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2025-07-11 00:02:22 +08:00 · 2021-11-17 12:16:35 +08:00 · 2021-11-17 12:16:35 +08:00 · a972e825ee
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+# mybatis-plus-join
+
+* 本页功能只能在1.2.0测试版中使用,最新版本 1.2.0.Beta5
+
+* 点个Star支持一下吧 :)
+
+QQ群:1022221898
+
+## 使用方法
+
+### 安装
+
+- Maven
+  ```xml
+  <dependency>
+      <groupId>com.github.yulichang</groupId>
+      <artifactId>mybatis-plus-join</artifactId>
+      <version>1.2.0.Beta5</version>
+  </dependency>
+  ```
+- Gradle
+  ```
+   implementation group: 'com.github.yulichang', name: 'mybatis-plus-join', version: '1.2.0.Beta5'
+  ```
+  或者clone代码到本地执行 mvn install, 再引入以上依赖  
+  <br>
+  注意: mybatis plus version >= 3.4.0
+  <br>
+
+### 使用
+
+* mapper继承MPJBaseMapper
+* service继承MPJBaseService (可选)
+* serviceImpl继承MPJBaseServiceImpl (可选)
+
+#### @EntityMapping 和 @FieldMapping 注解
+
+UserDO.java
+
+```java
+
+@Data
+@TableName("user")
+public class UserDO {
+
+    @TableId
+    private Integer id;
+    private Integer pid;//父id
+    /* 其他属性略 */
+
+    /**
+     * 查询上级 一对一
+     */
+    @TableField(exist = false)
+    @EntityMapping(thisField = "pid", joinField = "id")
+    private UserDO pUser;
+
+    /**
+     * 查询下级 一对多
+     */
+    @TableField(exist = false)
+    @EntityMapping(thisField = "id", joinField = "pid")
+    private List<UserDO> childUser;
+
+    /**
+     * 查询地址 (一对多)
+     */
+    @TableField(exist = false)
+    @EntityMapping(thisField = "id", joinField = "userId")
+    private List<UserAddressDO> addressList;
+
+    /**
+     * 绑定字段 （一对多）
+     */
+    @TableField(exist = false)
+    @FieldMapping(tag = UserDO.class, thisField = "id", joinField = "pid", select = "id")
+    private List<Integer> childIds;
+}
+```
+
+使用
+
+```java
+/**
+ * 一对一，一对多关系映射查询
+ * 映射只对以Deep结尾有效，比如 getByIdDeep listByIdsDeep 等
+ * 如果不需要关系映射就使用mybatis plus原生方法即可，比如 getById listByIds 等
+ *
+ * 注意：关系映射不会去关联查询，而是执行多次单表查询（对结果汇总后使用in语句查询,再对结果进行匹配）
+ */
+@SpringBootTest
+class MappingTest {
+    @Resource
+    private UserMapper userMapper;
+
+    @Test
+    void test1() {
+        UserDO deep = userMapper.selectByIdDeep(2);
+        System.out.println(deep);
+    }
+
+    @Test
+    void test2() {
+        List<UserDO> list = userMapper.selectListDeep(Wrappers.emptyWrapper());
+        list.forEach(System.out::println);
+    }
+
+    @Test
+    void test3() {
+        Page<UserDO> page = userMapper.selectPageDeep(new Page<>(2, 2), Wrappers.emptyWrapper());
+        page.getRecords().forEach(System.out::println);
+    }
+
+    /**
+     * 更多方法请查阅 MPJDeepMapper 或者 MPJDeepService
+     * 使用方式与 mybatis plus 一致
+     */
+}
+```
+
+MPJMapping 说明：
+
+* @EntityMapping / @FieldMapping tag 关联实体类
+* @EntityMapping / @FieldMapping thisField 当前类关联对应的字段的属性名，可以不填，默认为当前类的主键
+* @EntityMapping / @FieldMapping joinField 关联类对应的字段的属性名，可以不填，默认为关联类的主键
+* @EntityMapping / @FieldMapping isThrowExp 一对一查询时,如果查询到多条记录是否抛出异常,true:抛出异常,false:获取列表第一条数据
+*
+
+更多功能请看代码注释 [EntityMapping](https://gitee.com/best_handsome/mybatis-plus-join/blob/master/src/main/java/com/github/yulichang/annotation/EntityMapping.java)
+[FieldMapping](https://gitee.com/best_handsome/mybatis-plus-join/blob/master/src/main/java/com/github/yulichang/annotation/FieldMapping.java)
+
+
+
+