mybatis查询返回一个对象中带有集合

星辰sea

发布于 2022-10-29 09:31:09

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发布于 2022-10-29 09:31:09

文章被收录于专栏：星辰SEA星辰SEA

1.首先创建两个测试类

@Data
@TableName("z_test_grade")
public class ZTestGradeEntity implements Serializable {

    private Integer id;

    private String name;

    private String address;
}

@Data
@TableName("z_test_teacher")
public class ZTestTeacherEntity implements Serializable {
    @TableId(type = IdType.AUTO)
    private Integer id;

    private String name;

    private Integer age;

    private String categroy;

    private String level;

    private Integer gradeldId; //关联主表id
}

2.创建返回类Dto 用来接收查询出来的结果

@Data
public class ResultDto {
    private Integer id;

    private String name;

    private String address;

    private List<ZTestTeacherEntity> teacherList;
}

3.重点：然后配置xml

//<-- 关联集合就是用collection-->
<resultMap id="gradeMap" type="com.personal.modules.test.ResultDto">
        <id column="id" property="id" />
        <result column="name" property="name"/>
        <result column="address" property="address"/>
        <collection property="teacherList" ofType="com.personal.modules.test.ZTestTeacherEntity">
            <id property="id" column="t_id" />
            <result column="t_name" property="name"/>
            <result column="t_age" property="age"/>
            <result column="t_categroy" property="categroy"/>
            <result column="t_level" property="level"/>
            <result column="t_gradeldId" property="gradeldId"/>
        </collection>
    </resultMap>

常用的属性就不说了，特别要注意的是ofType这个要指向各自表的实体类，然后子表的column属性不要和主表重名，一旦重名就会出问题，不知道是不是我配置的问题，希望有大佬指教，反正不重名就可以接下来就是查询语句了，很简单，只要别名和上面resultMap对的上就ok

4.SQL

//SQL:
<select id="test" resultMap="gradeMap">
        SELECT
               ztg.id,
               ztg.name,
               ztg.address,
               ztt.id as t_id,
               ztt.name as t_name,
               ztt.age as t_age,
               ztt.categroy as t_categroy,
               ztt.level as t_level,
               ztt.gradeld_id as t_gradeldId
        FROM
            z_test_grade ztg
                LEFT JOIN z_test_teacher ztt ON ztt.gradeld_id = ztg.id

    </select>

5.返回结果数据

{
    "code":200,
    "data":[
        {
            "id":1,
            "name":"3年一班",
            "address":"1楼",
            "teacherList":[
                {
                    "id":1,
                    "name":"宋元桥",
                    "age":50,
                    "categroy":"武当",
                    "level":"1",
                    "gradeldId":1
                },
                {
                    "id":2,
                    "name":"俞莲舟",
                    "age":43,
                    "categroy":"武当",
                    "level":"1",
                    "gradeldId":1
                }
            ]
        },
        {
            "id":2,
            "name":"3年二班",
            "address":"2楼",
            "teacherList":[
                {
                    "id":3,
                    "name":"张三",
                    "age":55,
                    "categroy":"武当",
                    "level":"1",
                    "gradeldId":2
                }
            ]
        }
    ]
}

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原始发表：2021-12-13 ，如有侵权请联系 cloudcommunity@tencent.com 删除

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