hibernate 单端上的lazy策略

最新推荐文章于 2026-01-09 18:49:52 发布

最新推荐文章于 2026-01-09 18:49:52 发布 · 99 阅读

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#Hibernate #SQL #Java #junit #.net

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本文探讨了Hibernate中懒加载策略的应用，特别是在单端关联上的表现。通过三个不同的测试案例，展示了如何配置实体类及其关联关系，并观察不同懒加载设置下Hibernate的行为变化。

hibernate在单端关联上的lazy策略，可以取值：false/proxy/noproxy，默认lazy=proxy

<class>标签上的lazy不会影响到单端关联上的lazy特性

1.实体类


package com.yx.zzg.bo;

public class Group {

	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;
	}
}


package com.yx.zzg.bo;

public class User {

	private int id;

	private String name;

	private Group group;

	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 Group getGroup() {
		return group;
	}

	public void setGroup(Group group) {
		this.group = group;
	}

}

2.实体类映射文件


<?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.yx.zzg.bo.User" table="t_user">
		<id name="id">
			<generator class="native"/>
		</id>
		<property name="name"/>
		<many-to-one name="group" column="groupid"/>
	</class>
</hibernate-mapping>


<?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.yx.zzg.bo.Group" table="t_group">
		<id name="id">
			<generator class="native"/>
		</id>
		<property name="name"/>
	</class>
</hibernate-mapping>

三、测试类1：SingleEndTest1.java


package com.yx.zzg.test;

import org.hibernate.Session;

import junit.framework.TestCase;
import com.yx.zzg.bo.*;

/**
 * 所有lazy属性默认
 * @author Administrator
 *
 */
public class SingleEndTest1 extends TestCase {

	public void testLoad1() {
		Session session = null;
		try {
			session = HibernateUtils.getSession();
			session.beginTransaction();

			//不会发出sql
			User user = (User)session.load(User.class, 1);

			//会发出sql
			System.out.println("user.name=" + user.getName());

			//不会发出sql
			Group group = user.getGroup();

			//会发出sql
			System.out.println("group.name=" + group.getName());

			session.getTransaction().commit();
		}catch(Exception e) {
			e.printStackTrace();
			session.getTransaction().rollback();
		}finally {
			HibernateUtils.closeSession(session);
		}
	}	

}

测试类2：SingleEndTest2.java


package com.yx.zzg.test;

import org.hibernate.Session;

import junit.framework.TestCase;

import com.yx.zzg.bo.*;

/**
 * 将<many-to-one>中的lazy设置为false,其它默认
 * @author Administrator
 *
 */
public class SingleEndTest2 extends TestCase {

	public void testLoad1() {
		Session session = null;
		try {
			session = HibernateUtils.getSession();
			session.beginTransaction();

			//不会发出sql
			User user = (User)session.load(User.class, 1);

			//会发出sql，发出两条sql分别加载User和Group
			System.out.println("user.name=" + user.getName());

			//不会发出sql
			Group group = user.getGroup();

			//不会发出sql
			System.out.println("group.name=" + group.getName());

			session.getTransaction().commit();
		}catch(Exception e) {
			e.printStackTrace();
			session.getTransaction().rollback();
		}finally {
			HibernateUtils.closeSession(session);
		}
	}	

}

测试类3：SingleEndTest3.java


package com.yx.zzg.test;

import org.hibernate.Session;

import junit.framework.TestCase;

import com.yx.zzg.bo.*

/**
 * <class>标签上的lazy=false,其它默认
 * @author Administrator
 *
 */
public class SingleEndTest3 extends TestCase {

	public void testLoad1() {
		Session session = null;
		try {
			session = HibernateUtils.getSession();
			session.beginTransaction();

			//会发出sql
			User user = (User)session.load(User.class, 1);

			//不会发出sql
			System.out.println("user.name=" + user.getName());

			//不会发出sql
			Group group = user.getGroup();

			//会发出sql
			System.out.println("group.name=" + group.getName());

			session.getTransaction().commit();
		}catch(Exception e) {
			e.printStackTrace();
			session.getTransaction().rollback();
		}finally {
			HibernateUtils.closeSession(session);
		}
	}	

}