ResultMap结果集映射

ResultMap

ResultMap的设计思想，对于简单的语句根本不需要配置显示的结果映射，而对于复杂一点的语句只要描述它们的关系就行了。
ResultMap最优秀的地方在于，虽然你已经对它相当了解了，但是根本就不需要显式地用到他们

数据库中的字段

接口

package com.my.dao;
import com.my.pojo.User;
import java.util.List;
public interface UserMapper {
    //根据ID查询用户
    User getUserById(int id);
}

xml配置文件

<?xml version="1.0" encoding="UTF-8" ?>


    
        select * from mybatis.user where id=#{id}
   

实体类

package com.my.pojo;
//框架=设计模式+反射+注解
import org.apache.ibatis.type.Alias;
public class User {
    private int id;
    private String name;
    private String password;
    public User() {
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public User(int id, String name, String password) {
        this.id = id;
        this.name = name;
        this.password = password;
    }
    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

utils(数据库)

public class MybatisUtils {
    private static  SqlSessionFactory sqlSessionFactory;
    static{
        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public  static SqlSession getSqlSession(){
      return sqlSessionFactory.openSession();
    }

}

db.properties

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3307/mybatis?useSSL=false&useUnicode=true&characterEncoding=UTF-8
username=root
password=123456

mybatis-config.xml(核心配置文件)

<?xml version="1.0" encoding="UTF-8" ?>


    
    

    
    
        
    
    
        
            
            
            
            
                
                
                
                
            
        
    
    
   
   
    

测试类

public class UserDaoTest {
    @Test
    public void getUserLike()  {
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User user = mapper.getUserById(1);
        System.out.println(user);
        sqlSession.close();
    }

测试出现问题

select * from mybatis.user where id=#{id}等于
select id ,name,pwd from mybatis.user where id=#{id}**

解决方法一

select id ,name,pwd as password from mybatis.user where id=#{id}**
//这是将数据库中的名字作为 字段名 password来使用

解决方法二 （resultMap（结果集映射））

 id   name    pwd//数据库字段名
 id   name     password//实体类

    
        
        
        
        
    

       select id ,name,pwd    from mybatis.user where id=#{id}