Hibernate one-to-many

1数据库开发中经常会遇到一对多的关系，例如客户与订单的关系，一个客户对应多个订单。

开发一个customer与orders的demo

（1）领域模型

customer

package com.songxu.domain;

import java.io.Serializable;
import java.util.Set;

public class Customer implements Serializable
{
	private int id;
	private String name;
	private Set orders;
	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 Set getOrders()
	{
		return orders;
	}
	public void setOrders(Set orders)
	{
		this.orders = orders;
	}

}

orders

package com.songxu.domain;

import java.io.Serializable;
import java.sql.Timestamp;

public class Order implements Serializable
{
	private int id;
	private Timestamp time;
	
	private Customer customer;

	public int getId()
	{
		return id;
	}

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

	public Timestamp getTime()
	{
		return time;
	}

	public void setTime(Timestamp time)
	{
		this.time = time;
	}

	public Customer getCustomer()
	{
		return customer;
	}

	public void setCustomer(Customer customer)
	{
		this.customer = customer;
	}

}

(2) hbm 映射文件

customer

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
                                   "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
 <class name="com.songxu.domain.Customer" table="customer">
  <id column="id" name="id" type="int">
   <generator class="increment"/>
  </id>
  <!-- column同名时可以省略 -->
  <property column="name" generated="never" lazy="false" name="name" type="string"/>
  <set name="orders" cascade="save-update" inverse="true" >
  
  <key column="customer" ></key>
  <one-to-many class="com.songxu.domain.Order"/>
  </set>
 </class>
</hibernate-mapping>

order

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
                                   "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
 <class name="com.songxu.domain.Order" table="orders">
  <id column="id" name="id" type="int">
   <generator class="increment"/>
  </id>
  <!-- column同名时可以省略 -->
  <property column="occurTime" generated="never" lazy="false" name="time" type="timestamp"/>
  <many-to-one name="customer" class="com.songxu.domain.Customer" column="customer_id"></many-to-one>
	
 </class>
</hibernate-mapping>

2 自身一对多的例子，如层次关系

（1） 领域模型

package com.songxu.domain;

import java.util.Set;

public class Food
{
	private int id;
	private String name ;
	private Food parentFood;
	private Set<Food> childFood;
	public int getId()
	{
		return id;
	}
	public Food()
	{
		
	}
	public Food(String name, Food parentFood, Set<Food> childFood)
	{
	
		this.name = name;
		this.parentFood = parentFood;
		this.childFood = childFood;
	}
	public void setId(int id)
	{
		this.id = id;
	}
	public String getName()
	{
		return name;
	}
	public void setName(String name)
	{
		this.name = name;
	}
	public Food getParentFood()
	{
		return parentFood;
	}
	public void setParentFood(Food parentFood)
	{
		this.parentFood = parentFood;
	}
	public Set<Food> getChildFood()
	{
		return childFood;
	}
	public void setChildFood(Set<Food> childFood)
	{
		this.childFood = childFood;
	}

}

（2） 映射文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
                                   "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
	<class name="com.songxu.domain.Food" table="food">
		<id column="id" name="id" type="int">
			<generator class="increment" />
		</id>
		<!-- column同名时可以省略 -->
		<property column="name" generated="never" lazy="false" name="name"
			type="string" />

		<many-to-one name="parentFood" class="com.songxu.domain.Food"
			column="foodId"></many-to-one>
		<set name="childFood" cascade="all">
			<key column="foodId"></key>
			<one-to-many class="com.songxu.domain.Food" />


		</set>


	</class>
</hibernate-mapping>

（3） 测试代码

package com.songxu.test;

import java.util.HashSet;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

import com.songxu.domain.Food;

public class FoodTest
{
	static Configuration configuration;
	static SessionFactory sessionFactory;
	static
	{
		configuration=new Configuration().configure();
		sessionFactory=configuration.buildSessionFactory();
	}
	public static void main(String[] args)
	{
		Session session=sessionFactory.openSession();
		Transaction tx=null;
		try
		{
			tx=session.beginTransaction();
			
			
			Food food=new Food("食品",null,new HashSet<Food>());
			
			Food fruit=new Food("水果",null,new HashSet<Food>());
			Food vegetables=new Food("蔬菜",null,new HashSet<Food>());
			
			food.getChildFood().add(fruit);
			food.getChildFood().add(vegetables);
			fruit.setParentFood(food);
			vegetables.setParentFood(food);
			
			
			Food fruit1=new Food("苹果",null,new HashSet<Food>());
			Food fruit2=new Food("香蕉",null,new HashSet<Food>());
			Food v1=new Food("黄瓜",null,new HashSet<Food>());
			Food v2=new Food("茄子",null,new HashSet<Food>());
			
			fruit.getChildFood().add(fruit1);
			fruit.getChildFood().add(fruit2);
			fruit1.setParentFood(fruit);
			fruit2.setParentFood(fruit);
			
			
			
			vegetables.getChildFood().add(v1);
			vegetables.getChildFood().add(v2);
			v1.setParentFood(vegetables);
			v2.setParentFood(vegetables);
			
			//仅保存根对象就可以了
			session.save(food);
			
			
			//session.get(Food.class,1);
			tx.commit();
			
			
			
			
			
			
			
			
			
			
			
			
			
			
			
			
			
			
			
		}
		catch (Exception e)
		{
			
			if(null!=tx)
			{
				tx.rollback();
			}
			e.printStackTrace();
		
		}
		
		finally
		{
			session.close();
		}
	}

}

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