查询

DO

List<DO>

Map<String,DO>

• @MapKey指定Map的Key
• Key必须是 SQL 查出来的字段

@MapKey("id")
Map<Long, User> selectUserMap();

<select id="selectUserMap" resultType="com.example.User">
    SELECT id, name, age FROM user
</select>

{
  1: User{id=1, name=张三},
  2: User{id=2, name=李四}
}

List<Map<String,Object>>

List<Map<String, Object>> selectListMap();

<select id="selectListMap" resultType="map">
    SELECT id, name, age
    FROM user
</select>

[
  {id=1, name=张三, age=18},
  {id=2, name=李四, age=20}
]

Map 的 key默认是 数据库字段名（或别名）

SELECT id AS userId, name AS userName FROM user

{userId=1, userName=张三}