@MapKey----mybatis返回Map

Posted 2022-11-12 戚焱

mybatis返回Map

有时候我们可能想让一条查询语句直接能够返回Map，而不是List。

可以使用@MapKey来指定实体类中让哪个属性来当key(注意是实体类中的属性，不是表中的字段)，而value就是所需的对象。

实体类：People，该实体类不一定是与数据库表对应的

@Data
@TableName("people")
public class People implements Serializable 

    private static final long serialVersionUID = 1L;

    @TableId("id")
    private Integer id;

    @TableField("name")
    private String name;

    @TableField("address")
    private String address;

    @TableField("phone")
    private Long phone;

mapper里：

public interface PeopleMapper extends BaseMapper<People> 

    //这个name是People中的属性，而不是表中的字段
    @MapKey("name")
    Map<String,People> getAllPeople();

xml中:

   <select id="getAllPeople" resultType="java.util.Map" resultMap="peopleResultMap">
        select id, `name`, address, phone
        from people
    </select>

    <resultMap id="peopleResultMap" type="com.springlearn.qiyan.mapkey.entity.People">
        <result property="name" column="name"/>
        <result property="phone" column="phone"/>
        <result property="address" column="address"/>
    </resultMap>

在xml中应该写好该类对应的resultMap

表中数据

返回值：

    "code": 200,
    "msg": "处理成功",
    "data": 
        "陆游": 
            "id": 4,
            "name": "陆游",
            "address": "北京",
            "phone": 13954687412
        ,
        "辛弃疾": 
            "id": 3,
            "name": "辛弃疾",
            "address": "济南",
            "phone": 12574693258
        ,
        "李白": 
            "id": 1,
            "name": "李白",
            "address": "成都",
            "phone": 13469521374
        ,
        "韩信": 
            "id": 2,
            "name": "韩信",
            "address": "山东",
            "phone": 19634895213
        ,
        "苏轼": 
            "id": 5,
            "name": "苏轼",
            "address": "苏州",
            "phone": 13697532169