Hibernate一对一主键单向关联

最新推荐文章于 2017-11-20 11:58:00 发布

原创最新推荐文章于 2017-11-20 11:58:00 发布 · 157 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#java

hibernate 专栏收录该内容

32 篇文章

订阅专栏

本文介绍了一种在Person表中使用主键id替代card_id作为外键的方法，以减少数据冗余并提高效率。通过Hibernate框架实现单向一对一关联，并展示了具体的Java类定义、XML映射文件及测试代码。

person表中card_id 唯一，而且还有一个主键id，这就产生了数据冗余，事实上可以同时把主键id也作为外键，可以删除原有的外键card_id,也就是单向一对一的关联可以基于主键。

Person.java类

package com.org.model;

public class Person {
	private int id;
	private String name;
	private Card card;
	
	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 Card getCard() {
		return card;
	}
	public void setCard(Card card) {
		this.card = card;
	}
	
	

}

Card.java类

package com.org.model;

public class Card {
	private int id;
	private String cardNum;
	
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getCardNum() {
		return cardNum;
	}
	public void setCardNum(String cardNum) {
		this.cardNum = cardNum;
	}
	

}

Person.hbm.xml映射文件

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.org.model">
	<class name="Person" table="person">
		<id name="id">
			<generator class="foreign">
			  <param name="property">card</param>
			</generator>
		</id>
		<property name="name" column="name" not-null="true"/>
		<!-- constrained="true"表明该类主键由关联类生成 -->
		<one-to-one name="card" constrained="true"></one-to-one>
	</class>


</hibernate-mapping>

Card.hbm.xml映射文件

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.org.model">
	<class name="Card" table="card">
		<id name="id">
			<generator class="native"/>
		</id>
		<property name="cardNum" column="card_num" not-null="true"/>
		
		
	</class>


</hibernate-mapping>

测试类：

package com.org.model.test;


import org.hibernate.Session;
import org.hibernate.Transaction;
import org.junit.Test;

import com.org.model.Card;
import com.org.model.Person;
import com.org.util.HibernateUtil;

public class HibernateTest1 {

	@Test
	public void testSave1() {
		Session session = null;
		Transaction tx = null;
		try {

			// 拿到session
			session = HibernateUtil.getSession();
			// 开启事务
			tx = session.beginTransaction();

			// 给实体赋值
			
			Person person = new Person();
			person.setName("aaa");
			Card card = new Card();
			card.setCardNum("11111111111111");
			person.setCard(card);
			session.save(person);
			

			//提交事务
			tx.commit();

		} catch (Exception e) {
			// 打印堆栈信息
			e.printStackTrace();
			// 事务回滚
			if (tx != null) {
				tx.rollback();
			}
		} finally {
			HibernateUtil.closeSession(session);
		}
	}

}

结果：

Hibernate: insert into card (card_num) values (?)
Hibernate: insert into person (name, id) values (?, ?)