5.Hibernate的一对一唯一外键关联映射

 一对一唯一外键关联映射实际上是多对一关联映射的特例。

 

可以采用many-to-one标签，指定多的一端的unique=true,这样就限制了多的一端的多重性唯一。

通过这种手段映射一对一唯一外键关联。

<many-to-one name="idCard"  unique= "true" />

 

一对一唯一外键关联双向，需要在另一端（idCard），添加<one-to-one>标签，指示hibernate如何加载其关联对象，默认根据主键加载，外键关联映射中，因为两个实体采用的是person外键维护的关系，所以不能指定主键加载person，而要根据person的外键加载，所以采用如下映射方式：

<one-to-one name="person" property-ref="idCard">

 

一：实体类：

package com.tao.hibernate.one2one2;

public class IdCard2 {
	private Integer id;
	private String cardNo;
	private Person2 person;

	public IdCard2() {
		super();
	}

	public Integer getId() {
		return id;
	}

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

	public String getCardNo() {
		return cardNo;
	}

	public void setCardNo(String cardNo) {
		this.cardNo = cardNo;
	}

	public Person2 getPerson() {
		return person;
	}

	public void setPerson(Person2 person) {
		this.person = person;
	}

}

 

package com.tao.hibernate.one2one2;


public class Person2 {
	private Integer id;
	private String name;
	private IdCard2 idCard;

	public Person2() {
		super();
	}

	public Integer getId() {
		return id;
	}

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

	public String getName() {
		return name;
	}

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

	public IdCard2 getIdCard() {
		return idCard;
	}

	public void setIdCard(IdCard2 idCard2) {
		this.idCard = idCard2;
	}

}

 

二：映射文件：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.tao.hibernate.one2one2">
	<class name="IdCard2" table="t_IdCard2">
		<id name="id" column="id" type="integer">
			<generator class="native" />
		</id>
		<property name="cardNo" column="cardNo" />
		<one-to-one name="person" property-ref="idCard" />
	</class>
</hibernate-mapping>

 

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.tao.hibernate.one2one2">
	<class name="Person2" table="t_Person2">
		<id name="id" column="id" type="integer">
			<generator class="native">
			</generator>
		</id>
		<property name="name" column="name" />
		<many-to-one name="idCard" unique="true"/>
	</class>
</hibernate-mapping>

 

三：测试类：

package com.tao.hibernate.one2one2;

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

import com.tao.hibernate.HibernateUtils;

public class TestMain {

	@Test
	public void testSave() {
		Session session = HibernateUtils.getFactory().openSession();

		IdCard2 idCard = new IdCard2();
		idCard.setCardNo("100");

		Person2 person = new Person2();
		person.setName("Tao");
		person.setIdCard(idCard);

		Transaction ts = session.beginTransaction();
		ts.begin();
		session.save(idCard);
		session.save(person);
		ts.commit();
	}

	@Test
	public void testLoad() {
		Session session = HibernateUtils.getFactory().openSession();
		Person2 person = (Person2) session.load(Person2.class, 1);
		//System.out.println(person.getName());
		System.out.println(person.getIdCard().getCardNo());
	}

	@Test
	public void testLoad2() {
		Session session = HibernateUtils.getFactory().openSession();
		IdCard2 idCard = (IdCard2) session.load(IdCard2.class, 1);
		System.out.println(idCard.getCardNo());
		System.out.println(idCard.getPerson().getName());
	}

}