一对一一对多关系映射注解实现

2025-07-11 00:02:22 +08:00 · 2021-08-12 14:04:14 +08:00 · 2021-08-12 14:04:14 +08:00 · 4121413a7f
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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.Beta1
+
+* 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.Beta1</version>
+  </dependency>
+  ```
+- Gradle
+  ```
+   implementation group: 'com.github.yulichang', name: 'mybatis-plus-join', version: '1.2.0.Beta1'
+  ```
+  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 (必选)
+* service继承MPJBaseService (可选)
+* serviceImpl继承MPJBaseServiceImpl (可选)
+
+#### @MPJMapping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 */
+
+    /**
+     *  一对一
+     */
+    @TableField(exist = false)
+    @MPJMapping(tag = UserDO.class, thisField = "pid")
+    private UserDO pUser;
+
+    /**
+     *  一对多
+     */
+    @TableField(exist = false)
+    @MPJMapping(tag = UserAddressDO.class, joinField = "userId")
+    private List<UserAddressDO> addressDOList;
+}
+```
+
+UserAddressDO.java
+
+```java
+
+@Data
+@TableName("user_address")
+public class UserAddressDO {
+
+    @TableId
+    private Integer id;
+    private Integer userId;
+    /* 其他属性略 */
+}
+```
+
+使用
+
+```java
+
+@SpringBootTest
+public class MPJDeepTest {
+    @Resource
+    private UserService userService;
+
+    @Test
+    void test1() {
+        UserDO deep = userService.getByIdDeep(1);
+        System.out.println(deep);
+    }
+
+    @Test
+    void test2() {
+        List<UserDO> list = userService.listByIdsDeep(Arrays.asList(1, 4));
+        list.forEach(System.out::println);
+    }
+
+    @Test
+    void test3() {
+        List<UserDO> list = userService.listByMapDeep(new HashMap<String, Object>() {{
+            put("id", 1);
+        }});
+        list.forEach(System.out::println);
+    }
+
+    @Test
+    void test4() {
+        UserDO one = userService.getOneDeep(Wrappers.<UserDO>lambdaQuery()
+                .eq(UserDO::getId, 1));
+        System.out.println(one);
+    }
+
+    @Test
+    void test5() {
+        Map<String, Object> deep = userService.getMapDeep(Wrappers.<UserDO>lambdaQuery()
+                .eq(UserDO::getId, 1));
+        System.out.println(deep);
+    }
+}
+```
+
+MPJMapping 说明：
+
+* MPJMapping tag 关联实体类
+* MPJMapping 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
+* MPJMapping 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
+* MPJMapping 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 [MPJMapping](https://gitee.com/best_handsome/mybatis-plus-join/blob/master/src/main/java/com/github/yulichang/annotation/MPJMapping.java)
+
+
+
+