# mybatis-plus-join * 支持连表查询的[mybatis-plus](https://gitee.com/baomidou/mybatis-plus) * [演示示例](https://gitee.com/best_handsome/mybatis-plus-join-demo) QQ群:1022221898 [扫码加微信群](https://gitee.com/best_handsome/mybatis-plus-join/blob/master/wx.png) ## 使用方法 [goto wiki](https://gitee.com/best_handsome/mybatis-plus-join/wikis) ## 通用连表wrapper [点击跳转至使用方法](https://gitee.com/best_handsome/mybatis-plus-join/tree/master/src/main/java/com/github/yulichang/common) ### 安装 1. 在项目中添加依赖 ```xml com.github.yulichang mybatis-plus-join 1.1.2 ``` 或者clone代码到本地,执行mvn install,再引入以上依赖

2. 添加配置文件 ```java @Configuration public class MybatisPlusConfig { /** * 启用连表拦截器 */ @Bean public MybatisPlusInterceptor paginationInterceptor() { MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor(); //分页插件 interceptor.addInnerInterceptor(new PaginationInnerInterceptor()); //连表插件 interceptor.addInnerInterceptor(new MPJInterceptor()); //其他mp插件...... return interceptor; } /** * sql注入器 */ @Bean public MPJSqlInjector mySqlInjector() { return new MPJSqlInjector(); } } ``` ### 使用 * mapper继承MPJBaseMapper (必选) * service继承MPJBaseService (可选) * serviceImpl继承MPJBaseServiceImpl (可选) 1. MPJBaseMapper继承BaseMapper,在原有的方法基础上又添加了以下方法: * selectJoinOne 连表查询一条记录对象 * selectJoinList 连表查询返回命中记录对象集合 * selectJoinPage 连表分页查询对象集合 * selectJoinMap 连表查询一条记录返回Map * selectJoinMaps 连表查询返回命中记录Map集合 * selectJoinMapsPage 连表分页查询返回Map集合 2. MPJBaseService 继承了IService,同样添加以上方法 3. MPJBaseServiceImpl 继承了ServiceImpl,同样添加了以上方法 ## 核心类 MPJQueryWrapper,MPJLambdaQueryWrapper和MPJJoinLambdaQueryWrapper |-|MPJQueryWrapper|MPJLambdaQueryWrapper|MPJJoinLambdaQueryWrapper| |---|---|---|---| |select(String)|支持|**支持**|不支持| |select(lambda)|不支持|仅支持主表lambda|所有表lambda| |join(String)|支持|支持|不支持| |join(lambda)|不支持|不支持|支持| |条件String|支持|不支持|不支持| |条件lambda|不支持|仅支持主表lambda|所有表lambda| MPJQueryWrapper相当于mp的QueryWrapper MPJLambdaQueryWrapper相当于mp的LambdaQueryWrapper 两者可以无缝切换 MPJQueryWrapper.lambda() ===> MPJLambdaQueryWrapper MPJLambdaQueryWrapper.stringQuery() ===> MPJQueryWrapper ## MPJJoinLambdaQueryWrapper用法 #### MPJJoinLambdaQueryWrapper示例 #### 简单的3表查询 ```java class test { @Resource private UserMapper userMapper; void testJoin() { List list = userMapper.selectJoinList(UserDTO.class, new MPJJoinLambdaQueryWrapper() .selectAll(UserDO.class) .select(UserAddressDO::getTel) .selectAs(UserAddressDO::getAddress, UserDTO::getUserAddress) .select(AreaDO::getProvince, AreaDO::getCity) .leftJoin(UserAddressDO.class, UserAddressDO::getUserId, UserDO::getId) .leftJoin(AreaDO.class, AreaDO::getId, UserAddressDO::getAreaId) .eq(true, UserDO::getId, 1) .like(true, UserAddressDO::getTel, "1") .gt(true, UserDO::getId, 5)); } } ``` 对应sql ``` SELECT t.id, t.name, t.sex, t.head_img, t1.tel, t1.address AS userAddress, t2.province, t2.city FROM user t LEFT JOIN user_address t1 ON t1.user_id = t.id LEFT JOIN area t2 ON t2.id = t1.area_id WHERE ( t.id = ? AND t1.tel LIKE ? AND t.id > ?) ``` 说明: * UserDTO.class 查询结果返回类(resultType) * selectAll() 查询指定实体类的全部字段 * select() 查询指定的字段,支持可变参数,同一个select只能查询相同表的字段 故将UserAddressDO和AreaDO分开为两个select() * selectAs() 字段别名查询,用于数据库字段与业务实体类属性名不一致时使用 * leftJoin() 参数说明 第一个参数: 参与连表的实体类class 第二个参数: 连表的ON字段,这个属性必须是第一个参数实体类的属性 第三个参数: 参与连表的ON的另一个实体类属性 * 默认主表别名是t,其他的表别名以先后调用的顺序使用t1,t2,t3.... * 条件查询,可以查询主表以及参与连接的所有表的字段,全部调用mp原生的方法,正常使用没有sql注入风险 #### 分页查询 ```java class test { @Resource private UserMapper userMapper; void testJoin() { IPage iPage = userMapper.selectJoinPage(new Page<>(2, 10), UserDTO.class, new MPJJoinLambdaQueryWrapper() .selectAll(UserDO.class) .select(UserAddressDO::getTel) .selectAs(UserAddressDO::getAddress, UserDTO::getUserAddress) .select(AreaDO::getProvince, AreaDO::getCity) .leftJoin(UserAddressDO.class, UserAddressDO::getUserId, UserDO::getId) .leftJoin(AreaDO.class, AreaDO::getId, UserAddressDO::getAreaId)); } } ``` 对应sql ``` SELECT t.id, t.name, t.sex, t.head_img, t1.tel, t1.address AS userAddress, t2.province, t2.city FROM user t LEFT JOIN user_address t1 ON t1.user_id = t.id LEFT JOIN area t2 ON t2.id = t1.area_id LIMIT ?,? ``` ## MPJQueryWrapper和MPJLambdaQueryWrapper ### 简单的3表查询 ```java class test { @Resource private UserMapper userMapper; void testJoin() { List list = userMapper.selectJoinList(UserDTO.class, new MPJLambdaQueryWrapper() .selectAll(UserDO.class) .select("addr.tel", "addr.address", "a.province") .leftJoin("user_address addr on t.id = addr.user_id") .rightJoin("area a on addr.area_id = a.id") .gt(true, UserDO::getId, 1) .eq(true, UserDO::getSex, "男") .stringQuery() .like(true, "addr.tel", "1") .le(true, "a.province", "1")); } } ``` 对应sql ``` SELECT t.id, t.name, t.sex, t.head_img, addr.tel, addr.address, a.province FROM user t LEFT JOIN user_address addr on t.id = addr.user_id RIGHT JOIN area a on addr.area_id = a.id WHERE ( t.id > ? AND t.sex = ? AND addr.tel LIKE ? AND a.province <= ?) ``` 说明: * UserDTO.class 查询结果类(resultType) * selectAll(UserDO.class) 查询主表全部字段(主表实体类) * select() mp的select策略是覆盖,以最后一次为准,这里的策略是追加,可以一直select 主表字段可以用lambda,会自动添加表别名,主表别名默认是 t ,非主表字段必须带别名查询 * leftJoin() rightJoin() innerJoin() 传sql片段 格式 (表 + 别名 + 关联条件) * stringQuery() lambda查询转string查询 * lambda() string查询转lambda查询 * 条件查询,可以查询主表以及参与连接的所有表的字段,全部调用mp原生的方法,正常使用没有sql注入风险 ### 分页查询 ```java class test { @Resource private UserMapper userMapper; void testJoin() { IPage page = userMapper.selectJoinPage(new Page<>(1, 10), UserDTO.class, new MPJLambdaQueryWrapper() .selectAll(UserDO.class) .select("addr.tel", "addr.address") .select("a.province") .leftJoin("user_address addr on t.id = addr.user_id") .rightJoin("area a on addr.area_id = a.id")); } } ``` 对应sql ``` SELECT t.id, t.name, t.sex, t.head_img, addr.tel, addr.address, a.province FROM user t LEFT JOIN user_address addr on t.id = addr.user_id RIGHT JOIN area a on addr.area_id = a.id LIMIT ?,? ``` ### 还可以这么操作,但不建议 ```java class test { @Resource private UserMapper userMapper; void testJoin() { List list = userMapper.selectJoinList(UserDTO.class, new MPJLambdaQueryWrapper() .selectAll(UserDO.class) .select("addr.tel", "addr.address") //行列转换 .select("CASE t.sex WHEN '男' THEN '1' ELSE '0' END AS sex") //求和函数 .select("sum(a.province) AS province") //自定义数据集 .leftJoin("(select * from user_address) addr on t.id = addr.user_id") .rightJoin("area a on addr.area_id = a.id") .eq(true, UserDO::getId, 1) .stringQuery() .like(true, "addr.tel", "1") .le(true, "a.province", "1") .orderByDesc("addr.id")); } } ``` 对应sql ``` SELECT t.id, t.name, t.sex, t.head_img, addr.tel, addr.address, CASE t.sex WHEN '男' THEN '1' ELSE '0' END AS sex, sum(a.province) AS province FROM user t LEFT JOIN (select * from user_address) addr on t.id = addr.user_id RIGHT JOIN area a on addr.area_id = a.id WHERE ( t.id = ? AND addr.tel LIKE ? AND a.province <= ?) ORDER BY addr.id DESC ``` # [wiki](https://gitee.com/best_handsome/mybatis-plus-join/wikis)