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114 lines
3.4 KiB
Markdown
114 lines
3.4 KiB
Markdown
# mybatis-plus-join
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#### @EntityMapping 和 @FieldMapping 注解
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UserDO.java
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```java
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@Data
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@TableName("user")
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public class UserDO {
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@TableId
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private Integer id;
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private Integer pid;//父id
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/* 其他属性略 */
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/**
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* 查询上级 一对一
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*/
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@TableField(exist = false)
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@EntityMapping(thisField = "pid", joinField = "id")
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private UserDO pUser;
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/**
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* 查询下级 一对多
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*/
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@TableField(exist = false)
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@EntityMapping(thisField = "id", joinField = "pid")
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private List<UserDO> childUser;
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/**
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* 带条件的查询下级 一对多
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*/
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@TableField(exist = false)
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@EntityMapping(thisField = "id", joinField = "pid",
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condition = {
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@MPJMappingCondition(column = "sex", value = "0"),//sex = '0' 默认条件是等于
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@MPJMappingCondition(column = "name", value = "张三", keyWord = SqlKeyword.LIKE)//name like '%a%'
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},
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apply = @MPJMappingApply(value = "id between 1 and 20"))//拼接sql 同 wrapper.apply()
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private List<UserDO> childUserCondition;
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/**
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* 查询地址 (一对多)
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*/
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@TableField(exist = false)
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@EntityMapping(thisField = "id", joinField = "userId")
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private List<UserAddressDO> addressList;
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/**
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* 绑定字段 （一对多）
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*/
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@TableField(exist = false)
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@FieldMapping(tag = UserDO.class, thisField = "id", joinField = "pid", select = "id")
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private List<Integer> childIds;
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}
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```
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使用
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```java
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/**
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* 一对一，一对多关系映射查询
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* 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
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* <p>
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* 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）
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*/
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@SpringBootTest
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class MappingTest {
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@Resource
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private UserMapper userMapper;
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@Test
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void test1() {
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UserDO deep = userMapper.selectByIdDeep(2);
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System.out.println(deep);
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}
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@Test
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void test2() {
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List<UserDO> list = userMapper.selectRelation(mapper -> mapper.selectList(Wrappers.emptyWrapper()));
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list.forEach(System.out::println);
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}
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@Test
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void test3() {
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Page<UserDO> page = new Page<>(2, 2);
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Page<UserDO> result = userMapper.selectRelation(mapper -> mapper.selectPage(page, Wrappers.emptyWrapper()));
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result.getRecords().forEach(System.out::println);
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}
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/*
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更多方法请查阅 MPJDeepMapper 或者 MPJDeepService
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使用方式与 mybatis plus 一致
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*/
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}
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```
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MPJMapping 说明：
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* @EntityMapping / @FieldMapping tag 关联实体类
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* @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
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* @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
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* @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
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*
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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)
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[FieldMapping](https://gitee.com/best_handsome/mybatis-plus-join/blob/master/src/main/java/com/github/yulichang/annotation/FieldMapping.java)
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