A表有某个字段与B表关联，且和B表多个数据有关系。如现在展示全部学生，每个学生有语数成绩。现在B表的数据存在列表里。

A 实体类

public class Student{

privite Long id;
privite String name;
privite String sex;

//用列表存放成绩
privite List<Score> personalScore;
}

B 实体类

public class Score{

privite Long id;
privite Integer chinese;
privite Integer maths;
}

StudentMapper

<?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.test.mapper.StudentMapper">

<resultMap id="baseResultMap" type="com.test.entity.Student">
<id column="id" property="id"/>
<id column="name" property="name"/>
<id column="sex" property="sex"/>
</resultMap>

// 如果只查学生表，则resultMap="baseResultMap"
<select id = getAllList resultMap = "fullMap">
	select a.*,
		b.chinese as i_chinese,
		b.maths as i_maths
	from student a
	left join score b on a.id = b.id
</select>

//定义fullMap
<resultMap id="fullMap" type="com.test.entity.Student" extends="baseResultMap">
        <collection property="personalScore" columnPrefix="i_"
                    resultMap="com.test.mapper.ScoreMapper.baseResultMap">
        </collection>
    </resultMap>