Mybatis之ResultMap

public class User implements Serializable {
    private static final long serialVersionUID = 6716332190979093860L;
    private Integer id;
    private String username;
    private String password;
    private Integer age;
​
    
    public Integer getAge() {
        return age;
    }
​
    public void setAge(Integer age) {
        this.age = age;
    }
​
    public Integer getId() {
        return id;
    }
​
    public void setId(Integer id) {
        this.id = id;
    }
​
    public String getUsername() {
        return username;
    }
​
    public void setUsername(String username) {
        this.username = username;
    }
​
    public String getPassword() {
        return password;
    }
​
    public void setPassword(String password) {
        this.password = password;
    }
    
    
    @Override
    public String toString() {
        return "User [id=" + id + ", username=" + username + ", password="
                + password + ", age=" + age + "]";
    }
    
}

create table user(id int primary key auto_increment,username varchar(20),age int ,password varchar(20));

 <!-- 
    User findUserById(Integer id);
    resultType: 指定返回的结果类型
  -->
  <select id="findUserById" resultType="cn.tedu.spring.entity.User">
    select username,password,age,id from user where id=#{id}
  </select>

 <!-- 
    User findUserById(Integer id);
    resultType: 指定返回的结果类型
  -->
  <select id="findUserById" resultType="cn.tedu.spring.entity.User">
    select username name,password pw,age,id from user where id=#{id}
  </select>

<!-- 指定resultMap
    type: 指定java类的全名
    id： 唯一标识
  -->
 <resultMap type="cn.tedu.spring.entity.User" id="UserMap">
    <!-- id指定主键的对应关系，这里主键没有使用别名，因此不需要指定对应关系，可以自动对应上
    <id column="id" property="id"/> -->
    
    <!-- result ： 指定主键之外的属性
        column: 查询结果中的字段
        property：java类中的对应属性
     -->
    <result column="name" property="username"/>
    <result column="pw" property="password"/>
 </resultMap>
 
 <!-- 
    User findUserById(Integer id);
    resultMap: 指定返回的结果类型为前面定义的resultMap
  -->
  <select id="findUserById" resultMap="UserMap">
    select username name,password pw,age,id from user where id=#{id}
  </select>
​

    @Test
    public void testFinduserById() {
        //加载Spring的配置文件
        AbstractApplicationContext ac
            = new ClassPathXmlApplicationContext(
                "spring-mvc.xml",
                "spring-dao.xml");
        
        //获取UserMapper的bean，这个是spring通过扫描mapper.xml文件自动为mybatis自动创建的，首字母小写
        UserMapper userMapper
            = ac.getBean(
                "userMapper", UserMapper.class);
        
        User user=userMapper.findUserById(3);
        System.out.println(user);
        
        ac.close();
    }