mybatis中resultMap结果返回类型

当查询结果属性名（字段）和模型类中不一样时，其查询结果如果用resultType接受，字段不一样的属性值就会丢失，而resultMap可以解决这个问题。
property表示的实体类中属名
colum表示sql语句查询字段名（如果查询字段没有起别名，即是数据库字段名）
在这里插入图片描述

public interface UserMapper {
    //返回为resultMap类型的使用
    public User findUserByResultMap(int userId);
}

xml配置：

<?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.gyf.mapper.UserMapper">
  
    <resultMap id="userResultMap" type="user">
        <id property="id" column="id_"></id>
        <result property="username" column="username_"></result>
        <result property="sex" column="sex_"></result>
        <result property="birthday" column="birthday_"></result>
        <result property="address" column="address_"></result>
    </resultMap>
    
    <select id="findUserByResultMap" parameterType="int" resultMap="userResultMap">
        select id id_,
        username username_,
        sex sex_,
        birthday birthday_,
        address address_
        from user where id = #{id}
    </select>
</mapper>

测试类：

public class Demo01 {
    SqlSession session;
    @Before
    public void before() throws IOException {
        System.out.println("before....获取session");
        //读取配置文件
        InputStream is = Resources.getResourceAsStream("SqlMapConfig.xml");
        //通过SqlSessionFactoryBuilder创建SqlSessionFactory会话工厂
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);
        //通过SqlSessionFactory创建SqlSession
        session = sessionFactory.openSession();
    }

    @After
    public void after(){
        session.close();
    }


    /*
        结果类型resultMap
     */
    @Test
    public void test2() throws IOException {
        UserMapper userMapper = session.getMapper(UserMapper.class);
        //通过模型的包装类来查询用户
        User user  = userMapper.findUserByResultMap(1);
        System.out.println(user);
    }
}

mybatis中resultMap结果返回类型

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