1.单表查询时，ResultMap的使用方法
studentMapper.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="com.bb.mapper.StudentMapper">
    <!--使用resultMap-->
    <select id="selectWithResultMap" resultMap="studentResultMap">
        select * from student
    </select>
<!--    id对应select标签的resultMap值，type为sql语句的返回值类型-->
    <resultMap id="studentResultMap" type="Student">
        <id property="id" column="id"></id>
        <result property="name" column="name"></result>
        <result property="age" column="age"></result>
    </resultMap>
</mapper>

StudentMapper.java

package com.bb.mapper;
import com.bb.entity.Student;
import org.apache.ibatis.annotations.Select;
import java.util.HashMap;
public interface StudentMapper {
    /*
     * 1。方法名和StudentMapper.xml文件中标签的id值一致
     * 2。方法输入参数与StudentMapper.xml文件中标签的parameterType一致
     * 3。返回值与StudentMapper.xml文件中标签的resultType一致
     *
     */
    Student selectStudent(int id);
    Student selectStudentByParams(Student student);
    Student selectStudentByParams2(HashMap map);
    //返回值为resultMap中的type的值
    Student selectWithResultMap();
}

TestMybatis.java

package com.bb.service;

import com.bb.entity.Student;
import com.bb.mapper.StudentMapper;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;
import java.io.Reader;
import java.util.HashMap;

public class TestMybatis {
    //使用ResultMap接收sql返回值
    public static void queryWithResultMap() throws IOException {
        Reader resourceAsReader = Resources.getResourceAsReader("conf.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsReader);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
        Student student = mapper.selectWithResultMap();
        System.out.println("使用ResultMap接收sql返回值：");
        System.out.println(student.getId()+"-"+student.getName()+"-"+student.getAge());
    }
    public static void main(String[] args) throws IOException {
       queryWithResultMap();
    }
}

2.多表联合查询时，ResultMap的使用方法
见第十章 一对一联合查询的第二种方法
2.使用ResultMap实现