README-zh.md · baomidou/mybatis-plus4

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[企业版 Mybatis-Mate 高级特性](https://gitee.com/baomidou/mybatis-mate-examples)

https://toscode.gitee.com/fhs-opensource/mybatis-plus-4.0-demo  可以通过此demo学习MP4的新特性。

### maven坐标
因为MP4版本没有正式发布，故没有发布到包米豆的groupid下。 
目前最新版本为4.0.5.
```xml
 <dependency>
 <groupId>com.fhs-opensource</groupId>
 <artifactId>mybatis-plus-annotation</artifactId>
 <version>${fhs.mp.version}</version>
 </dependency>
 <dependency>
 <groupId>com.fhs-opensource</groupId>
 <artifactId>mybatis-plus-advance</artifactId>
 <version>${fhs.mp.version}</version>
 </dependency>
 <dependency>
 <groupId>com.fhs-opensource</groupId>
 <artifactId>mybatis-plus-boot-starter</artifactId>
 <version>${fhs.mp.version}</version>
 <scope>compile</scope>
 </dependency>

<dependency>
 <groupId>com.fhs-opensource</groupId>
 <artifactId>mybatis-plus-core</artifactId>
 <version>${fhs.mp.version}</version>
 <scope>compile</scope>
 </dependency>
 <dependency>
 <groupId>com.fhs-opensource</groupId>
 <artifactId>mybatis-plus-extension</artifactId>
 <version>${fhs.mp.version}</version>
 </dependency>
```

### 多表Join支持使用说明
mybatis的多表查询分为2个步骤，1是自定义多表的resultMap,2是写多表查询sql。MP的多表实现也是通过自动生成多表resultMap和自动生成多表查询SQL实现的。    
1、准备2个po
 ```java
@Data
@TableName(value="user",autoResultMap = true)
public class User {

@TableId("user_id")
    private Integer userId;

@TableField("name")
    private String name;

@TableField("age")
    private Integer age;

@TableField("sex")
    private String sex;

//指定这个字段和School 的id字段关联，如果不是和id字段关联可以使用targetFields属性进行关联
    @TableField(value="school_id",target = School.class)
    private Integer schoolId;

//如果是一对多的话使用ONE_TO_MANY并且指定targetClass
    @TableField(relation = Relation.ONE_TO_ONE)
    private School school;
}

```
```java
@Data
@TableName(value="school",autoResultMap = true) //这里设置自动生成resultMap 不需要别的操作
public class School {
    @TableId
    private Integer id;

@TableField("school_name")
    private String schoolName;

@TableField("remark")
    private String remark;
}

```
2、启动join插件(不然返回结果映射会有问题，此插件动态修改resultMap)        
```java
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        interceptor.addInnerInterceptor(new JoinInterceptor());
        return interceptor;
    }
```

3、使用BasicJoinQueryWrapper (为po advance query预留的，不推荐开发者直接使用) 
```java
 BasicJoinQueryWrapper<User> wrapper = new BasicJoinQueryWrapper<>(User.class);
 wrapper.innerJoin(School.class);
 wrapper.eq(new BasicJoinQueryWrapper.ModelProperty(User.class,"schoolId"),1);
 wrapper.select(new BasicJoinQueryWrapper.ModelProperty(User.class,"schoolId"));
 wrapper.select(new BasicJoinQueryWrapper.ModelProperty(User.class,"userId"));
 wrapper.select(new BasicJoinQueryWrapper.ModelProperty(User.class,"name"));
 wrapper.select(new BasicJoinQueryWrapper.ModelProperty(School.class,"schoolName"));
 wrapper.select(new BasicJoinQueryWrapper.ModelProperty(School.class,"id"));
 wrapper.select(new BasicJoinQueryWrapper.ModelProperty(School.class,"remark"));
 mapper.selectList(wrapper);
```
 po advance query写法 ：
 ```java
new User().select(User.SCHOOLID,User.USERID,User.NAME).userId().eq(1).innerJoin(School.class).orgName().like("一").select(School.ID,School.REMARK,School.SCHOOLNAME).list();
```
需要mybatis-plus-advance 依赖：https://gitee.com/baomidou/mybatis-plus-advance

3、使用LambdaJoinQueryWrapper
```java
 LambdaJoinQueryWrapper<User> wrapper = new LambdaJoinQueryWrapper<>(User.class);
 wrapper.eq(User::getSchoolId,1);
 wrapper.innerJoin(School.class).like(School::getSchoolName,"一");
 mapper.selectList(wrapper);
```
### 函数支持
改动：在query接口中添加了selectFun方法，支持用户使用函数来查询字段，目前各类wrapper实现均已支持此查询
```java
 Children selectFun(BaseFuncEnum fun,R alias,R column)
```
1、po上添加接收函数返回的字段
```java
@TableField(exist = false,funField = true) //标记数据库不存在，并且是个函数字段
private Long schoolCount;
```
2、各类wrapper使用
```java
// QueryWrapper
new QueryWrapper<User>().eq("school_id",2).select("school_id").selectFun(DefaultFuncEnum.COUNT,
 "schoolCount").groupBy("school_id")

// LambdaQueryWrapper
new LambdaQueryWrapper<User>().eq(User::getSchoolId,2)
 .select(User::getSchoolId).selectFun(DefaultFuncEnum.COUNT,User::getSchoolCount).groupBy(User::getSchoolId)

// QueryChainWrapper
QueryChainWrapper<User> wrapper = new QueryChainWrapper<User>(mapper);
wrapper.eq("school_id",2).select("school_id").selectFun(DefaultFuncEnum.COUNT,
 "schoolCount").groupBy("school_id").one()
// LambdaQueryChainWrapper
LambdaQueryChainWrapper<User> wrapper = new LambdaQueryChainWrapper<User>(mapper);
wrapper.eq(User::getSchoolId,2) .select(User::getSchoolId).selectFun(DefaultFuncEnum.COUNT,User::getSchoolCount).groupBy(User::getSchoolId).one()

// BasicJoinQueryWrapper
 BasicJoinQueryWrapper<User> wrapper = new BasicJoinQueryWrapper<>(User.class);
wrapper.eq(new BasicJoinQueryWrapper.ModelProperty(User.class,"schoolId"),2);
wrapper.select(new BasicJoinQueryWrapper.ModelProperty(User.class,"schoolId"));
wrapper.selectFun(DefaultFuncEnum.COUNT,new BasicJoinQueryWrapper.ModelProperty(User.class,"schoolCount"));
wrapper.groupBy(new BasicJoinQueryWrapper.ModelProperty(User.class,"schoolId"));

// LambdaJoinQueryWrapper
LambdaJoinQueryWrapper<User> wrapper = new LambdaJoinQueryWrapper<>(User.class);
wrapper.eq(User::getSchoolId,2);
wrapper.select(User::getSchoolId);
wrapper.selectFun(DefaultFuncEnum.COUNT,User::getSchoolCount);
wrapper.groupBy(User::getSchoolId);
```

### 批量插入支持说明
1.目前已经支持的数据库有：mysql,oracle,postgresql,sqlserver
2.序列自增配置：
```java
    /**
     * Postgre 主键生成器
     * @return
     */
    @Bean
    public IKeyGenerator keyGenerator() {
        return new PostgreKeyGenerator(); // oracle和Postgre 序列生成主键都已经支持
    }
    /**
     * 序列自增插件
     */
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
		//需要依赖此拦截器
        interceptor.addInnerInterceptor(new KeyGeneratorInterceptor());
        return interceptor;
    }
```
3.数据库类型配置(也可以配置到@tablename注解里，注解优先于全局配置)
```yaml
mybatis-plus:
  global-config:
    db-config:
      # 数据库类型
      db-type: mysql
```

### 批量修改支持说明
1.目前已经支持的数据库有：mysql,oracle,postgresql
2.已知问题-oracle返回的受影响行数不对

### 前端高级查询API
后端在参数中配置一个QueryFilter<T>,QueryFilter 提供一个asWrapper方法可以把前端的过滤条件包装为一个QueryWrapper
````java
 @PostMapping("list")
 public List<User> filter(@RequestBody QueryFilter<User> filter){
		//注意sex和age是安全字段，就算前端传了也不会拼接这2个字段的过滤条件。
 return mapper.selectList(filter.asWrapper(User.class,"sex","age"));
 }
````
前端按照指定格式传参，即可实现后端不做多余编程前端自由控制过滤条件的效果。
```json
{
 "sorter":[{//排序支持ASC和DESC
 "property":"userId",
 "direction":"DESC"
 }],
 "querys":[{//过滤条件 where sex=男 and (name=张三 or name=李四 )
 "property":"name", // po字段名
 "operator":"=",//操作符 
 "value":"张三",//操作值
 "relation":"OR",//关联关系AND OR
 "group":"nameGroup"//相同的group 外层会加括号
 },
 {
 "property":"name",
 "operator":"=",
 "value":"李四",
 "relation":"OR",
 "group":"nameGroup"
 },{
 "property":"sex", //使用了默认的关联关系AND 以及默认操作符 =
 "value":"男"
 }]
}
```
操作符支持：支持 = > >= < <= like like_l like_r not_like is_null not_null in not_in between not_between 等常见操作
如果是in 等操作 value支持数组传参
本功能暂定在https://gitee.com/baomidou/mybatis-plus-advance 包中

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