【Mybatis】Mybatis一對多、多對一

Mybatis多對一【association】

1. 多對一

private GradeVo gradeVo;

<select id="get" resultType="com.hxh.basic.project.vo.GradeVo" parameterType="int">
select * from grade where id = #{id};
</select>

<resultMap id="TestMybatis" type="com.demo.pojo.Student" autoMapping="true">
<id property="stuNo" column="stuNo"></id>
<association property="grade" javaType="com.demo.pojo.Grade" column="gradeId"
 select="com.demo.dao.GradeDao.get"></association>
</resultMap>

<select id="getAll" resultMap="TestMybatis">
select * from student
</select>

{
   "code": 0,
   "message":"ok",
   "data": [
        {
           "id": 6,
           "nickname":"Consumer",
           "username":"於瑤",
           "birthday":"2021-03-03T00:00:00",
           "gradeVo": {
               "id": 1,
               "gradeNane":"一年級"
            }
        },
        {
           "id": 7,
           "nickname":"Company",
           "username":"白志超",
           "birthday":"2021-03-05T00:00:00",
           "gradeVo": {
               "id": 0,
               "gradeNane":"幼兒園"
            }
        }
    ]
}

Mybatis一對多【collection】

1. 一對多

private GradeVo gradeVo;

<select id="get" resultType="com.hxh.basic.project.vo.UserVo" parameterType="int">
select * from user where status = #{status};
</select>

<resultMap id="resultMap" type="com.hxh.basic.project.vo.GradeVo" autoMapping="true">
<id property="id" column="id"></id>
<collection property="list" ofType="com.hxh.basic.project.vo.UserVo" javaType="java.util.List" column="id"
select="com.hxh.basic.project.mapper.UserMapper.get"></collection>
</resultMap>

<select id="getAll" resultMap="resultMap">
select * from grade;
</select>

{
   "code": 0,
   "message":"ok",
   "data": [
        {
           "id": 0,
           "gradeNane":"幼兒園",
           "list": [
                {
                   "id": 5,
                   "nickname":"Producer",
                   "username":"高佳琪",
                   "birthday":"2021-03-03T00:00:00"
                }
            ]
        },
        {
           "id": 1,
           "gradeNane":"一年級",
           "list": [
                {
                   "id": 4,
                   "nickname":"LouisVan",
                   "username":"王瑩",
                   "birthday":"2021-03-03T00:00:00"
                }
            ]
        },
        {
           "id": 2,
           "gradeNane":"二年級",
           "list": []
        }
    ]
}