（Mybatis）单个对象的映射关系

最新推荐文章于 2025-07-14 19:04:27 发布

原创最新推荐文章于 2025-07-14 19:04:27 发布 · 781 阅读

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1、一对一：自动映射

Orders：

package com.jadan.pojo;

import java.util.Date;

public class Orders {
    private Integer id;
    private Integer userId;
    private String number;
    private Date createtime;
    private String note;

    public User getUser() {
		return user;
	}

	public void setUser(User user) {
		this.user = user;
	}

	public Integer getId() {
        return id;
    }

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

    public Integer getUserId() {
        return userId;
    }

    public void setUserId(Integer userId) {
        this.userId = userId;
    }

    public String getNumber() {
        return number;
    }

    public void setNumber(String number) {
        this.number = number == null ? null : number.trim();
    }

    public Date getCreatetime() {
        return createtime;
    }

    public void setCreatetime(Date createtime) {
        this.createtime = createtime;
    }

    public String getNote() {
        return note;
    }

    public void setNote(String note) {
        this.note = note == null ? null : note.trim();
    }
}

CustomerOrders：

package com.jadan.pojo;

import java.util.Date;

public class CustomerOrders extends Orders {
	private int uid;
	private String username;// 用户姓名
	private String sex;// 性别
	private Date birthday;// 生日
	private String address;// 地址
	
	public int getUid() {
		return uid;
	}
	public void setUid(int uid) {
		this.uid = uid;
	}
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public String getSex() {
		return sex;
	}
	public void setSex(String sex) {
		this.sex = sex;
	}
	public Date getBirthday() {
		return birthday;
	}
	public void setBirthday(Date birthday) {
		this.birthday = birthday;
	}
	public String getAddress() {
		return address;
	}
	public void setAddress(String address) {
		this.address = address;
	}
}

UserMapper.xml 映射文件：

<?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接口代理实现编写规则:
 	1. 映射文件中namespace要等于接口的全路径
 	2. 映射文件中sql语句id要等于接口的方法名
 	3. 映射文件中传入参数类型要等于接口方法的传入参数类型
 	4. 映射文件中返回结果集类型要等于接口方法的返回值类型
 -->
<mapper namespace="com.jadan.mapper.UserMapper">
    <!-- 一对一: 自动映射 -->
	<select id="findOrdersAndUser1" resultType="com.jadan.pojo.CustomerOrders">
		select o.*, u.id uid, username, birthday, sex, address 
		from orders o, user u 
		where o.user_id = u.id
	</select>
</mapper>

UserMapper.java 接口文件：

package com.jadan.mapper;

import java.util.List;
import com.jadan.pojo.CustomerOrders;

public interface UserMapper {

	// 一对一: 自动映射
	public List<CustomerOrders> findOrdersAndUser1();
	
}

UserMapperTest.java 测试文件：

package mybatis_day01;

import java.io.InputStream;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;

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 org.junit.Before;
import org.junit.Test;
import com.jadan.pojo.CustomerOrders;
import com.jadan.pojo.QueryVo;

public class UserMapperTest {
	
	private SqlSessionFactory factory;
	// 作用: 在测试方法前执行这个初始化方法
	@Before
	public void setUp() throws Exception {
		// 核心配置文件名
		String resource = "SqlMapConfig.xml";
		// 通过流将核心配置文件读取进来
		InputStream inputStream = Resources.getResourceAsStream(resource);
		// 通过核心配置文件输入流来创建会话工厂
		factory = new SqlSessionFactoryBuilder().build(inputStream);
	}
	
	// 一对一: 自动映射
	@Test
	public void testFindOrdersAndUser1() {
		SqlSession openSession = factory.openSession();
		// 通过getMapper方法来实例化接口
		UserMapper mapper = openSession.getMapper(UserMapper.class);
		
		List<CustomerOrders> list = mapper.findOrdersAndUser1();
		System.out.println(list);
	}
}

2、一对一：手动映射

Orders：（与上面的Orders多了一个user属性）

package com.jadan.pojo;

import java.util.Date;

public class Orders {
    private Integer id;
    private Integer userId;
    private String number;
    private Date createtime;
    private String note;
    private User user;

    public User getUser() {
	return user;
    }

    public void setUser(User user) {
	this.user = user;
    }

	public Integer getId() {
        return id;
    }

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

    public Integer getUserId() {
        return userId;
    }

    public void setUserId(Integer userId) {
        this.userId = userId;
    }

    public String getNumber() {
        return number;
    }

    public void setNumber(String number) {
        this.number = number == null ? null : number.trim();
    }

    public Date getCreatetime() {
        return createtime;
    }

    public void setCreatetime(Date createtime) {
        this.createtime = createtime;
    }

    public String getNote() {
        return note;
    }

    public void setNote(String note) {
        this.note = note == null ? null : note.trim();
    }
}

UserMapper.xml 映射文件：

<?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接口代理实现编写规则:
 	1. 映射文件中namespace要等于接口的全路径
 	2. 映射文件中sql语句id要等于接口的方法名
 	3. 映射文件中传入参数类型要等于接口方法的传入参数类型
 	4. 映射文件中返回结果集类型要等于接口方法的返回值类型
 -->
<mapper namespace="com.jadan.mapper.UserMapper">
<!-- 一对一: 手动映射 -->
	<!-- 
	   id: resultMap的唯一标识
	   type: 将查询出的数据放入这个指定的对象中
	         注意: 手动映射需要指定数据库中表的字段名与pojo类中属性名称对应关系
	 -->
	<resultMap type="com.jadan.pojo.Orders" id="ordersAndUserResultMap">
		<!-- id标签指定主键字段对应关系
		   column: 列,数据库中的字段名称
		   property: 属性,pojo中的属性名称
		 -->
		<id column="id" property="id"/>
		
		<!-- result: 标签指定非主键字段的对应关系 -->
		<result column="user_id" property="userId"/>
		<result column="number" property="number"/>
		<result column="createtime" property="createtime"/>
		<result column="note" property="note"/>
		
		<!-- 这个标签指定单个对象的对应关系
			 property: 指定将数据放入Orders的user属性中
			 javaType: user属性的类型
		 -->
		<association property="user" javaType="com.jadan.pojo.User">
			<id column="uid" property="id"/>
			
			<result column="username" property="username"/>
			<result column="sex" property="sex"/>
			<result column="birthday" property="birthday"/>
			<result column="address" property="address"/>
		</association> 
	</resultMap>
	<select id="findOrdersAndUser2" resultMap="ordersAndUserResultMap">
		select o.*, u.id uid, username, birthday, sex, address 
		from orders o, user u 
		where o.user_id = u.id
	</select>
</mapper>

UserMapper.java 接口文件：

package com.jadan.mapper;

import java.util.List;
import com.jadan.pojo.Orders;

public interface UserMapper {
	
	// 一对一: 手动映射
	public List<Orders> findOrdersAndUser2();
}

UserMapperTest 测试文件：

package mybatis_day01;

import java.io.InputStream;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;

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 org.junit.Before;
import org.junit.Test;

import com.jadan.mapper.UserMapper;
import com.jadan.pojo.Orders;

public class UserMapperTest {
	private SqlSessionFactory factory;
	// 作用: 在测试方法前执行这个初始化方法
	@Before
	public void setUp() throws Exception {
		// 核心配置文件名
		String resource = "SqlMapConfig.xml";
		// 通过流将核心配置文件读取进来
		InputStream inputStream = Resources.getResourceAsStream(resource);
		// 通过核心配置文件输入流来创建会话工厂
		factory = new SqlSessionFactoryBuilder().build(inputStream);
	}

        // 一对一: 手动映射
	@Test
	public void testFindOrdersAndUser2() {
		SqlSession openSession = factory.openSession();
		// 通过getMapper方法实例化接口
		UserMapper mapper = openSession.getMapper(UserMapper.class);
		
		List<Orders> list = mapper.findOrdersAndUser2();
		System.out.println(list);
	}
}

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