多对多查询，mybatis使用collection接收集合类型数据

entity

@Data
public class TestEntity {
    private Long id;
    private String name;
    private List<Test2Entity> aihao;
}

@Data
public class Test2Entity {
    private Long id;
    private String aihao;
}
1
2
3
4
5
6
7
8
9
10
11
12

mapper

注意，如果表主键相同，那么采用as取别名方式定义字段

<mapper namespace="com.io.mapper.TestMapper">
    <resultMap id="umap" type="com.io.entity.TestEntity">
            <id column="tid" property="id"/>
            <result column="name" property="name"/>
            <collection property="aihao" javaType="java.util.List" ofType="com.io.entity.Test2Entity">
            	//列名也应该按照别名来写
                <id column="ttid" property="id"/>
                <result column="aihao" property="aihao"/>
            </collection>
    </resultMap>
    <select id="query" resultMap="umap">
        SELECT
        // 字段 as 别名
            t1.*,t1.id as tid,t2.*,t2.id as ttid
        FROM
            test1 t1
                LEFT JOIN t1_t2 t12 ON t12.t1id=t1.id
                LEFT JOIN test2 t2 on t2.id=t12.t2id
    </select>
</mapper>
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20