mybatis一对多

情景：一个用户有多个账户
需求：查询账户及其关联的用户信息
实现：
1、自己另外封装个实体类（不常用）
2、使用resultMap 和 association

<?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="com.example.lernamybatis.repository.IAccountDAO">

  <resultMap id="accountUserMap" type="com.example.lernamybatis.entity.Account">
    <id property="id" column="aid"></id>
    <result property="uid" column="uid"></result>
    <result property="money" column="money"></result>
    <association property="user" column="uid">
      <id property="id" column="id"></id>
      <result column="username" property="userName"></result>
      <result column="address" property="address"></result>
      <result column="sex" property="sex"></result>
      <result column="birthday" property="birthday"></result>
    </association>
  </resultMap>

  <select id="findAll" resultMap="accountUserMap">
        select u.*,a.id as aid,a.uid,a.money from account a ,user u where u.id = a.uid
  </select>

  <select id="findAllAccount" resultType="com.example.lernamybatis.entity.AccountUser">
    select a.*, u.username,u.address from account a, user u where a.uid=u.id;
  </select>
</mapper>

需求：查询所有用户及其拥有的账户
实现：使用collection标签，对应列名和实体字段名

 <resultMap id="userAccountMap" type="com.example.lernamybatis.entity.User">
    <id property="id" column="id"></id>
    <result property="userName" column="username"></result>
    <result property="sex" column="sex"></result>
    <result property="address" column="address"></result>
    <result property="birthday" column="birthday"></result>
    <collection property="accounts" ofType="com.example.lernamybatis.entity.Account">
      <id property="id" column="aid"></id>
      <result property="uid" column="uid"></result>
      <result property="money" column="money"></result>
    </collection>
  </resultMap>

  <select id="selectAll" resultMap="userAccountMap">
        select u.*, a.id as aid, a.uid, a.money from user u left join account a on u.id = a.uid
  </select>