Mybatis多对一【association】
- 多对一
/**
* 添加部门实体字段
* 第一步：多方添加一方的实体类：com/hxh/basic/project/vo/UserVo.java:18
*/
private GradeVo gradeVo;
/*第二步：在一方Mapper中添加根据编号检索*/
<select id="get" resultType="com.hxh.basic.project.vo.GradeVo" parameterType="int">
select * from grade where id = #{id};
</select>
/*第三步：在多方Mapper中进行resultMap映射查询*/
<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>
/**
* 第四步：调用Controller查询结果
* 请求路径：http://localhost:8080/basic_project/user/getAll
*/
{
"code": 0,
"message": "ok",
"data": [
{
"id": 6,
"nickname": "Consumer",
"username": "于瑶",
"birthday": "2021-03-03T00:00:00",
"gradeVo": {
"id": 1,
"gradeNane": "一年级"
}
},
{
"id": 7,
"nickname": "Company",
"username": "白志超",
"birthday": "2021-03-05T00:00:00",
"gradeVo": {
"id": 0,
"gradeNane": "幼儿园"
}
}
]
}
Mybatis一对多【collection】
- 一对多
/**
* 添加用户字段集合
* 第一步：多方实体类添加用户集合：com/hxh/basic/project/vo/GradeVo.java:27
*/
private List<UserVo> list;
/*第二步：在多方Mapper中添加根据状态检索*/
<select id="get" resultType="com.hxh.basic.project.vo.UserVo" parameterType="int">
select * from user where status = #{status};
</select>
/*第三步：在一方Mapper中进行resultMap映射查询*/
<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>
/**
* 第四步：调用Controller查询结果
* 请求路径：http://localhost:8080/basic_project/grade/getAll
*/
{
"code": 0,
"message": "ok",
"data": [
{
"id": 0,
"gradeNane": "幼儿园",
"list": [
{
"id": 5,
"nickname": "Producer",
"username": "高佳琪",
"birthday": "2021-03-03T00:00:00"
}
]
},
{
"id": 1,
"gradeNane": "一年级",
"list": [
{
"id": 4,
"nickname": "LouisVan",
"username": "王莹",
"birthday": "2021-03-03T00:00:00"
}
]
},
{
"id": 2,
"gradeNane": "二年级",
"list": []
}
]
}
概念
- 一对多和多对一
- 一对多：collection【多方添加一方的实体类、property：实体类变量名称、JavaType：实体类的返回值类型、column：当前的外键，如status、select：调用一方的ID查询】
- 多对一：association【一方添加多方集合、property：多方的变量名称、ofType：集合中多方的返回值类型、javaType：List包路径、column：当前ID，select：调用多方的根据外键查询】
