br><span class="line">        <span class="comment">//最终数组得长度</span></span><br><span class="line">        <span class="keyword">return</span> len - count;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>代码优化：</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line">先设定变量 idx，指向待插入位置。idx 初始值为 <span class="number">0</span></span><br><span class="line">然后从题目的「要求/保留逻辑」出发，来决定当遍历到任意元素 x 时，应该做何种决策：</span><br><span class="line">如果当前元素 x 与移除元素 val 相同，那么跳过该元素。</span><br><span class="line">如果当前元素 x 与移除元素 val 不同，那么我们将其放到下标 idx 的位置，并让 idx 自增右移。</span><br><span class="line">最终得到的 idx 即是答案</span><br><span class="line"></span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">removeElement</span><span class="params">(<span class="keyword">int</span>[] nums, <span class="keyword">int</span> val)</span> </span>{</span><br><span class="line">        <span class="keyword">int</span> idx = <span class="number">0</span>;</span><br><span class="line">        <span class="keyword">for</span> (<span class="keyword">int</span> x : nums) {</span><br><span class="line">            <span class="keyword">if</span> (x != val) </span><br><span class="line">                <span class="comment">//这一步相当于重置nums数组了</span></span><br><span class="line">                nums[idx++] = x;</span><br><span class="line">        }</span><br><span class="line">        <span class="keyword">return</span> idx;</span><br><span class="line">    }</span><br><span class="line">}</span><br><span class="line"></span><br></pre></td></tr></tbody></table></figure><h4 id="解法2：-双指针法"><a href="#解法2：-双指针法" class="headerlink" title="解法2： 双指针法"></a>解法2： 双指针法</h4><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">removeElement</span><span class="params">(<span class="keyword">int</span>[] nums, <span class="keyword">int</span> val)</span> </span>{</span><br><span class="line">        <span class="keyword">int</span> j = nums.length - <span class="number">1</span>;</span><br><span class="line">        <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i &lt;= j; i++) {</span><br><span class="line">            <span class="keyword">if</span> (nums[i] == val) {</span><br><span class="line">                <span class="comment">//遇到相同元素进行交换</span></span><br><span class="line">                swap(nums, i--, j--);</span><br><span class="line">            }</span><br><span class="line">        }</span><br><span class="line">        <span class="keyword">return</span> j + <span class="number">1</span>;</span><br><span class="line">    }</span><br><span class="line">    <span class="function"><span class="keyword">void</span> <span class="title">swap</span><span class="params">(<span class="keyword">int</span>[] nums, <span class="keyword">int</span> i, <span class="keyword">int</span> j)</span> </span>{</span><br><span class="line">        <span class="keyword">int</span> tmp = nums[i];</span><br><span class="line">        nums[i] = nums[j];</span><br><span class="line">        nums[j] = tmp;</span><br><span class="line">    }</span><br><span class="line">}</span><br><span class="line"></span><br></pre></td></tr></tbody></table></figure><h3 id="题号209：-长度最小的子数组2021-4-24"><a href="#题号209：-长度最小的子数组2021-4-24" class="headerlink" title="题号209： 长度最小的子数组2021/4/24"></a>题号209： 长度最小的子数组2021/4/24</h3><p>给定一个含有 n 个正整数的数组和一个正整数 target 。</p><p>找出该数组中满足其和 ≥ target 的长度最小的 连续子数组 [numsl, numsl+1, …, numsr-1, numsr] ，并返回其长度。如果不存在符合条件的子数组，返回 0 。</p><p>示例 1：</p><p>输入：target = 7, nums = [2,3,1,2,4,3]<br>输出：2<br>解释：子数组 [4,3] 是该条件下的长度最小的子数组。<br>示例 2：</p><p>输入：target = 4, nums = [1,4,4]<br>输出：1<br>示例 3：</p><p>输入：target = 11, nums = [1,1,1,1,1,1,1,1]<br>输出：0</p><p><strong>解法1 :暴力解法</strong></p><p>首先最容易想到的是暴力求解，使用两个 for 循环，一个 for 循环固定一个数字比如 m，另一个 for 循环从 m 的下一个元素开始累加，当和大于等于 s 的时候终止内层循环，顺便记录下最小长度</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">minSubArrayLen</span><span class="params">(<span class="keyword">int</span> s, <span class="keyword">int</span>[] nums)</span> </span>{</span><br><span class="line">        <span class="comment">//先定义min值是一个无穷大</span></span><br><span class="line">        <span class="keyword">int</span> min = Integer.MAX_VALUE;</span><br><span class="line">        <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i &lt; nums.length; i++) {</span><br><span class="line">            <span class="comment">//第一层循环，每次循环都重复定义sum</span></span><br><span class="line">            <span class="keyword">int</span> sum = nums[i];</span><br><span class="line">            <span class="comment">//发现 单次值&gt;s,直接return 1；</span></span><br><span class="line">            <span class="keyword">if</span> (sum &gt;= s)</span><br><span class="line">                <span class="keyword">return</span> <span class="number">1</span>;</span><br><span class="line">            <span class="comment">//进入二层循环</span></span><br><span class="line">            <span class="keyword">for</span> (<span class="keyword">int</span> j = i + <span class="number">1</span>; j &lt; nums.length; j++) {</span><br><span class="line">                <span class="comment">//sum进行累加</span></span><br><span class="line">                sum += nums[j];</span><br><span class="line">                <span class="comment">//发现sum值》s，记录最小得累加个数，注意，这里累加个数为 j-i+1</span></span><br><span class="line">                <span class="comment">//如何每次都记录号最小得值？？？别在用数组进行储存和判断了！！！</span></span><br><span class="line">                <span class="comment">//直接使用Math.min(a,b)或者Math.max(a,b)</span></span><br><span class="line">                <span class="keyword">if</span> (sum &gt;= s) {</span><br><span class="line">                    min = Math.min(min, j - i + <span class="number">1</span>);</span><br><span class="line">                    <span class="comment">//找到min值，就可以跳出二层循环了</span></span><br><span class="line">                    <span class="keyword">break</span>;</span><br><span class="line">                }</span><br><span class="line">            }</span><br><span class="line">        }</span><br><span class="line">        <span class="comment">//判断min值是不是原始得，若是，说明总的sum值一直都没有超过s，自然个数就是return 0；</span></span><br><span class="line">        <span class="keyword">return</span> min == Integer.MAX_VALUE ? <span class="number">0</span> : min;</span><br><span class="line">    }</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>心得：这个暴力解法，挺看考察逻辑的！！！有两个技巧要学习下</p><p>一、每次循环重复定义</p><p>二、寻找最小值，用Math函数得min和max方法</p><h4 id="解法2：滑动窗口法"><a href="#解法2：滑动窗口法" class="headerlink" title="解法2：滑动窗口法"></a>解法2：滑动窗口法</h4><p>我们把数组中的元素不停的入队，直到总和大于等于 s 为止，接着记录下队列中元素的个数，然后再不停的出队，直到队列中元素的和小于 s 为止（如果不小于 s，也要记录下队列中元素的个数，这个个数其实就是不小于 s 的连续子数组长度，我们要记录最小的即可）。接着再把数组中的元素添加到队列中……重复上面的操作，直到数组中的元素全部使用完为止。<br>这里以 [2,3,1,2,4,3] 举例画个图来看下</p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/10ca012c2f0170afcac5e5996add20c32c36a82f4bb4a6187897bb948ace5fe2-image.png" alt="image.png"></p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/2da8cf86a2a3df3c95ed7d95add574dca2d8bae8420addd0fa6b8c55fa3db081-image.png" alt="image.png"></p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/ca74b1a2ad0eb5a4ebf8647a332161b140c8ebdd71cd5d19bef16e9bf0a43c95-image.png" alt="image.png"></p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/72f39b5cd7eb5f866e24d0a31eb3eac7d57cf3ad202ad40d30f103833c1f5a69-image.png" alt="image.png"></p><p>上面画的是使用队列，但在代码中我们不直接使用队列，我们使用两个指针，一个指向队头一个指向队尾，我们来看下代码</p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">minSubArrayLen</span><span class="params">(<span class="keyword">int</span> s, <span class="keyword">int</span>[] nums)</span> </span>{</span><br><span class="line">        <span class="comment">//lo为队列头 li为队列尾</span></span><br><span class="line">        <span class="keyword">int</span> lo = <span class="number">0</span>, hi = <span class="number">0</span>, sum = <span class="number">0</span>, min = Integer.MAX_VALUE;</span><br><span class="line">        <span class="keyword">while</span> (hi &lt; nums.length) {</span><br><span class="line">            sum += nums[hi++];</span><br><span class="line">            <span class="keyword">while</span> (sum &gt;= s) {</span><br><span class="line">                min = Math.min(min, hi - lo);</span><br><span class="line">                sum -= nums[lo++];</span><br><span class="line">            }</span><br><span class="line">        }</span><br><span class="line">        <span class="keyword">return</span> min == Integer.MAX_VALUE ? <span class="number">0</span> : min;</span><br><span class="line">    }</span><br><span class="line"><span class="comment">//用双指针来实现滑动窗口和队列进出得数据结构</span></span><br><span class="line"></span><br></pre></td></tr></tbody></table></figure><p>心得：我觉得这道题核心在于，理解滑动窗口得意义，一个窗口（连续得数组，不停得滑动），滑动过程中如何记录我们想要得数据？（用math的min和max函数！！！）</p><h3 id="题号59：螺旋矩阵-II"><a href="#题号59：螺旋矩阵-II" class="headerlink" title="题号59：螺旋矩阵 II"></a>题号59：螺旋矩阵 II</h3><h4 id="解法1-模拟法"><a href="#解法1-模拟法" class="headerlink" title="解法1 模拟法"></a>解法1 模拟法</h4><p>思路：<br>生成一个 n×n 空矩阵 mat，随后模拟整个向内环绕的填入过程：<br>定义当前左右上下边界 l,r,t,b，初始值 num = 1，迭代终止值 tar = n * n；<br>当 num &lt;= tar 时，始终按照 从左到右 从上到下 从右到左 从下到上 填入顺序循环，每次填入后：<br>执行 num += 1：得到下一个需要填入的数字；<br>更新边界：例如从左到右填完后，上边界 t += 1，相当于上边界向内缩 1。<br>使用num &lt;= tar而不是l &lt; r || t &lt; b作为迭代条件，是为了解决当n为奇数时，矩阵中心数字无法在迭代过程中被填充的问题。<br>最终返回 mat 即可。</p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/ccff416fa39887c938d36fec8e490e1861813d3bba7836eda941426f13420759-Picture1.png" alt="Picture1.png"></p><figure class="highlight java"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">int</span>[][] generateMatrix(<span class="keyword">int</span> n) {</span><br><span class="line">        <span class="comment">//模拟法的应用：如何解决边界条件</span></span><br><span class="line">        <span class="comment">//四个边界</span></span><br><span class="line">        <span class="keyword">int</span> l=<span class="number">0</span>,r=n-<span class="number">1</span>,t=<span class="number">0</span>,b=n-<span class="number">1</span>;</span><br><span class="line">        <span class="comment">//count存放数值</span></span><br><span class="line">        <span class="keyword">int</span> count = <span class="number">1</span>,val = n*n;</span><br><span class="line">        <span class="comment">//这是结果数组</span></span><br><span class="line">        <span class="keyword">int</span> [][] res = <span class="keyword">new</span> <span class="keyword">int</span> [n][n];</span><br><span class="line">        <span class="keyword">while</span>(count&lt;=val){</span><br><span class="line">            <span class="comment">//从左往右</span></span><br><span class="line">            <span class="keyword">for</span> (<span class="keyword">int</span> i = l; i &lt;= r ; i++) {</span><br><span class="line">                res[t][i] = count++;</span><br><span class="line">            }</span><br><span class="line">            <span class="comment">//top边界要下移</span></span><br><span class="line">            t++;</span><br><span class="line"></span><br><span class="line">            <span class="comment">//从上往下</span></span><br><span class="line">            <span class="keyword">for</span> (<span class="keyword">int</span> i = t; i &lt;= b ; i++) {</span><br><span class="line">                res[i][r] = count++;</span><br><span class="line">            }</span><br><span class="line">            <span class="comment">//right边界要左移</span></span><br><span class="line">            r--;</span><br><span class="line"></span><br><span class="line">            <span class="comment">//从右往左</span></span><br><span class="line">            <span class="keyword">for</span> (<span class="keyword">int</span> i = r; i &gt;= l ; i--) {</span><br><span class="line">                res[b][i] = count++;</span><br><span class="line">            }</span><br><span class="line">            <span class="comment">//bottom边界要上移</span></span><br><span class="line">            b--;</span><br><span class="line">            <span class="comment">//从下往上</span></span><br><span class="line">            <span class="keyword">for</span> (<span class="keyword">int</span> i = b; i &gt;= t ; i--) {</span><br><span class="line">                res[i][l] = count++;</span><br><span class="line">            }</span><br><span class="line">            <span class="comment">//left边界要右移</span></span><br><span class="line">            l++;</span><br><span class="line">        }</span><br><span class="line">        <span class="keyword">return</span> res;</span><br><span class="line">    }</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><h1 id="注意前方高能！！！接下来的算法学习思路为："><a href="#注意前方高能！！！接下来的算法学习思路为：" class="headerlink" title="注意前方高能！！！接下来的算法学习思路为："></a>注意前方高能！！！接下来的算法学习思路为：</h1><p>1.b栈小姐姐手把手教你刷leetcode视频（主要是学会常用算法套路）</p><p>2.leetcode按照模块tag刷题，同时配合代码随想录中的由易到难的路线</p><p>3.图解算法看一下，了解算法有哪些，重点怎么学习！！！</p>]]></content>
      
      
      
    </entry>
    
    
    
    <entry>
      <title>Git初级学习笔记</title>
      <link href="/javanblog/2021/04/23/Git%E5%AD%A6%E4%B9%A0%E7%AC%94%E8%AE%B0/"/>
      <url>/javanblog/2021/04/23/Git%E5%AD%A6%E4%B9%A0%E7%AC%94%E8%AE%B0/</url>
      
        <content type="html"><![CDATA[<h1 id="基础知识"><a href="#基础知识" class="headerlink" title="基础知识"></a>基础知识</h1><h2 id="什么是版本控制"><a href="#什么是版本控制" class="headerlink" title="什么是版本控制"></a>什么是版本控制</h2><p>版本控制（Revision control）是一种在开发的过程中用于管理我们对文件、目录或工程等内容的修改历史，方便查看更改历史记录，备份以便恢复以前的版本的软件工程技术。</p><ul><li>实现跨区域多人协同开发</li><li>追踪和记载一个或者多个文件的历史记录</li><li>组织和保护你的源代码和文档</li><li>统计工作量</li><li>并行开发、提高开发效率</li><li>跟踪记录整个软件的开发过程</li><li>减轻开发人员的负担，节省时间，同时降低人为错误</li></ul><p><strong>简单说就是用于管理多人协同开发项目的技术</strong>。</p><p>没有进行版本控制或者版本控制本身缺乏正确的流程管理，在软件开发过程中将会引入很多问题，如软件代码的一致性、软件内容的冗余、软件过程的事物性、软件开发过程中的并发性、软件源代码的安全性，以及软件的整合等问题。</p><p>无论是工作还是学习，或者是自己做笔记，都经历过这样一个阶段！我们就迫切需要一个版本控制工具！</p><p><strong>多人开发就必须要使用版本控制</strong>！</p><h2 id="常见的版本控制工具"><a href="#常见的版本控制工具" class="headerlink" title="常见的版本控制工具"></a>常见的版本控制工具</h2><p>我们学习的东西，一定是当下最流行的！</p><p>主流的版本控制器有如下这些：</p><ul><li><strong>Git</strong></li><li><strong>SVN</strong>（Subversion）</li><li><strong>CVS</strong>（Concurrent Versions System）</li><li><strong>VSS</strong>（Micorosoft Visual SourceSafe）</li><li><strong>TFS</strong>（Team Foundation Server）</li><li>Visual Studio Online</li></ul><p>版本控制产品非常的多（Perforce、Rational ClearCase、RCS（GNU Revision Control System）、Serena Dimention、SVK、BitKeeper、Monotone、Bazaar、Mercurial、SourceGear Vault），现在影响力最大且使用最广泛的是Git与SVN</p><h2 id="版本控制分类"><a href="#版本控制分类" class="headerlink" title="版本控制分类"></a>版本控制分类</h2><p><strong>1、本地版本控制</strong></p><p>记录文件每次的更新，可以对每个版本做一个快照，或是记录补丁文件，适合个人用，如RCS。</p><p><strong>2、集中版本控制  SVN</strong></p><p>所有的版本数据都保存在服务器上，协同开发者从服务器上同步更新或上传自己的修改</p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/image-20210423185757483.png" alt="image-20210423185757483"></p><p>所有的版本数据都存在服务器上，用户的本地只有自己以前所同步的版本，如果不连网的话，用户就看不到历史版本，也无法切换版本验证问题，或在不同分支工作。而且，所有数据都保存在单一的服务器上，有很大的风险这个服务器会损坏，这样就会丢失所有的数据，当然可以定期备份。代表产品：SVN、CVS、VSS</p><p><strong>3、分布式版本控制     Git</strong></p><p><strong>每个人都拥有全部的代码！安全隐患！</strong></p><p>所有版本信息仓库全部同步到本地的每个用户，这样就可以在本地查看所有版本历史，可以离线在本地提交，只需在连网时push到相应的服务器或其他用户那里。由于每个用户那里保存的都是所有的版本数据，只要有一个用户的设备没有问题就可以恢复所有的数据，但这增加了本地存储空间的占用。</p><p>不会因为服务器损坏或者网络问题，造成不能工作的情况！</p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/image-20210423185932075.png" alt="image-20210423185932075"></p><h2 id="Git与SVN的主要区别"><a href="#Git与SVN的主要区别" class="headerlink" title="Git与SVN的主要区别"></a>Git与SVN的主要区别</h2><p>SVN是集中式版本控制系统，版本库是集中放在中央服务器的，而工作的时候，用的都是自己的电脑，所以首先要从中央服务器得到最新的版本，然后工作，完成工作后，需要把自己做完的活推送到中央服务器。集中式版本控制系统是必须联网才能工作，对网络带宽要求较高。</p><p><strong><u>Git是分布式版本控制系统，没有中央服务器，每个人的电脑就是一个完整的版本库，工作的时候不需要联网了，因为版本都在自己电脑上。</u></strong></p><p>协同的方法是这样的：比如说自己在电脑上改了文件A，其他人也在电脑上改了文件A，这时，你们两之间只需把各自的修改推送给对方，就可以互相看到对方的修改了。</p><p><u><strong>Git可以直接看到更新了哪些代码和文件！</strong></u></p><p><strong>Git是目前世界上最先进的分布式版本控制系统。</strong></p><h2 id="Git环境配置"><a href="#Git环境配置" class="headerlink" title="Git环境配置"></a>Git环境配置</h2><p><strong>软件下载</strong></p><p>打开 [git官网] <a href="https://git-scm.com/%EF%BC%8C%E4%B8%8B%E8%BD%BDgit%E5%AF%B9%E5%BA%94%E6%93%8D%E4%BD%9C%E7%B3%BB%E7%BB%9F%E7%9A%84%E7%89%88%E6%9C%AC%E3%80%82">https://git-scm.com/，下载git对应操作系统的版本。</a></p><p>所有东西下载慢的话就可以去找镜像！</p><p>官网下载太慢，我们可以使用淘宝镜像下载：<a href="http://npm.taobao.org/mirrors/git-for-windows/">http://npm.taobao.org/mirrors/git-for-windows/</a></p><p>下载对应的版本即可安装！</p><p>安装：无脑下一步即可！安装完毕就可以使用了！</p><p><strong>启动Git</strong></p><p>安装成功后在开始菜单中会有Git项，菜单下有3个程序：任意文件夹下右键也可以看到对应的程序！</p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/image-20210423190002507.png" alt="image-20210423190002507"></p><p><strong>Git Bash：</strong>Unix与Linux风格的命令行，使用最多，推荐最多</p><p><strong>Git CMD：</strong>Windows风格的命令行</p><p><strong>Git GUI</strong>：图形界面的Git，不建议初学者使用，尽量先熟悉常用命令</p><p> <strong>常用的Linux命令</strong></p><p>平时一定要多使用这些基础的命令！</p><p>1）、cd : 改变目录。</p><p>2）、cd . . 回退到上一个目录，直接cd进入默认目录</p><p>3）、pwd : 显示当前所在的目录路径。</p><p>4）、ls(ll):  都是列出当前目录中的所有文件，只不过ll(两个ll)列出的内容更为详细。</p><p>5）、touch : 新建一个文件 如 touch index.js 就会在当前目录下新建一个index.js文件。</p><p>6）、rm:  删除一个文件, rm index.js 就会把index.js文件删除。</p><p>7）、mkdir:  新建一个目录,就是新建一个文件夹。</p><p>8）、rm -r :  删除一个文件夹, rm -r src 删除src目录</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">rm -rf / 切勿在Linux中尝试！删除电脑中全部文件！</span><br></pre></td></tr></tbody></table></figure><p>9）、mv 移动文件, mv index.html src index.html 是我们要移动的文件, src 是目标文件夹,当然, 这样写,必须保证文件和目标文件夹在同一目录下。</p><p>10）、reset 重新初始化终端/清屏。</p><p>11）、clear 清屏。</p><p>12）、history 查看命令历史。</p><p>13）、help 帮助。</p><p>14）、exit 退出。</p><p>15）、#表示注释</p><h2 id="Git配置"><a href="#Git配置" class="headerlink" title="Git配置"></a>Git配置</h2><p>所有的配置文件，其实都保存在本地！</p><p>查看配置 git config -l</p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/image-20210423190020971.png" alt="image-20210423190020971"></p><p>查看不同级别的配置文件：</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">#查看系统</span><br><span class="line">configgit config --system --list　　</span><br><span class="line">#查看当前用户（global）配置</span><br><span class="line">git config --global  --list</span><br></pre></td></tr></tbody></table></figure><p><strong>Git相关的配置文件：</strong></p><p>1）、Git\etc\gitconfig  ：Git 安装目录下的 gitconfig   –system 系统级</p><p>2）、C:\Users\Administrator\ .gitconfig   只适用于当前登录用户的配置  –global 全局</p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/image-20210423190037846.png" alt="image-20210423190037846"></p><p>这里可以直接编辑配置文件，通过命令设置后会响应到这里。</p><p> <strong>设置用户名与邮箱（用户标识，必要）</strong></p><p>当你安装Git后首先要做的事情是设置你的用户名称和e-mail地址。这是非常重要的，因为每次Git提交都会使用该信息。它被永远的嵌入到了你的提交中：</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">git config --global user.name "kuangshen"  </span><br><span class="line">#名称</span><br><span class="line">git config --global user.email 24736743@qq.com   </span><br><span class="line">#邮箱</span><br></pre></td></tr></tbody></table></figure><p>只需要做一次这个设置，如果你传递了–global 选项，因为Git将总是会使用该信息来处理你在系统中所做的一切操作。如果你希望在一个特定的项目中使用不同的名称或e-mail地址，你可以在该项目中运行该命令而不要–global选项。总之–global为全局配置，不加为某个项目的特定配置。</p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/image-20210423190051360.png" alt="image-20210423190051360"></p><h2 id="Git基本理论（重要）"><a href="#Git基本理论（重要）" class="headerlink" title="Git基本理论（重要）"></a><strong>Git基本理论（重要）</strong></h2><h2 id="三个区域"><a href="#三个区域" class="headerlink" title="三个区域"></a>三个区域</h2><p>Git本地有三个工作区域：工作目录（Working Directory）、暂存区(Stage/Index)、资源库(Repository或Git Directory)。如果在加上远程的git仓库(Remote Directory)就可以分为四个工作区域。文件在这四个区域之间的转换关系如下：</p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/image-20210423190108878.png" alt="image-20210423190108878"></p><ul><li>Workspace：工作区，就是你平时存放项目代码的地方</li><li>Index / Stage：暂存区，用于临时存放你的改动，事实上它只是一个文件，保存即将提交到文件列表信息</li><li>Repository：仓库区（或本地仓库），就是安全存放数据的位置，这里面有你提交到所有版本的数据。其中HEAD指向最新放入仓库的版本</li><li>Remote：远程仓库，托管代码的服务器，可以简单的认为是你项目组中的一台电脑用于远程数据交换</li></ul><p><strong>本地的三个区域确切的说应该是git仓库中HEAD指向的版本：</strong></p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/image-20210423190126730.png" alt="image-20210423190126730"></p><ul><li>Directory：使用Git管理的一个目录，也就是一个仓库，包含我们的工作空间和Git的管理空间。</li><li>WorkSpace：需要通过Git进行版本控制的目录和文件，这些目录和文件组成了工作空间。</li><li>.git：存放Git管理信息的目录，初始化仓库的时候自动创建。</li><li>Index/Stage：暂存区，或者叫待提交更新区，在提交进入repo之前，我们可以把所有的更新放在暂存区。</li><li>Local Repo：本地仓库，一个存放在本地的版本库；HEAD会只是当前的开发分支（branch）。</li><li>Stash：隐藏，是一个工作状态保存栈，用于保存/恢复WorkSpace中的临时状态。</li></ul><h2 id="工作流程"><a href="#工作流程" class="headerlink" title="工作流程"></a>工作流程</h2><p>git的工作流程一般是这样的：</p><p>１、在工作目录中添加、修改文件；</p><p>２、将需要进行版本管理的文件放入暂存区域；</p><p>３、将暂存区域的文件提交到git仓库。</p><p>因此，git管理的文件有三种状态：已修改（modified）,已暂存（staged）,已提交(committed)</p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/image-20210423190149356.png" alt="image-20210423190149356"></p><h2 id="Git项目搭建（重要）"><a href="#Git项目搭建（重要）" class="headerlink" title="Git项目搭建（重要）"></a>Git项目搭建（重要）</h2><p><strong>创建工作目录与常用指令</strong></p><p>工作目录（WorkSpace)一般就是你希望Git帮助你管理的文件夹，可以是你项目的目录，也可以是一个空目录，建议不要有中文。</p><p>日常使用只要记住下图6个命令：<img src="data:image/gif;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVQImWNgYGBgAAAABQABh6FO1AAAAABJRU5ErkJggg==" alt="图片"></p><p><strong>本地仓库搭建</strong></p><p>创建本地仓库的方法有两种：一种是创建全新的仓库，另一种是克隆远程仓库。</p><p>1、创建全新的仓库，需要用GIT管理的项目的根目录执行：</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"># 在当前目录新建一个Git代码库</span><br><span class="line">$ git init</span><br></pre></td></tr></tbody></table></figure><p>2、执行后可以看到，仅仅在项目目录多出了一个.git目录，关于版本等的所有信息都在这个目录里面。</p><p><strong>克隆远程仓库</strong></p><p>1、另一种方式是克隆远程目录，由于是将远程服务器上的仓库完全镜像一份至本地！</p><figure class="highlight"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"># 克隆一个项目和它的整个代码历史(版本信息)</span><br><span class="line">$ git clone [url]  # https://gitee.com/kuangstudy/openclass.git</span><br></pre></td></tr></tbody></table></figure><p>2、去 gitee 或者 github 上克隆一个测试！</p><h2 id="Git文件操作"><a href="#Git文件操作" class="headerlink" title="Git文件操作"></a>Git文件操作</h2><p><strong>文件的四种状态</strong></p><p>版本控制就是对文件的版本控制，要对文件进行修改、提交等操作，首先要知道文件当前在什么状态，不然可能会提交了现在还不想提交的文件，或者要提交的文件没提交上。</p><ul><li>Untracked: 未跟踪, 此文件在文件夹中, 但并没有加入到git库, 不参与版本控制. 通过git add 状态变为Staged.</li><li>Unmodify: 文件已经入库, 未修改, 即版本库中的文件快照内容与文件夹中完全一致. 这种类型的文件有两种去处, 如果它被修改, 而变为Modified. 如果使用git rm移出版本库, 则成为Untracked文件</li><li>Modified: 文件已修改, 仅仅是修改, 并没有进行其他的操作. 这个文件也有两个去处, 通过git add可进入暂存staged状态, 使用git checkout 则丢弃修改过, 返回到unmodify状态, 这个git checkout即从库中取出文件, 覆盖当前修改 !</li><li>Staged: 暂存状态. 执行git commit则将修改同步到库中, 这时库中的文件和本地文件又变为一致, 文件为Unmodify状态. 执行git reset HEAD filename取消暂存, 文件状态为Modified</li></ul><p> <strong>查看文件状态</strong></p><p>上面说文件有4种状态，通过如下命令可以查看到文件的状态：</p><figure class="highlight"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">#查看指定文件状态git status [filename]</span><br><span class="line">#查看所有文件状态git status</span><br><span class="line"># git add .                  添加所有文件到暂存区</span><br><span class="line"># git commit -m "消息内容"    提交暂存区中的内容到本地仓库 -m 提交信息</span><br></pre></td></tr></tbody></table></figure><p> <strong>忽略文件</strong></p><p>有些时候我们不想把某些文件纳入版本控制中，比如数据库文件，临时文件，设计文件等</p><p>在主目录下建立”.gitignore”文件，此文件有如下规则：</p><ol><li>忽略文件中的空行或以井号（#）开始的行将会被忽略。</li><li>可以使用Linux通配符。例如：星号（*）代表任意多个字符，问号（？）代表一个字符，方括号（[abc]）代表可选字符范围，大括号（{string1,string2,…}）代表可选的字符串等。</li><li>如果名称的最前面有一个感叹号（!），表示例外规则，将不被忽略。</li><li>如果名称的最前面是一个路径分隔符（/），表示要忽略的文件在此目录下，而子目录中的文件不忽略。</li><li>如果名称的最后面是一个路径分隔符（/），表示要忽略的是此目录下该名称的子目录，而非文件（默认文件或目录都忽略）。</li></ol><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">#为注释</span><br><span class="line">*.txt        #忽略所有 .txt结尾的文件,这样的话上传就不会被选中！</span><br><span class="line">!lib.txt     #但lib.txt除外</span><br><span class="line">/temp        #仅忽略项目根目录下的TODO文件,不包括其它目录</span><br><span class="line">tempbuild/       #忽略build/目录下的所有文件</span><br><span class="line">doc/*.txt    #会忽略 doc/notes.txt 但不包括 doc/server/arch.txt</span><br></pre></td></tr></tbody></table></figure><h2 id="使用码云"><a href="#使用码云" class="headerlink" title="使用码云"></a>使用码云</h2><p> <strong>github 是有墙的，比较慢，在国内的话，我们一般使用 gitee ，公司中有时候会搭建自己的gitlab服务器</strong></p><p>这个其实可以作为大家未来找工作的一个重要信息！</p><p>1、注册登录码云，完善个人信息</p><p>2、设置本机绑定SSH公钥，实现免密码登录！（免密码登录，这一步挺重要的，码云是远程仓库，我们是平时工作在本地仓库！)</p><h3 id="何谓公钥"><a href="#何谓公钥" class="headerlink" title="何谓公钥"></a>何谓公钥</h3><ul><li>1.很多服务器都是需要认证的，ssh认证是其中的一种。在客户端生成公钥，把生成的公钥添加到服务器，你以后连接服务器就不用每次都输入用户名和密码了。</li><li>2.很多git服务器都是用ssh认证方式，你需要把你生成的公钥发送给代码仓库管理员，让他给你添加到服务器上，你就可以通过ssh自由地拉取和提交代码了。</li></ul><h3 id="生成公钥"><a href="#生成公钥" class="headerlink" title="生成公钥"></a>生成公钥</h3><ul><li>1.如果通过上面的方式找不到公钥，你就需要先生成公钥了：ssh-keygen</li><li>2.接着会确认存放公钥的地址，默认就是上面说的路径，直接enter键确认</li><li>3.接着会要求输入密码和确认密码，如果不想设置密码直接不输入内容 按enter键</li></ul><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/20170802000320339.png" alt="图片"></p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/image-20210423190218610.png" alt="image-20210423190218610"></p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"># 进入 C:\Users\Administrator\.ssh 目录</span><br><span class="line"># 生成公钥</span><br><span class="line">ssh-keygen</span><br></pre></td></tr></tbody></table></figure><p>3、将公钥信息public key 添加到码云账户中即可！</p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/image-20210423190231684.png" alt="image-20210423190231684"></p><p>4、使用码云创建一个自己的仓库！</p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/image-20210423190250535.png" alt="image-20210423190250535"></p><p>许可证：开源是否可以随意转载，开源但是不能商业使用，不能转载，…  限制！</p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/image-20210423190317420.png" alt="image-20210423190317420"></p><p>克隆到本地！</p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/image-20210423190341956.png" alt="image-20210423190341956"></p><h2 id="IDEA中集成Git"><a href="#IDEA中集成Git" class="headerlink" title="IDEA中集成Git"></a>IDEA中集成Git</h2><p>1、新建项目，绑定git。</p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/image-20210423190359280.png" alt="image-20210423190359280"></p><p>注意观察idea中的变化</p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/image-20210423190417911.png" alt="image-20210423190417911"></p><p>2、修改文件，使用IDEA操作git。</p><ul><li>添加到暂存区</li><li>commit 提交</li><li>push到远程仓库</li></ul><p>3、提交测试</p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/image-20210423190430177.png" alt="image-20210423190430177"></p><h2 id="GIT分支"><a href="#GIT分支" class="headerlink" title="GIT分支"></a>GIT分支</h2><p>分支在GIT中相对较难，分支就是科幻电影里面的平行宇宙，如果两个平行宇宙互不干扰，那对现在的你也没啥影响。不过，在某个时间点，两个平行宇宙合并了，我们就需要处理一些问题了！<img src="data:image/gif;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVQImWNgYGBgAAAABQABh6FO1AAAAABJRU5ErkJggg==" alt="图片"></p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/image-20210423190447935.png" alt="image-20210423190447935"></p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/image-20210423190620188.png" alt="image-20210423190620188"></p><p>git分支中常用指令：</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"># 列出所有本地分支</span><br><span class="line">git branch</span><br><span class="line"># 列出所有远程分支</span><br><span class="line">git branch -r</span><br><span class="line"># 新建一个分支，但依然停留在当前分支</span><br><span class="line">git branch [branch-name]</span><br><span class="line"># 新建一个分支，并切换到该分支</span><br><span class="line">git checkout -b [branch]</span><br><span class="line"># 合并指定分支到当前分支</span><br><span class="line">$ git merge [branch]</span><br><span class="line"># 删除分支</span><br><span class="line">$ git branch -d [branch-name]</span><br><span class="line"># 删除远程分支</span><br><span class="line">$ git push origin --delete [branch-name]$ git branch -dr [remote/branch]</span><br></pre></td></tr></tbody></table></figure><p>IDEA中操作</p><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/image-20210423190640173.png" alt="image-20210423190640173"></p><p>如果同一个文件在合并分支时都被修改了则会引起冲突：</p><p><u><strong>解决的办法是我们可以修改冲突文件后重新提交！选择要保留他的代码还是你的代码！</strong></u></p><p><em><strong>master主分支应该非常稳定，用来发布新版本，一般情况下不允许在上面工作，工作一般情况下在新建的dev分支上工作，工作完后，比如上要发布，或者说dev分支代码稳定后可以合并到主分支master上来。</strong></em></p><h1 id="进阶知识"><a href="#进阶知识" class="headerlink" title="进阶知识"></a>进阶知识</h1><h2 id="指令的总结"><a href="#指令的总结" class="headerlink" title="指令的总结"></a>指令的总结</h2><h3 id="安装"><a href="#安装" class="headerlink" title="安装"></a>安装</h3><pre><code>git --version</code></pre><h3 id="初始化配置"><a href="#初始化配置" class="headerlink" title="初始化配置"></a>初始化配置</h3><pre><code>git config --global user.name "damu"git config --global user.email damu@example.com    git config --list</code></pre><h3 id="初始化仓库"><a href="#初始化仓库" class="headerlink" title="初始化仓库"></a>初始化仓库</h3><pre><code>git init</code></pre><h3 id="C-新增"><a href="#C-新增" class="headerlink" title="C(新增)"></a>C(新增)</h3><pre><code>在工作目录中新增文件git statusgit add ./git commit -m "msg"    </code></pre><h3 id="U-修改"><a href="#U-修改" class="headerlink" title="U(修改)"></a>U(修改)</h3><pre><code>在工作目录中修改文件git statusgit add ./git commit -m "msg"     </code></pre><h3 id="D-删除-amp-重命名"><a href="#D-删除-amp-重命名" class="headerlink" title="D(删除 &amp; 重命名)"></a>D(删除 &amp; 重命名)</h3><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">git rm 要删除的文件     git mv 老文件 新文件</span><br><span class="line">git  status             git  status</span><br><span class="line">git commit -m "msg"     git commit -m "msg"</span><br></pre></td></tr></tbody></table></figure><h3 id="R-查询"><a href="#R-查询" class="headerlink" title="R(查询)"></a>R(查询)</h3>   <figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">git  status   :  查看工作目录中文件的状态(已跟踪(已提交 已暂存 已修改) 未跟踪)</span><br><span class="line">  git  diff     :  查看未暂存的修改</span><br><span class="line">  git  diff --cache : 查看未提交的暂存</span><br><span class="line">  git  log --oneline : 查看提交记录</span><br></pre></td></tr></tbody></table></figure><h3 id="分支"><a href="#分支" class="headerlink" title="分支"></a>分支</h3><pre><code>分支的本质其实就是一个提交对象!!!HEAD:     是一个指针 它默认指向master分支 切换分支时其实就是让HEAD指向不同的分支    每次有新的提交时 HEAD都会带着当前指向的分支 一起往前移动git  log --oneline --decorate --graph --all : 查看整个项目的分支图  git branch : 查看分支列表git branch -v: 查看分支指向的最新的提交git branch name : 在当前提交对象上创建新的分支git branch name commithash: 在指定的提交对象上创建新的分支git checkout name :     切换分支git branch -d name : 删除空的分支 删除已经被合并的分支git branch -D name : 强制删除分支 </code></pre><p>   git分支本质</p><pre><code>分支本质是一个提交对象,所有的分支都会有机会被HEAD所引用(HEAD一个时刻只会指向一个分支)当我们有新的提交的时候 HEAD会携带当前持有的分支往前移动</code></pre><h3 id="git分支命令"><a href="#git分支命令" class="headerlink" title="git分支命令"></a>git分支命令</h3><pre><code>创建分支            : git branch branchname切换分支           : git checkout  branchname创建&amp;切换分支     : git checkout -b branchname版本穿梭(时光机) :  git branch branchname commitHash  普通删除分支      : git  branch -d branchname强制删除分支      : git  branch -D branchname合并分支         : git merge branchname    快进合并 --&gt; 不会产生冲突    典型合并 --&gt; 有机会产生冲突    解决冲突 --&gt; 打开冲突的文件 进行修改 add commit 查看分支列表 : git branch查看合并到当前分支的分支列表: git branch --merged    一旦出现在这个列表中 就应该删除查看没有合并到当前分支的分支列表: git branch&nbsp;--no-merged    一旦出现在这个列表中 就应该观察一下是否需要合并</code></pre><h3 id="git分支的注意点"><a href="#git分支的注意点" class="headerlink" title="git分支的注意点"></a>git分支的注意点</h3><pre><code>在切换的时候 一定要保证当前分支是干净的!!!    允许切换分支:         分支上所有的内容处于 已提交状态            (避免)分支上的内容是初始化创建 处于未跟踪状态        (避免)分支上的内容是初始化创建 第一次处于已暂存状态    不允许切分支:         分支上所有的内容处于 已修改状态  或 第二次以后的已暂存状态           在分支上的工作做到一半时 如果有切换分支的需求, 我们应该将现有的工作存储起来    git stash : 会将当前分支上的工作推到一个栈中    分支切换  进行其他工作 完成其他工作后 切回原分支    git stash apply : 将栈顶的工作内容还原 但不让任何内容出栈     git stash drop  : 取出栈顶的工作内容后 就应该将其删除(出栈)    git stash pop   :      git stash apply +  git stash drop     git stash list : 查看存储</code></pre><h3 id="后悔药"><a href="#后悔药" class="headerlink" title="后悔药"></a>后悔药</h3><pre><code>撤销工作目录的修改   :  git checkout -- filename撤销暂存区的修改     :  git reset HEAD  filename撤销提交             :  git commit --amend</code></pre><h3 id="reset三部曲"><a href="#reset三部曲" class="headerlink" title="reset三部曲"></a>reset三部曲</h3><pre><code>git reset --soft commithash    ---&gt; 用commithash的内容重置HEAD内容git reset [--mixed] commithash ---&gt; 用commithash的内容重置HEAD内容 重置暂存区git reset --hard commithash    ---&gt; 用commithash的内容重置HEAD内容 重置暂存区 重置工作目录</code></pre><h3 id="路径reset"><a href="#路径reset" class="headerlink" title="路径reset"></a>路径reset</h3><pre><code>所有的路径reset都要省略第一步!!!    第一步是重置HEAD内容  我们知道HEAD本质指向一个分支 分支的本质是一个提交对象     提交对象 指向一个树对象 树对象又很有可能指向多个git对象 一个git对象代表一个文件!!!    HEAD可以代表一系列文件的状态!!!!git reset [--mixed] commithash filename       用commithash中filename的内容重置暂存区</code></pre><h3 id="checkout深入理解"><a href="#checkout深入理解" class="headerlink" title="checkout深入理解"></a>checkout深入理解</h3><pre><code>git   checkout brancname  跟   git reset --hard commithash特别像    共同点        都需要重置 HEAD   暂存区   工作目录    区别         checkout对工作目录是安全的    reset --hard是强制覆盖         checkout动HEAD时不会带着分支走而是切换分支         reset --hard时是带着分支走         checkout + 路径      git checkout commithash  filename              重置暂存区           重置工作目录      git checkout -- filename            重置工作目录  </code></pre><p>​        三个必须懂得概念</p><pre><code>本地分支远程跟踪分支(remote/分支名)远程分支</code></pre><h3 id="远程协作的基本流程"><a href="#远程协作的基本流程" class="headerlink" title="远程协作的基本流程"></a>远程协作的基本流程</h3><pre><code>第一步: 项目经理创建一个空的远程仓库第二步: 项目经理创建一个待推送的本地仓库第三步: 为远程仓库配别名  配完用户名 邮箱第四步: 在本地仓库中初始化代码 提交代码第五步: 推送第六步: 邀请成员第七步: 成员克隆远程仓库第八步: 成员做出修改第九步: 成员推送自己的修改第十步: 项目经理拉取成员的修改</code></pre><h3 id="做跟踪"><a href="#做跟踪" class="headerlink" title="做跟踪"></a>做跟踪</h3><pre><code>克隆才仓库时 会自动为master做跟踪本地没有分支    git checkout --track 远程跟踪分支(remote/分支名)本地已经创建了分支    git branch -u 远程跟踪分支(remote/分支名)</code></pre><h3 id="推送"><a href="#推送" class="headerlink" title="推送"></a>推送</h3><pre><code>git push</code></pre><h3 id="拉取"><a href="#拉取" class="headerlink" title="拉取"></a>拉取</h3><pre><code>git pull</code></pre><h3 id="pull-request"><a href="#pull-request" class="headerlink" title="pull request"></a>pull request</h3><pre><code>让第三方人员参与到项目中 fork</code></pre><h3 id="使用频率最高的五个命令"><a href="#使用频率最高的五个命令" class="headerlink" title="使用频率最高的五个命令"></a>使用频率最高的五个命令</h3><pre><code>git statusgit addgit commitgit pushgit pull    </code></pre><p><img src="https://gitee.com/javan-lu/figure-bed/raw/master/img/11.jpg" alt="last"></p>]]></content>
      
      
      
    </entry>
    
    
    
    <entry>
      <title>JavaWeb笔记</title>
      <link href="/javanblog/2021/04/23/JavaWeb%E7%9F%A5%E8%AF%86%E7%82%B9%E6%80%BB%E7%BB%93/"/>
      <url>/javanblog/2021/04/23/JavaWeb%E7%9F%A5%E8%AF%86%E7%82%B9%E6%80%BB%E7%BB%93/</url>
      
        <content type="html"><![CDATA[<h1 id="JavaWeb知识点总结"><a href="#JavaWeb知识点总结" class="headerlink" title="JavaWeb知识点总结"></a>JavaWeb知识点总结</h1><p><strong>HTML、CSS、JS、JQuery、XML、Tomcat、Servlet程序、Filter过滤器、Listener监听器、jsp页面、EL表达式、JSTL标签库、Cookie技术、Session会话、JSON使用、Ajax请求</strong></p><h2 id="1、Html、Css、JS、JQuery"><a href="#1、Html、Css、JS、JQuery" class="headerlink" title="1、Html、Css、JS、JQuery"></a>1、Html、Css、JS、JQuery</h2><p><strong>网页的组成：内容（Html）、表现(Css)、行为（JS）。</strong></p><h3 id="1-1-HTML-Hyper-Text-Markup-Language-（超文本标记语言）"><a href="#1-1-HTML-Hyper-Text-Markup-Language-（超文本标记语言）" class="headerlink" title="1.1 HTML:Hyper Text Markup Language （超文本标记语言）"></a>1.1 <strong>HTML:Hyper Text Markup Language （超文本标记语言）</strong></h3><p>重点标签;</p><p><strong><!--form 标签就是表单input type=text 是文件输入框 value 设置默认显示内容input type=password 是密码输入框 value 设置默认显示内容input type=radio 是单选框 name 属性可以对其进行分组 checked="checked"表示默认选中input type=checkbox 是复选框 checked="checked"表示默认选中input type=reset 是重置按钮 value 属性修改按钮上的文本input type=submit 是提交按钮 value 属性修改按钮上的文本input type=button 是按钮 value 属性修改按钮上的文本input type=file 是文件上传域input type=hidden 是隐藏域 当我们要发送某些信息，而这些信息，不需要用户参与，就可以使用隐藏域（提交的时候同时发送给服务器）select 标签是下拉列表框option 标签是下拉列表框中的选项 selected="selected"设置默认选中textarea 表示多行文本输入框 （起始标签和结束标签中的内容是默认值）rows 属性设置可以显示几行的高度cols 属性设置每行可以显示几个字符宽度--></strong></p><form action="http://localhost:8080" method="post"><input type="hidden" name="action" value="login"><h1 align="center">用户注册</h1><table align="center"><tbody><tr><td> 用户名称：</td><td><input type="text" name="username" value="默认值"></td></tr><tr><td> 用户密码：</td><td><input type="password" name="password" value="abc"></td></tr><tr><td>性别：</td><td><input type="radio" name="sex" value="boy">男<input type="radio" name="sex" checked="checked" value="girl">女</td></tr><tr><td> 兴趣爱好：</td><td><input name="hobby" type="checkbox" checked="checked" value="java">Java<input name="hobby" type="checkbox" value="js">JavaScript<input name="hobby" type="checkbox" value="cpp">C++</td></tr><tr><td>国籍：</td><td><select name="country"><option value="none">--请选择国籍--</option><option value="cn" selected="selected">中国</option><option value="usa">美国</option><option value="jp">小日本</option></select></td></tr><tr><td>自我评价：</td><td><textarea name="desc" rows="10" cols="20">我才是默认值</textarea></td></tr><tr><td><input type="reset"></td><td align="center"><input type="submit"></td></tr></tbody></table></form><h3 id="1-2-Css-「层叠样式表单」"><a href="#1-2-Css-「层叠样式表单」" class="headerlink" title="1.2 Css:「层叠样式表单」"></a>1.2 Css:「层叠样式表单」</h3><p>把 css 样式写成一个单独的 css 文件，再通过 link 标签引入即可复用。</p><p>html 的 <link rel="stylesheet" type="text/css" href="./styles.css"> 标签 导入 css 样式文件。</p><p><strong>CSS三种选择器：</strong></p><p><strong>标签名选择器：</strong></p><p>div{<br>border: 1px solid yellow;<br>color: blue;<br>font-size: 30px;<br>}</p><p><strong>id 选择器：</strong></p><p>#id002{<br>color: red;<br>font-size: 20px;<br>border: 5px blue dotted ;<br>}</p><p><strong>class 选择器（类选择器）：</strong></p><p>.class01{<br>color: blue;<br>font-size: 30px;<br>border: 1px solid yellow;<br>}</p><h3 id="1-3-JavaScript语言"><a href="#1-3-JavaScript语言" class="headerlink" title="1.3 JavaScript语言"></a>1.3 JavaScript语言</h3><p><strong>JS 是弱类型，Java 是强类型</strong></p><ol><li>交互性（它可以做的就是信息的动态交互） </li><li> 安全性（不允许直接访问本地硬盘）</li><li> 跨平台性（只要是可以解释 JS 的浏览器都可以执行，和平台无关）</li></ol><p><strong>Js和Html代码的结合:或者标签中使用<script type="text/javascript"> </script>或者 使用 script 标签引入 单独的 JavaScript 代码文件。</strong></p><p><strong>JS 中的定义变量格式： var 变量名; var 变量名 = 值;</strong></p><p><strong>JavaScript 里特殊的值：</strong></p><p> undefined 未定义，所有 js 变量未赋于初始值的时候，默认值都是 undefined. </p><p> null 空值 </p><p> NaN 全称是：Not a Number。非数字。非数值。</p><p><strong>JavaScript函数：</strong></p><p>function 函数名(形参列表){ 函数体 }</p><p> 在 JavaScript 语言中，如何定义带有返回值的函数？ 只需要在函数体内直接使用 return 语句返回值即可！</p><p>或者</p><p>var 函数名 = function(形参列表) { 函数体 }</p><p><strong>js 中的事件：</strong>电脑输入设备与页面进行交互的响应。我们称之为事件</p><p><strong>常用的事件：</strong></p><p>onload 加载完成事件： 页面加载完成之后，常用于做页面 js 代码初始化操作 </p><p>onclick 单击事件： 常用于按钮的点击响应操作。 </p><p>onblur 失去焦点事件： 常用用于输入框失去焦点后验证其输入内容是否合法。 </p><p>onchange 内容发生改变事件： 常用于下拉列表和输入框内容发生改变后操作</p><p> onsubmit 表单提交事件：常用于表单提交前，验证所有表单项是否合法。</p><p><strong>事件的注册又分为静态注册和动态注册两种：</strong> </p><p>什么是事件的注册（绑定）？ 其实就是告诉浏览器，当事件响应后要执行哪些操作代码，叫事件注册或事件绑定。</p><p> <strong>静态注册事件：</strong></p><p>通过 html 标签的事件属性直接赋于事件响应后的代码，这种方式我们叫静态注册。 </p><p><strong>动态注册事件：</strong></p><p>是指先通过 js 代码得到标签的 dom 对象，然后再通过 dom 对象.事件名 = function(){} 这种形式赋于事件 响应后的代码，叫动态注册。 </p><p>DOM 全称是 Document Object Model 文档对象模型。</p><p><strong>DOM对象常用方法;</strong></p><p>document 对象的三个查询方法，如果有 id 属性，优先使用 getElementById 方法来进行查询<br>如果没有 id 属性，则优先使用 getElementsByName 方法来进行查询<br>如果 id 属性和 name 属性都没有最后再按标签名查 getElementsByTagName<br>以上三个方法，一定要在页面加载完成之后执行，才能查询到标签对象。</p><p><strong>动态注册基本步骤</strong>： 1、获取标签对象 2、标签对象.事件名 = fucntion(){}</p><p>window.onload = function () {<br>//1 获取标签对象<br>var passwordObj = document.getElementById(“password”);<br>// alert(passwordObj);<br>//2 通过标签对象.事件名 = function(){};<br>passwordObj.onblur = function () {<br>console.log(“动态注册失去焦点事件”);<br>}<br>}</p><h3 id="1-4-JQuery"><a href="#1-4-JQuery" class="headerlink" title="1.4 JQuery"></a>1.4 JQuery</h3><p><strong>也就是 JavaScript 和查询（Query），它就是辅助 JavaScript 开发的 js 类库。</strong></p><p>使用前要导入jquery类库</p><script type="text/javascript" src="../script/jquery-1.7.2.js"></script><p>$(function () { // 表示页面加载完成 之后，相当 window.onload = function () {}<br>var $btnObj = $(“#btnId”); // 表示按 id 查询标签对象<br>$btnObj.click(function () { // 绑定单击事件<br>alert(“jQuery 的单击事件”);<br>});<br>});</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line">$ 是 jQuery 的核心函数，能完成 jQuery 的很多功能。$()就是调用$这个函数1、传入参数为 [ 函数 ] 时：</span><br><span class="line">表示页面加载完成之后。相当于 window.onload = function(){}</span><br><span class="line">2、传入参数为 [ HTML 字符串 ] 时：</span><br><span class="line">会对我们创建这个 html 标签对象</span><br><span class="line">3、传入参数为 [ 选择器字符串 ] 时：</span><br><span class="line">$(“#id 属性值”); id 选择器，根据 id 查询标签对象</span><br><span class="line">$(“标签名”); 标签名选择器，根据指定的标签名查询标签对象</span><br><span class="line">$(“.class 属性值”); 类型选择器，可以根据 class 属性查询标签对象</span><br><span class="line">4、传入参数为 [ DOM 对象 ] 时：</span><br><span class="line">会把这个 dom 对象转换为 jQuery 对象</span><br><span class="line">jQuery 对象的本质是什么？</span><br><span class="line">jQuery 对象是 dom 对象的数组 + jQuery 提供的一系列功能函数。</span><br><span class="line"></span><br><span class="line">1、dom 对象转化为 jQuery 对象（*重点）</span><br><span class="line">1、先有 DOM 对象</span><br><span class="line">2、$( DOM 对象 ) 就可以转换成为 jQuery 对象</span><br><span class="line">2、jQuery 对象转为 dom 对象（*重点）</span><br><span class="line">1、先有 jQuery 对象</span><br><span class="line">2、jQuery 对象[下标]取出相应的 DOM 对象</span><br></pre></td></tr></tbody></table></figure><p><strong>Jquery选择器：</strong></p><p>基本选择器、层级选择器、过滤选择器（基本过滤器、内容过滤器、属性过滤器、表单过滤器、表单对象属性过滤器）</p><p><strong>Jquery的属性操作：</strong></p><p>html() 它可以设置和获取起始标签和结束标签中的内容。 跟 dom 属性 innerHTML 一样。</p><p> text() 它可以设置和获取起始标签和结束标签中的文本。 跟 dom 属性 innerText 一样。</p><p> val() 它可以设置和获取表单项的 value 属性值。 跟 dom 属性 value 一样</p><p>attr() 可以设置和获取属性的值，不推荐操作 checked、readOnly、selected、disabled 等等 attr 方法还可以操作非标准的属性。比如自定义属性：abc,bbj </p><p>prop() 可以设置和获取属性的值,只推荐操作 checked、readOnly、selected、disabled 等等</p><p><em><strong>jQuery 事件操作：</strong></em>**</p><p>$( function(){} ); 和 window.onload = function(){} 的区别？</p><p><strong>他们分别是在什么时候触发？</strong> 1、jQuery 的页面加载完成之后是浏览器的内核解析完页面的标签创建好 DOM 对象之后就会马上执行。 2、原生 js 的页面加载完成之后，除了要等浏览器内核解析完标签创建好 DOM 对象，还要等标签显示时需要的内容加载 完成。</p><p><strong>他们触发的顺序？</strong> 1、jQuery 页面加载完成之后先执行 2、原生 js 的页面加载完成之后</p><p><strong>他们执行的次数？</strong> 1、原生 js 的页面加载完成之后，只会执行最后一次的赋值函数。 2、jQuery 的页面加载完成之后是全部把注册的 function 函数，依次顺序全部执行。</p><h2 id="2-XML、Tomcat"><a href="#2-XML、Tomcat" class="headerlink" title="2.XML、Tomcat"></a>2.XML、Tomcat</h2><p><strong>什么是 xml？</strong></p><p> <strong>xml 是可扩展的标记性语言。</strong></p><p><strong>xml 的主要作用有：</strong></p><p> 1、用来保存数据，而且这些数据具有自我描述性</p><p> 2、它还可以做为项目或者模块的配置文件 </p><p>3、还可以做为网络传输数据的格式（现在 JSON 为主）。</p><p><strong>xml 语法？</strong></p><ol><li>文档声明                                           <!--?xml version="1.0" encoding="UTF-8?--></li><li>元素（标签） </li><li>xml 属性 </li><li>xml 注释 </li><li>文本区域（CDATA 区）</li></ol><p><strong>xml 解析技术：</strong>DOM 和 Sax </p><p><strong>dom4j 解析技术：</strong></p><p>第一步： 先加载 xml 文件创建 Document 对象   </p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">SAXReader reader = new SAXReader(); </span><br><span class="line">Document document = reader.read("src/books.xml");</span><br></pre></td></tr></tbody></table></figure><p>第二步：通过 Document 对象拿到根元素对象      </p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">Element root = document.getRootElement();</span><br></pre></td></tr></tbody></table></figure><p>第三步：通过根元素.elelemts(标签名); 可以返回一个集合，这个集合里放着。所有你指定的标签名的元素对象 </p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">List&lt;Element&gt; books = root.elements("book");</span><br></pre></td></tr></tbody></table></figure><p>第四步：找到你想要修改、删除的子元素，进行相应在的操作 </p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">for (Element book : books) {</span><br><span class="line">// 测试</span><br><span class="line">// System.out.println(book.asXML());</span><br><span class="line">// 拿到 book 下面的 name 元素对象</span><br><span class="line">Element nameElement = book.element("name");</span><br><span class="line">// 拿到 book 下面的 price 元素对象</span><br><span class="line">Element priceElement = book.element("price");</span><br><span class="line">// 拿到 book 下面的 author 元素对象</span><br><span class="line">Element authorElement = book.element("author");</span><br><span class="line">// 再通过 getText() 方法拿到起始标签和结束标签之间的文本内容</span><br><span class="line">System.out.println("书名" + nameElement.getText() + " , 价格:"</span><br><span class="line">+ priceElement.getText() + ", 作者：" + authorElement.getText());</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>第五步，保存到硬盘上</p><p><strong>什么是 JavaWeb</strong> ？</p><p>JavaWeb 是指，所有通过 Java 语言编写可以通过浏览器访问的程序的总称，叫 JavaWeb。 JavaWeb 是基于请求和响应来开发的</p><p><strong>web 资源按实现的技术和呈现的效果的不同，又分为静态资源和动态资源两种。</strong></p><p> 静态资源： html、css、js、txt、mp4 视频 , jpg 图片 </p><p>动态资源： jsp 页面、Servlet 程序</p><h2 id="3-Servlet"><a href="#3-Servlet" class="headerlink" title="3.Servlet"></a><strong>3.Servlet</strong></h2><p><strong>什么是 Servlet？</strong></p><p>1、Servlet 是 JavaEE 规范之一。规范就是<strong>接口</strong> </p><p>2、Servlet 就 JavaWeb 三大组件之一。三大组件分别是：Servlet 程序、Filter 过滤器、Listener 监听器。 </p><p>3、Servlet 是运行在服务器上的一个 java 小程序（server applet），它可以接收客户端发送过来的请求，并响应数据给客户端。</p><p><strong>手动实现 Servlet 程序</strong> </p><p>1、编写一个类去实现 Servlet 接口</p><p> 2、实现 service 方法，处理请求，并响应数据 </p><p>3、到 web.xml 中去配置 servlet 程序的访问地址</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line">&lt;!-- servlet 标签给 Tomcat 配置 Servlet 程序 --&gt;</span><br><span class="line">&lt;servlet&gt;</span><br><span class="line">&lt;!--servlet-name 标签 Servlet 程序起一个别名（一般是类名） --&gt;</span><br><span class="line">&lt;servlet-name&gt;HelloServlet&lt;/servlet-name&gt;</span><br><span class="line">&lt;!--servlet-class 是 Servlet 程序的全类名--&gt;</span><br><span class="line">&lt;servlet-class&gt;com.atguigu.servlet.HelloServlet&lt;/servlet-class&gt;</span><br><span class="line">&lt;/servlet&gt;</span><br><span class="line">&lt;!--servlet-mapping 标签给 servlet 程序配置访问地址--&gt;</span><br><span class="line">&lt;servlet-mapping&gt;</span><br><span class="line">&lt;!--servlet-name 标签的作用是告诉服务器，我当前配置的地址给哪个 Servlet 程序使用--&gt;</span><br><span class="line">&lt;servlet-name&gt;HelloServlet&lt;/servlet-name&gt;</span><br><span class="line">&lt;!--url-pattern 标签配置访问地址 &lt;br/&gt;</span><br><span class="line">/ 斜杠在服务器解析的时候，表示地址为：http://ip:port/工程路径 &lt;br/&gt;</span><br><span class="line">/hello 表示地址为：http://ip:port/工程路径/hello &lt;br/&gt;</span><br><span class="line">--&gt;</span><br><span class="line">&lt;url-pattern&gt;/hello&lt;/url-pattern&gt;</span><br><span class="line">&lt;/servlet-mapping&gt;</span><br></pre></td></tr></tbody></table></figure><p><strong>Servlet 的生命周期？</strong></p><p>1、执行 Servlet 构造器方法 </p><p>2、执行 init 初始化方法 </p><p>第一、二步，是在第一次访问，的时候创建 Servlet 程序会调用。 </p><p>3、执行 service 方法 </p><p>第三步，每次访问都会调用。 </p><p>4、执行 destroy 销毁方法 </p><p>第四步，在 web 工程停止的时候调用</p><p><strong>通过继承 HttpServlet 实现 Servlet程序？</strong></p><p>1、编写一个类去继承 HttpServlet 类<br>2、根据业务需要重写 doGet 或 doPost 方法<br>3、到 web.xml 中的配置 Servlet 程序的访问地址</p><p><strong>ServletConfig 类的三大作用？</strong></p><p>1、可以获取 Servlet 程序的别名 servlet-name 的值         servletConfig.getServletName()<br>2、获取初始化参数 init-param                                        servletConfig.getInitParameter(“username”)<br>3、获取 ServletContext 对象                                                 servletConfig.getServletContext()</p><p><strong>什么是 ServletContex？</strong></p><p>1、ServletContext 是一个接口，它表示 Servlet 上下文对象<br>2、一个 web 工程，只有一个 ServletContext 对象实例。<br>3、ServletContext 对象是一个域对象。<br>4、ServletContext 是在 web 工程部署启动的时候创建。在 web 工程停止的时候</p><p><strong>ServletContext 类的四个作用？</strong></p><p>1、获取 web.xml 中配置的上下文参数 context-param      context.getInitParameter(“username”)</p><!--context-param 是上下文参数(它属于整个 web 工程)--><p>2、获取当前的工程路径，格式: /工程路径                           context.getContextPath()<br>3、获取工程部署后在服务器硬盘上的绝对路径                      context.getRealPath(“/“)<br>4、像 Map 一样存取数据                                                          context.getAttribute(“key1”)</p><p><strong>HttpServletRequest 类有什么作用？</strong></p><p>每次只要有请求进入 Tomcat 服务器，Tomcat 服务器就会把请求过来的 HTTP 协议信息解析好封装到 Request 对象中。<br>然后传递到 service 方法（doGet 和 doPost）中给我们使用。我们可以通过 HttpServletRequest 对象，获取到所有请求的<br>信息。</p><p><strong>HttpServletRequest 类的常用方法？</strong><br>i. getRequestURI() 获取请求的资源路径<br>ii. getRequestURL() 获取请求的统一资源定位符（绝对路径）<br>iii. getRemoteHost() 获取客户端的 ip 地址<br>iv. getHeader() 获取请求头<br>v. getParameter() 获取请求的参数<br>vi. getParameterValues() 获取请求的参数（多个值的时候使用）<br>vii. getMethod() 获取请求的方式 GET 或 POST<br>viii. setAttribute(key, value); 设置域数据<br>ix. getAttribute(key); 获取域数据<br>x. getRequestDispatcher() 获取请求转发对象</p><p><strong>请求转发是指，服务器收到请求后，从一次资源跳转到另一个资源的操作叫请求转发。</strong></p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">RequestDispatcher requestDispatcher = req.getRequestDispatcher("/servlet2");</span><br><span class="line">// RequestDispatcher requestDispatcher = req.getRequestDispatcher("http://www.baidu.com");</span><br><span class="line">// 走向 Sevlet2（柜台 2）</span><br><span class="line">requestDispatcher.forward(req,resp);</span><br></pre></td></tr></tbody></table></figure><p><img src="C:\Users\Javan\AppData\Roaming\Typora\typora-user-images\image-20210327111833808.png" alt="image-20210327111833808"></p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">&lt;!DOCTYPE html&gt;</span><br><span class="line">&lt;html lang="zh_CN"&gt;</span><br><span class="line">&lt;head&gt;</span><br><span class="line">&lt;meta charset="UTF-8"&gt;</span><br><span class="line">&lt;title&gt;Title&lt;/title&gt;</span><br><span class="line">&lt;!--base 标签设置页面相对路径工作时参照的地址</span><br><span class="line">href 属性就是参数的地址值   后缀一定要以  / 结尾</span><br><span class="line">--&gt;</span><br><span class="line">&lt;base href="http://localhost:8080/07_servlet/a/b/"&gt;</span><br><span class="line">&lt;/head&gt;</span><br><span class="line">&lt;body&gt;</span><br><span class="line">这是 a 下的 b 下的 c.html 页面&lt;br/&gt;</span><br><span class="line">&lt;a href="../../index.html"&gt;跳回首页&lt;/a&gt;&lt;br/&gt;</span><br><span class="line">&lt;/body&gt;</span><br><span class="line">&lt;/html&gt;</span><br></pre></td></tr></tbody></table></figure><p><strong>web 中 / 斜杠的不同意义？</strong></p><p>在 web 中 / 斜杠 是一种绝对路径。<br>/ 斜杠 如果被<strong>浏览器</strong>解析，得到的地址是：<a href="http://ip:port/">http://ip:port/</a><br><a href="/">斜杠</a><br>/ 斜杠 如果被<strong>服务器</strong>解析，得到的地址是：<a href="http://ip:port/工程路径">http://ip:port/工程路径</a><br>1、<url-pattern>/servlet1</url-pattern><br>2、servletContext.getRealPath(“/”);<br>3、request.getRequestDispatcher(“/”);<br>特殊情况： response.sendRediect(“/”); 把斜杠发送给浏览器解析。得到 <a href="http://ip:port/">http://ip:port/</a></p><p><strong>HttpServletResponse 类的作用</strong>？</p><p>HttpServletResponse 类和 HttpServletRequest 类一样。每次请求进来，Tomcat 服务器都会创建一个 Response 对象传 递给 Servlet 程序去使用。HttpServletRequest 表示请求过来的信息，HttpServletResponse 表示所有响应的信息， 我们如果需要设置返回给客户端的信息，都可以通过 HttpServletResponse 对象来进行</p><p><strong>两个输出流的说明。</strong></p><p> 字节流 getOutputStream(); 常用于下载（传递二进制数据） </p><p>字符流 getWriter(); 常用于回传字符串（常用） </p><p>两个流同时只能使用一个。 使用了字节流，就不能再使用字符流，反之亦然，否则就会报错。</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">public class ResponseIOServlet extends HttpServlet {</span><br><span class="line">@Override</span><br><span class="line">protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException,</span><br><span class="line">IOException {</span><br><span class="line">// 要求 ： 往客户端回传 字符串 数据。</span><br><span class="line">PrintWriter writer = resp.getWriter();</span><br><span class="line">writer.write("response's content!!!");</span><br><span class="line">}</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><strong>请求重定向，是指客户端给服务器发请求，然后服务器告诉客户端说。我给你一些地址。你去新地址访问。叫请求</strong><br><strong>重定向（因为之前的地址可能已经被废弃）。</strong></p><p><img src="C:\Users\Javan\AppData\Roaming\Typora\typora-user-images\image-20210327113158366.png" alt="image-20210327113158366"></p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">resp.sendRedirect("http://localhost:8080");</span><br></pre></td></tr></tbody></table></figure><h2 id="4-JSP"><a href="#4-JSP" class="headerlink" title="4.JSP"></a>4.JSP</h2><p><strong>jsp 的全换是 java server pages。Java 的服务器页面。</strong></p><p> <strong>jsp 的主要作用是代替 Servlet 程序回传 html 页面的数据。</strong></p><p><strong>因为 Servlet 程序回传 html 页面数据是一件非常繁锁的事情。开发成本和维护成本都极高。</strong></p><p><strong>jsp 的本质是什么？</strong></p><p>jsp 页面本质上是一个 Servlet 程序。</p><p><strong>jsp 的三种语法：</strong></p><p><strong>a)jsp 头部的 page 指令</strong></p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">&lt;%@ page contentType="text/html;charset=UTF-8" language="java" %&gt;</span><br></pre></td></tr></tbody></table></figure><p><strong>b)jsp 中的常用脚本</strong></p><p>表达式脚本（常用） 表达式脚本的格式是：&lt;%=表达式%&gt; 表达式脚本的作用是：在 jsp 页面上输出数据</p><p>代码脚本的格式是： &lt;% java 语句 %&gt; 代码脚本的作用是：可以在 jsp 页面中，编写我们自己需要的功能（写的是 java 语句）。</p><p><strong>c)jsp 中的三种注释</strong></p><p>i. html 注释 、ii. java 注释 、iii. jsp 注释</p><p><strong>jsp 四大域对象</strong></p><p>四个域对象分别是：<br>pageContext (PageContextImpl 类)                              当前 jsp 页面范围内有效<br>request (HttpServletRequest 类)、                              一次请求内有效<br>session (HttpSession 类)、                                             一个会话范围内有效（打开浏览器访问服务器，直到关闭浏览器）<br>application (ServletContext 类)                                 整个 web 工程范围内都有效（只要 web 工程不停止，数据都在）<br>域对象是可以像 Map 一样存取数据的对象。四个域对象功能一样。不同的是它们对数据的存取范围。<br>虽然四个域对象都可以存取数据。在使用上它们是有优先顺序的。<br>四个域在使用的时候，优先顺序分别是，他们从小到大的范围的顺序。<br>pageContext ====&gt;&gt;&gt; request ====&gt;&gt;&gt; session ====&gt;&gt;&gt; application</p><h2 id="5-Listener-监听器"><a href="#5-Listener-监听器" class="headerlink" title="5.Listener 监听器"></a>5.Listener 监听器</h2><p>1、Listener 监听器它是 JavaWeb 的三大组件之一。JavaWeb 的三大组件分别是：Servlet 程序、Filter 过滤器、Listener 监<br>听器。<br>2、Listener 它是 JavaEE 的规范，就是接口<br>3、监听器的作用是，监听某种事物的变化。然后通过回调函数，反馈给客户（程序）去做一些相应的处理。</p><p><strong>ServletContextListener 监听器</strong></p><p>ServletContextListener 它可以监听 ServletContext 对象的创建和销毁。 </p><p>ServletContext 对象在 web 工程启动的时候创建，在 web 工程停止的时候销毁。 监听到创建和销毁之后都会分别调用 ServletContextListener 监听器的方法反馈。</p><p><strong>如何使用 ServletContextListener 监听器监听 ServletContext 对象。</strong><br>使用步骤如下：<br>1、编写一个类去实现 ServletContextListener<br>2、实现其两个回调方法     contextInitialized（）                contextDestroyed（）<br>3、到 web.xml 中去配置监听器</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">public class MyServletContextListenerImpl implements ServletContextListener {</span><br><span class="line">@Override</span><br><span class="line">public void contextInitialized(ServletContextEvent sce) {</span><br><span class="line">System.out.println("ServletContext 对象被创建了");</span><br><span class="line">}</span><br><span class="line">@Override</span><br><span class="line">public void contextDestroyed(ServletContextEvent sce) {</span><br><span class="line">System.out.println("ServletContext 对象被销毁了");</span><br><span class="line">}</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>web.xml 中的配置</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">&lt;!--配置监听器--&gt;</span><br><span class="line">&lt;listener&gt;</span><br><span class="line">&lt;listener-class&gt;com.atguigu.listener.MyServletContextListenerImpl&lt;/listener-class&gt;</span><br><span class="line">&lt;/listener&gt;</span><br></pre></td></tr></tbody></table></figure><h2 id="6-EL表达式、JSTL标签库"><a href="#6-EL表达式、JSTL标签库" class="headerlink" title="6.EL表达式、JSTL标签库"></a><strong>6.EL表达式、JSTL标签库</strong></h2><p>EL 表达式的全称是：Expression Language。是表达式语言。<br>EL 表达式的什么作用：EL 表达式主要是代替 jsp 页面中的表达式脚本在 jsp 页面中进行数据的输出。<br>因为 EL 表达式在输出数据的时候，要比 jsp 的表达式脚本要简洁很多</p><p><strong>EL 表达式的格式是：${表达式}</strong><br>EL 表达式在输出 null 值的时候，输出的是空串。jsp 表达式脚本输出 null 值的时候，输出的是 null</p><p><img src="C:\Users\Javan\AppData\Roaming\Typora\typora-user-images\image-20210327194844288.png" alt="image-20210327194844288"></p><p><strong>JSTL 标签库：</strong></p><p>JSTL 标签库 全称是指 JSP Standard Tag Library JSP 标准标签库。是一个不断完善的开放源代码的 JSP 标 签库。</p><p> EL 表达式主要是为了替换 jsp 中的表达式脚本，而JSTL标签库则是为了替换代码脚本。这样使得整个 jsp 页面 变得更佳简洁。</p><p><strong>JSTL 标签库的使用步骤</strong>：<br>1、先导入 jstl 标签库的 jar 包。<br>taglibs-standard-impl-1.2.1.jar<br>taglibs-standard-spec-1.2.1.jar<br>2、第二步，使用 taglib 指令引入标签库。<br>&lt;%@ taglib prefix=”c” uri=”<a href="http://java.sun.com/jsp/jstl/core&quot;">http://java.sun.com/jsp/jstl/core"</a> %&gt;</p><p>core 核心库使用：用的时候再百度</p><h2 id="7-Cookie和Session"><a href="#7-Cookie和Session" class="headerlink" title="7.Cookie和Session"></a>7.Cookie和Session</h2><p><strong>什么是 Cookie?</strong><br>1、Cookie 翻译过来是饼干的意思。<br>2、Cookie 是服务器通知客户端保存键值对的一种技术。<br>3、客户端有了 Cookie 后，每次请求都发送给服务器。<br>4、每个 Cookie 的大小不能超过 4kb</p><p><strong>如何创建 Cookie？</strong></p><p><img src="C:\Users\Javan\AppData\Roaming\Typora\typora-user-images\image-20210327195502261.png" alt="image-20210327195502261"></p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">protected void createCookie(HttpServletRequest req, HttpServletResponse resp) throws ServletException,</span><br><span class="line">IOException {</span><br><span class="line">//1 创建 Cookie 对象Cookie cookie = new Cookie("key4", "value4");</span><br><span class="line">//2 通知客户端保存 Cookie</span><br><span class="line">resp.addCookie(cookie);</span><br><span class="line">//1 创建 Cookie 对象</span><br><span class="line">Cookie cookie1 = new Cookie("key5", "value5");</span><br><span class="line">//2 通知客户端保存 Cookie</span><br><span class="line">resp.addCookie(cookie1);</span><br><span class="line">resp.getWriter().write("Cookie 创建成功");</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><strong>服务器如何获取 Cookie？</strong></p><p>服务器获取客户端的 Cookie 只需要一行代码：req.getCookies():Cookie[]</p><p><img src="C:\Users\Javan\AppData\Roaming\Typora\typora-user-images\image-20210327195613656.png" alt="image-20210327195613656"></p><p><strong>Cookie 值的修改？</strong></p><p>方案一：<br>1、先创建一个要修改的同名（指的就是 key）的 Cookie 对象<br>2、在构造器，同时赋于新的 Cookie 值。<br>3、调用 response.addCookie( Cookie）</p><p>方案二：<br>1、先查找到需要修改的 Cookie 对象<br>2、调用 setValue()方法赋于新的 Cookie 值。<br>3、调用 response.addCookie()通知客户端保存修改</p><p><strong>Cookie 生命控制？</strong></p><p>Cookie 的生命控制指的是如何管理 Cookie 什么时候被销毁（删除）<br>setMaxAge()<br>正数，表示在指定的秒数后过期<br>负数，表示浏览器一关，Cookie 就会被删除（默认值是-1）<br>零，表示马上删除 Cookie</p><p><strong>什么是 Session 会话？</strong></p><p>1、Session 就一个接口（HttpSession）。<br>2、Session 就是会话。它是用来维护一个客户端和服务器之间关联的一种技术。<br>3、每个客户端都有自己的一个 Session 会话。<br>4、Session 会话中，我们经常用来保存用户登录之后的信息。</p><p>如何创建和获取 Session。它们的 API 是一样的。<br>request.getSession()<br>第一次调用是：创建 Session 会话<br>之后调用都是：获取前面创建好的 Session 会话对象</p><p><strong>Session 生命周期控制？</strong></p><p>public void setMaxInactiveInterval(int interval) 设置 Session 的超时时间（以秒为单位），超过指定的时长，Session<br>就会被销毁。<br>值为正数的时候，设定 Session 的超时时长。<br>负数表示永不超时（极少使用）<br>public int getMaxInactiveInterval()获取 Session 的超时时间<br>public void invalidate() 让当前 Session 会话马上超时无效</p><p><img src="C:\Users\Javan\AppData\Roaming\Typora\typora-user-images\image-20210327200424416.png" alt="image-20210327200424416"></p><p><strong>总结：</strong></p><p>1，session 在服务器端，cookie 在客户端（浏览器）<br> 2，session 默认被存在在服务器的一个文件里（不是内存）<br> 3，session 的运行依赖 session id，而 session id 是存在 cookie 中的，也就是说，如果浏览器禁用了 cookie ，同时 session 也会失效（但是可以通过其它方式实现，比如在 url 中传递 session_id）<br> 4，session 可以放在 文件、数据库、或内存中都可以。<br> 5，用户验证这种场合一般会用 session </p><p>因此，维持一个会话的核心就是客户端的唯一标识，即 session id。</p><p>Session是在服务端保存的一个数据结构，用来跟踪用户的状态，这个数据可以保存在集群、数据库、文件中；<br>Cookie是客户端保存用户信息的一种机制，用来记录用户的一些信息，也是实现Session的一种方式。</p><h2 id="8-Filter过滤器"><a href="#8-Filter过滤器" class="headerlink" title="8.Filter过滤器"></a><strong>8.Filter过滤器</strong></h2><p>1、Filter 过滤器它是 JavaWeb 的三大组件之一。三大组件分别是：Servlet 程序、Listener 监听器、Filter 过滤器<br>2、Filter 过滤器它是 JavaEE 的规范。也就是接口<br>3、Filter 过滤器它的作用是：拦截请求，过滤响应。</p><p>拦截请求常见的应用场景有：<br>1、权限检查<br>2、日记操作<br>3、事务管理<br>……等等</p><p><strong>Filter 过滤器的使用步骤：</strong><br>1、编写一个类去实现 Filter 接口<br>2、实现过滤方法 doFilter()<br>3、到 web.xml 中去配置 Filter 的拦截路径</p><p><img src="C:\Users\Javan\AppData\Roaming\Typora\typora-user-images\image-20210327201333684.png" alt="image-20210327201333684"></p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line">public class AdminFilter implements Filter {</span><br><span class="line">/**</span><br><span class="line">* doFilter 方法，专门用于拦截请求。可以做权限检查</span><br><span class="line">*/</span><br><span class="line">@Override</span><br><span class="line">public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain</span><br><span class="line">filterChain) throws IOException, ServletException {</span><br><span class="line">HttpServletRequest httpServletRequest = (HttpServletRequest) servletRequest;</span><br><span class="line">HttpSession session = httpServletRequest.getSession();</span><br><span class="line">Object user = session.getAttribute("user");</span><br><span class="line">// 如果等于 null，说明还没有登录</span><br><span class="line">if (user == null) {</span><br><span class="line">servletRequest.getRequestDispatcher("/login.jsp").forward(servletRequest,servletResponse);</span><br><span class="line">return;</span><br><span class="line">} else {</span><br><span class="line">// 让程序继续往下访问用户的目标资源</span><br><span class="line">filterChain.doFilter(servletRequest,servletResponse);</span><br><span class="line">}</span><br><span class="line">}</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>web.xml 中的配置：</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line">&lt;!--filter 标签用于配置一个 Filter 过滤器--&gt;</span><br><span class="line">&lt;filter&gt;</span><br><span class="line">&lt;!--给 filter 起一个别名--&gt;</span><br><span class="line">&lt;filter-name&gt;AdminFilter&lt;/filter-name&gt;</span><br><span class="line">&lt;!--配置 filter 的全类名--&gt;</span><br><span class="line">&lt;filter-class&gt;com.atguigu.filter.AdminFilter&lt;/filter-class&gt;</span><br><span class="line">&lt;/filter&gt;&lt;!--filter-mapping 配置 Filter 过滤器的拦截路径--&gt;</span><br><span class="line">&lt;filter-mapping&gt;</span><br><span class="line">&lt;!--filter-name 表示当前的拦截路径给哪个 filter 使用--&gt;</span><br><span class="line">&lt;filter-name&gt;AdminFilter&lt;/filter-name&gt;</span><br><span class="line">&lt;!--url-pattern 配置拦截路径</span><br><span class="line">/ 表示请求地址为：http://ip:port/工程路径/ 映射到 IDEA 的 web 目录</span><br><span class="line">/admin/* 表示请求地址为：http://ip:port/工程路径/admin/*</span><br><span class="line">--&gt;</span><br><span class="line">&lt;url-pattern&gt;/admin/*&lt;/url-pattern&gt;</span><br><span class="line">&lt;/filter-mapping&gt;</span><br></pre></td></tr></tbody></table></figure><p><strong>Filter 的生命周期：</strong></p><p>Filter 的生命周期包含几个方法<br>1、构造器方法<br>2、init 初始化方法<br>第 1，2 步，在 web 工程启动的时候执行（Filter 已经创建）<br>3、doFilter 过滤方法<br>第 3 步，每次拦截到请求，就会执行<br>4、destroy 销毁<br>第 4 步，停止 web 工程的时候，就会执行（停止 web 工程，也会销毁 Filter 过滤器）</p><p><strong>FilterConfig 类</strong></p><p>FilterConfig 类见名知义，它是 Filter 过滤器的配置文件类。<br>Tomcat 每次创建 Filter 的时候，也会同时创建一个 FilterConfig 类，这里包含了 Filter 配置文件的配置信息。<br>FilterConfig 类的作用是获取 filter 过滤器的配置内容<br>1、获取 Filter 的名称 filter-name 的内容<br>2、获取在 Filter 中配置的 init-param 初始化参数<br>3、获取 ServletContext 对象</p><h2 id="9-JSON、AJAX"><a href="#9-JSON、AJAX" class="headerlink" title="9.JSON、AJAX"></a>9.JSON、AJAX</h2><p>JSON (JavaScript Object Notation) 是一种轻量级的数据交换格式。轻量级指的是跟 xml 做比较。 数据交换指的是客户端和服务器之间业务数据的传递格式。</p><p>json 是由键值对组成，并且由花括号（大括号）包围。每个键由引号引起来，键和值之间使用冒号进行分隔， 多组键值对之间进行逗号进行分隔。</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line">var jsonObj = {</span><br><span class="line">"key1":12,</span><br><span class="line">"key2":"abc",</span><br><span class="line">"key3":true,</span><br><span class="line">"key4":[11,"arr",false],</span><br><span class="line">"key5":{</span><br><span class="line">"key5_1" : 551,</span><br><span class="line">"key5_2" : "key5_2_value"</span><br><span class="line">},</span><br><span class="line">"key6":[{</span><br><span class="line">"key6_1_1":6611,</span><br><span class="line">"key6_1_2":"key6_1_2_value"},{</span><br><span class="line">"key6_2_1":6621,</span><br><span class="line">"key6_2_2":"key6_2_2_value"</span><br><span class="line">}]</span><br><span class="line">};</span><br></pre></td></tr></tbody></table></figure><p>json 本身是一个对象。 json 中的 key 我们可以理解为是对象中的一个属性。 json 中的 key 访问就跟访问对象的属性一样： json 对象.key</p><p>json 的存在有两种形式。<br>一种是：对象的形式存在，我们叫它 json 对象。<br>一种是：字符串的形式存在，我们叫它 json 字符串。<br><strong>一般我们要操作 json 中的数据的时候，需要 json 对象的格式。</strong><br><strong>一般我们要在客户端和服务器之间进行数据交换的时候，使用 json 字符串。</strong><br>JSON.stringify() 把 json 对象转换成为 json 字符串<br>JSON.parse() 把 json 字符串转换成为 json 对象</p><p><strong>JSON 在 java 中的使用：</strong></p><p>javaBean 和 json 的互转：<strong>tojson（） 和 fromjson（）的使用</strong></p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">@Test</span><br><span class="line">public void test1(){</span><br><span class="line">Person person = new Person(1,"国哥好帅!");</span><br><span class="line">// 创建 Gson 对象实例</span><br><span class="line">Gson gson = new Gson();</span><br><span class="line">// toJson 方法可以把 java 对象转换成为 json 字符串</span><br><span class="line">String personJsonString = gson.toJson(person);</span><br><span class="line">System.out.println(personJsonString);</span><br><span class="line">// fromJson 把 json 字符串转换回 Java 对象</span><br><span class="line">// 第一个参数是 json 字符串</span><br><span class="line">// 第二个参数是转换回去的 Java 对象类型</span><br><span class="line">Person person1 = gson.fromJson(personJsonString, Person.class);</span><br><span class="line">System.out.println(person1);</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p>List 和 json 的互转：<strong>tojson（） 和 fromjson（）的使用</strong></p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">@Test</span><br><span class="line">public void test2() {</span><br><span class="line">List&lt;Person&gt; personList = new ArrayList&lt;&gt;();</span><br><span class="line">personList.add(new Person(1, "国哥"));</span><br><span class="line">personList.add(new Person(2, "康师傅"));</span><br><span class="line">Gson gson = new Gson();</span><br><span class="line">// 把 List 转换为 json 字符串</span><br><span class="line">String personListJsonString = gson.toJson(personList);</span><br><span class="line">System.out.println(personListJsonString);</span><br><span class="line">//PersonListType类继承了TypeToken&lt;ArrayList&lt;Person&gt;&gt;</span><br><span class="line">List&lt;Person&gt; list = gson.fromJson(personListJsonString, new PersonListType().getType());</span><br><span class="line">System.out.println(list);</span><br><span class="line">Person person = list.get(0);</span><br><span class="line">System.out.println(person);</span><br><span class="line">}</span><br></pre></td></tr></tbody></table></figure><p><strong>AJAX请求：</strong></p><p>AJAX 即“Asynchronous Javascript And XML”（异步 JavaScript 和 XML），是指一种创建交互式网页应用的网页开发<br>技术。<br>ajax 是一种浏览器通过 js 异步发起请求，局部更新页面的技术。<br>Ajax 请求的局部更新，浏览器地址栏不会发生变化<br>局部更新不会舍弃原来页面的内容</p><p><strong>jQuery 中的 AJAX 请求</strong></p><p>$.ajax 方法 </p><p>url 表示请求的地址</p><p>type 表示请求的类型 </p><p>​            GET 或 POST 请求 </p><p>data 表示发送给服务器的数据 </p><p>​            格式有两种： 一：name=value&amp;name=value 二：{key:value}</p><p> success 请求成功，响应的回调函数 </p><p>dataType 响应的数据类型 常用的数据类型有： </p><p>​            text 表示纯文本 xml 表示 xml 数据 json 表示 json 对象</p><figure class="highlight plain"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">$("#ajaxBtn").click(function(){</span><br><span class="line">$.ajax({</span><br><span class="line">url:"http://localhost:8080/16_json_ajax_i18n/ajaxServlet",</span><br><span class="line">// data:"action=jQueryAjax",</span><br><span class="line">data:{action:"jQueryAjax"},</span><br><span class="line">type:"GET",</span><br><span class="line">success:function (data) {</span><br><span class="line">// alert("服务器返回的数据是：" + data);</span><br><span class="line">// var jsonObj = JSON.parse(data);</span><br><span class="line">$("#msg").html("编号：" + data.id + " , 姓名：" + data.name);</span><br><span class="line">},</span><br><span class="line">dataType : "json"</span><br><span class="line">});</span><br><span class="line">});</span><br></pre></td></tr></tbody></table></figure>]]></content>
      
      
      
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    <entry>
      <title>Hello World</title>
      <link href="/javanblog/2021/04/23/hello-world/"/>
      <url>/javanblog/2021/04/23/hello-world/</url>
      
        <content type="html"><![CDATA[<p>Welcome to <a href="https://hexo.io/">Hexo</a>! This is your very first post. Check <a href="https://hexo.io/docs/">documentation</a> for more info. If you get any problems when using Hexo, you can find the answer in <a href="https://hexo.io/docs/troubleshooting.html">troubleshooting</a> or you can ask me on <a href="https://github.com/hexojs/hexo/issues">GitHub</a>.</p><h2 id="Quick-Start"><a href="#Quick-Start" class="headerlink" title="Quick Start"></a>Quick Start</h2><h3 id="Create-a-new-post"><a href="#Create-a-new-post" class="headerlink" title="Create a new post"></a>Create a new post</h3><figure class="highlight bash"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo new <span class="string">"My New Post"</span></span><br></pre></td></tr></tbody></table></figure><p>More info: <a href="https://hexo.io/docs/writing.html">Writing</a></p><h3 id="Run-server"><a href="#Run-server" class="headerlink" title="Run server"></a>Run server</h3><figure class="highlight bash"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo server</span><br></pre></td></tr></tbody></table></figure><p>More info: <a href="https://hexo.io/docs/server.html">Server</a></p><h3 id="Generate-static-files"><a href="#Generate-static-files" class="headerlink" title="Generate static files"></a>Generate static files</h3><figure class="highlight bash"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo generate</span><br></pre></td></tr></tbody></table></figure><p>More info: <a href="https://hexo.io/docs/generating.html">Generating</a></p><h3 id="Deploy-to-remote-sites"><a href="#Deploy-to-remote-sites" class="headerlink" title="Deploy to remote sites"></a>Deploy to remote sites</h3><figure class="highlight bash"><table><tbody><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">$ hexo deploy</span><br></pre></td></tr></tbody></table></figure><p>More info: <a href="https://hexo.io/docs/one-command-deployment.html">Deployment</a></p>]]></content>
      
      
      
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