MyBatis高级查询 一对多映射

数据库表在一对一映射中。

在数据库sys_user_role中新增一条记录

一个用户可以有多个角色。查询出所有用户和所对应的角色。

1.collection集合的嵌套结果映射

<!-- SysUserMapper.xml -->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="test.dao.SysUserMapper">
  <resultMap id="BaseResultMap" type="test.model.SysUser">
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
    -->
    <id column="id" jdbcType="BIGINT" property="id" />
    <result column="user_password" jdbcType="VARCHAR" property="userPassword" />
    
    <result column="user_name" jdbcType="VARCHAR" property="userName" />
    <result column="user_email" jdbcType="VARCHAR" property="userEmail" />
    <result column="create_time" jdbcType="TIMESTAMP" property="createTime" />
    <result column="user_info" jdbcType="LONGVARCHAR" property="userInfo" />
    <result column="head_img" jdbcType="LONGVARBINARY" property="headImg" />
    
  </resultMap>
  
  <!-- 继承上面的UserResultMap -->
  <resultMap type="test.model.SysUser" id="userRoleResultMap" extends="BaseResultMap">
      <!-- roleList相关属性 -->
    <collection property="roleList" resultMap="test.dao.SysRoleMapper.BaseResultMap" columnPrefix="role_">
    </collection>
  </resultMap>
  
  <select id="selectUserRoleListAll" resultMap="userRoleResultMap">
      select 
          u.id,
          u.user_name,
          u.user_password,
          u.user_email,
        u.create_time,
          u.user_info,
          u.head_img,
          r.id role_id,
          r.role_name role_role_name,
          r.enabled role_enabled,
          r.create_by role_create_by,
          r.create_time role_create_time
          from sys_user u 
          inner join sys_user_role ur on u.id=ur.user_id
          inner join sys_role r on ur.role_id=r.id
  </select>
</mapper>