mybatis关系映射之一对多和多对一

一. 简介:

本实例使用顾客和订单的例子做说明: 一个顾客可以有多个订单, 一个订单只对应一个顾客

二. 例子:

1. 代码结构图:

2. 建表语句:

CREATE DATABASE test;  

USE test;

CREATE TABLE person(
  personId VARCHAR(36) PRIMARY KEY,
  personName VARCHAR(64),
  personAddress VARCHAR(128),
  personTel VARCHAR(11)
);

CREATE TABLE orders(
  orderId VARCHAR(36) PRIMARY KEY,
  orderNumber VARCHAR(20),
  orderPrice INT,
  pid VARCHAR(36)
);

INSERT INTO person VALUES('001', 'Jack', 'Wuhan', '1234567');
INSERT INTO orders VALUES('O_00001', '00001', 100, '001');
INSERT INTO orders VALUES('O_00002', '00002', 200, '001');

SELECT p.*, o.*
FROM person p 
  JOIN orders o ON (p.personId=o.pid)
WHERE p.personId = '001'

3. 顾客实体:

/**
 * 客户实体 
 */
public class Person {

	private String id;
	private String name;
	private String address;
	private String tel;
	
	private List orders;
	
	@Override
	public String toString() {
		return "{id: " + id + ", name: " + name + ", address: " + address + ", tel: " + tel + "}";
	}
}

// 省略getter和setter方法

4. 订单实体:

/**
 * 订单实体
 */
public class Order {

	private String id;
	private String number;
	private int price;
	
	private Person person; 
	
	@Override
	public String toString() {
		return "{id: " + id + ", number: " + number + ", price: " + price + "}";
	}

}

// 省略getter和setter方法

5. 一对多实体配置: Person.xml

	
		
		
		
		
		
		
		
		
			
			
			
		
	
	
	
	
		select p.*, o.* from person p, orders o where p.personId  = o.pid and p.personId = #{id}
	
	

6. 多对一实体配置:

	
		
		
		
		
		
		
		
			
			
			
			
		
	
	
	
	
		select p.*, o.* from person p, orders o where p.personId  = o.pid and o.orderId = #{id}
	
	

7. 全局配置文件: sqlMapConfig.xml

8. 测试文件:

/**
 * 测试一对多和多对一
 */
public class MybatisTest {

	private SqlSessionFactory ssf; 

	@Before
	public void initSF() throws Exception {
		String resource = "sqlMapConfig.xml";
		InputStream inputStream = Resources.getResourceAsStream(resource);
		ssf = new SqlSessionFactoryBuilder().build(inputStream);
	}

	@Test//一对多关联查询
	public void selectPersonById()throws Exception{
		SqlSession session = ssf.openSession();
		Person person = session.selectOne("com.zdp.domain.Person.selectPersonById", "001");
		System.out.println(person.getOrders());
	}
	
	@Test//多对一关联查询
	public void selectOrderById()throws Exception{
		SqlSession session = ssf.openSession();
		Order order = session.selectOne("com.zdp.domain.Order.selectOrderById", "O_00001");
		System.out.println(order.getPerson().getName());
	}
}