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006——hibernate一对一关联映射

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一对一关联映射有两种方式：主键关联和外键关联

以夫妻为例（Husband----Wife）

单向关联实体类：

Husband.java 

package com.java.hibernate;

public class Husband {
	
	private int id;
	
	private String name;
	
	private Wife wife;

	public Wife getWife() {
		return wife;
	}

	public void setWife(Wife wife) {
		this.wife = wife;
	}

	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;
	}
	
}

Wife.java 

package com.java.hibernate;

public class Wife {

	private int id;
	
	private String name;

	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;
	}
	
}

双向关联实体类：

Husband.java 

package com.java.hibernate;

public class Husband {
	
	private int id;
	
	private String name;
	
	private Wife wife;

	public Wife getWife() {
		return wife;
	}

	public void setWife(Wife wife) {
		this.wife = wife;
	}

	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;
	}
	
}

Wife.java 

package com.java.hibernate;

public class Wife {

	private int id;
	
	private String name;
	
	private Husband husband;

	public Husband getHusband() {
		return husband;
	}

	public void setHusband(Husband husband) {
		this.husband = husband;
	}

	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;
	}
	
}

单向主键关联：

Husband映射文件： 

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
	<class name="com.java.hibernate.Husband" table="t_husband">
		<id name="id">
			<!-- 采用foreign生成策略，forgeign会取得关联对象的标识 -->
			<generator class="foreign">
				<!-- property只关联对象 -->
				<param name="property">wife</param>
			</generator>		
		</id>
		<property name="name"></property>
		<!-- 
			one-to-one指示hibernate如何加载其关联对象，默认根据主键加载
			也就是拿到关系字段值，根据对端的主键来加载关联对象
		
			constrained="true表示，当前主键(husband的主键)还是一个外键
			参照了对端的主键（wife的主键），也就是会生成外键约束语句
		 -->
		<one-to-one name="wife" constrained="true"/>
	</class>
</hibernate-mapping>
Wife映射文件： 
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
	
<hibernate-mapping>
	<class name="com.java.hibernate.Wife" table="t_wife">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="name"></property>
	</class>
</hibernate-mapping>
测试类
package com.java.hibernate;

import junit.framework.TestCase;

import org.hibernate.Session;

public class Test extends TestCase{
	
	public void testSave1() {
		Session session = null;
		try {
			session = HibernateUtils.getSession();
			session.beginTransaction();
			
			Wife wife = new Wife();
			wife.setName("昆凌");
			
			Husband husband = new Husband();
			husband.setName("周杰伦");
			//建立关联
			husband.setWife(wife);
			//没有抛出TransientObjectException
			//是由一对一关联映射的特性决定的，它必须先保存关联对象wife
			//这样它采用foreign映射策略才能取得关联对象的标识
			//也就是它默认了cascade属性
			session.save(husband);
			session.getTransaction().commit();
		} catch (Exception e) {
			e.printStackTrace();
			session.getTransaction().rollback();
		} finally {
			HibernateUtils.closeSession(session);
		}
	}
	
	public void testSave2() {
		Session session = null;
		try {
			session = HibernateUtils.getSession();
			session.beginTransaction();
			
			Wife wife = new Wife();
			wife.setName("昆凌");
			
			Husband husband = new Husband();
			husband.setName("周杰伦");
			//建立关联
			husband.setWife(wife);
			//只能将IdCard保存，不能将Person保存
			//因为关系的维护端在Person端，IdCard不知道Person的存在
			session.save(wife);
			session.getTransaction().commit();
		} catch (Exception e) {
			e.printStackTrace();
			session.getTransaction().rollback();
		} finally {
			HibernateUtils.closeSession(session);
		}
	}

	public void testLoad1() {
		Session session = null;
		try {
			session = HibernateUtils.getSession();
			session.beginTransaction();
			Husband husband = (Husband)session.load(Husband.class, 1);
			System.out.println("husband.name=" + husband.getName());
			System.out.println("husband.wife=" + husband.getWife().getName());
			session.getTransaction().commit();
		}catch(Exception e) {
			e.printStackTrace();
			session.getTransaction().rollback();
		}finally {
			HibernateUtils.closeSession(session);
		}
	}
	
}

双向主键关联：

参照单向主键关联，只需修改Wife映射文件：

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
	
<hibernate-mapping>
	<class name="com.java.hibernate.Wife" table="t_wife">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="name"></property>
		<one-to-one name="husband"></one-to-one>
	</class>
</hibernate-mapping>
测试类：
package com.java.hibernate;

import junit.framework.TestCase;

import org.hibernate.Session;

public class Test extends TestCase {
	
	public void testLoad() {
		Session session = null;
		try {
			session = HibernateUtils.getSession();
			session.beginTransaction();
			
			Wife wife = (Wife) session.load(Wife.class, 1);
			System.out.println(wife.getName());
			System.out.println(wife.getHusband().getName());
			
			session.getTransaction().commit();
		} catch (Exception e) {
			e.printStackTrace();
			session.getTransaction().rollback();
		} finally {
			HibernateUtils.closeSession(session);
		}
		
	}
	
}

单向外键关联：

一对一唯一外键关联映射其实是多对一的特例，采用<many-to-one>标签来映射，指定多的一端unique为true，这样就限制了多的一端的多重性唯一，就是这样来映射的。

Husband映射文件

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
	<class name="com.java.hibernate.Husband" table="t_husband">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="name"></property>
		<many-to-one name="wife" unique="true"></many-to-one>
	</class>
</hibernate-mapping>

Wife映射文件

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
	
<hibernate-mapping>
	<class name="com.java.hibernate.Wife" table="t_wife">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="name"></property>
	</class>
</hibernate-mapping>

测试类

package com.java.hibernate;

import junit.framework.TestCase;

import org.hibernate.Session;

public class Test extends TestCase{
	
	public void testSave1() {
		Session session = null;
		try {
			session = HibernateUtils.getSession();
			session.beginTransaction();
			
			Wife wife = new Wife();
			wife.setName("昆凌");
			
			Husband husband = new Husband();
			husband.setName("周杰伦");
			//建立关联
			husband.setWife(wife);
			//抛出TransientObjectException
			//因为IdCard为Transient状态
			session.save(husband);
			session.getTransaction().commit();
		} catch (Exception e) {
			e.printStackTrace();
			session.getTransaction().rollback();
		} finally {
			HibernateUtils.closeSession(session);
		}
	}
	
	public void testSave2() {
		Session session = null;
		try {
			session = HibernateUtils.getSession();
			session.beginTransaction();
			
			Wife wife = new Wife();
			wife.setName("昆凌");
			session.save(wife);
			
			Husband husband = new Husband();
			husband.setName("周杰伦");
			//建立关联
			husband.setWife(wife);
		
			session.save(husband);
			session.getTransaction().commit();
		} catch (Exception e) {
			e.printStackTrace();
			session.getTransaction().rollback();
		} finally {
			HibernateUtils.closeSession(session);
		}
	}

	public void testLoad1() {
		Session session = null;
		try {
			session = HibernateUtils.getSession();
			session.beginTransaction();
			Husband husband = (Husband)session.load(Husband.class, 2);
			System.out.println("husband.name=" + husband.getName());
			System.out.println("husband.wife=" + husband.getWife().getName());
			session.getTransaction().commit();
		}catch(Exception e) {
			e.printStackTrace();
			session.getTransaction().rollback();
		}finally {
			HibernateUtils.closeSession(session);
		}
	}
	
}

双向外键关联：

一对一唯一外键关联双向采用<one-to-one>标签映射，必须指定<one-to-one>标签中的property-ref属性为关系字段的名称

参照单向外键关联，只需修改Wife映射 文件

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
	
<hibernate-mapping>
	<class name="com.java.hibernate.Wife" table="t_wife">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="name"></property>
		<one-to-one name="husband" property-ref="wife"></one-to-one>
	</class>
</hibernate-mapping>
测试类： 

package com.java.hibernate;

import junit.framework.TestCase;

import org.hibernate.Session;

public class Test extends TestCase {
	
	public void testLoad() {
		Session session = null;
		try {
			session = HibernateUtils.getSession();
			session.beginTransaction();
			
			Wife wife = (Wife) session.load(Wife.class, 1);
			System.out.println(wife.getName());
			System.out.println(wife.getHusband().getName());
			
			session.getTransaction().commit();
		} catch (Exception e) {
			e.printStackTrace();
			session.getTransaction().rollback();
		} finally {
			HibernateUtils.closeSession(session);
		}
		
	}
	
}

原文：http://blog.csdn.net/msj_god_boy/article/details/51931231

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