Mybatis的mapper返回map结果集(超详细讲解）[通俗易懂]

/** * @author : xjszsd * @date : 2021-12-13 16:20 */
public interface IAccountDao { 
   
    //返回一条记录的map；key就是列名，值就是对应的值
    Map<String,Object> selectAll(Integer id);

    /** * 此处若将map的key的类型改为其他类型，不影响@MapKey给map的key赋值 * @return */
    @MapKey("name")//指定数据库中id字段作为map的key
    Map<String,Map<String,Object>> select();
}

<!-- Map<String,Object> selectAll(Integer id); -->
    <select id="selectAll" parameterType="Integer" resultType="java.util.Map">
        select id , money from account where id=#{id}
    </select>

<!-- Map<String,Map<String,Object>> select(); -->
    <select id="select" resultType="java.util.Map">
        select id,name,money from account
    </select>

@Before
public void init() throws IOException { 

//1.读取配置文件
in = Resources.getResourceAsStream("SqlMapConfig.xml");
//2.创建SqlSessionFactory工厂
SqlSessionFactoryBuilder builder=new SqlSessionFactoryBuilder();
factory=builder.build(in);
//3.使用工厂生产SqlSession对象
session= factory.openSession();
}
@After
public void after() throws IOException { 

session.close();
in.close();
}   

 @Test
public void selectTest(){ 

IAccountDao mapper = session.getMapper(IAccountDao.class);
Map<String, Object> map = mapper.selectAll(1);
System.out.println(map);
}

 @Test
public void selectTest2(){ 

IAccountDao mapper = session.getMapper(IAccountDao.class);
Map<String, Map<String, Object>> map = mapper.select();
System.out.println(map);
}