Hibernate的悲观锁和乐观锁

最新推荐文章于 2018-06-16 21:00:37 发布

以墨言智

最新推荐文章于 2018-06-16 21:00:37 发布

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分类专栏： Hibernate4学习总结_old

本文链接：https://blog.youkuaiyun.com/wu631464569/article/details/51273664

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本文介绍如何使用Hibernate框架实现账户实体类的数据库映射，并通过模拟取款与汇款任务来展示并发场景下的悲观锁应用。

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一，为接下来的测试添加java实体类和建立数据库映射表account:

1, 项目目录：

2、用户实体类：Account：

package com.hibtest.entity;

import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;
import org.hibernate.tool.hbm2ddl.SchemaExport;
import org.junit.Test;

/*Account账户类的测试*/
public class AccountTest {

	@Test
	public void createAccountDatabaseMapping()
	{
		//加载Hibernate的配置文件
		Configuration config = new Configuration().configure();
		
		//生成服务注册对象
		ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();
		
		//生成sessionFactory
		SessionFactory sessionFactory = config.buildSessionFactory(serviceRegistry);
		
		//获得SchemaExport
		SchemaExport schemaExport = new SchemaExport(config);
		
		//生成数据库表
		schemaExport.create(true, true);
	}
}

3，hinernate.cfg.xml配置文件：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<!-- old: http://hibernate.sourceforge.net/hibernate-configuration-3.6.dtd -->
<!-- new: http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd -->
<!--    : http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd -->
<hibernate-configuration>
<session-factory>
    <!-- 显示sql语句 -->
    <property name="show_sql">true</property>
    <property name="myeclipse.connection.profile">bookshop</property>
    <!-- <property name="connection.url">
        jdbc:mysql://localhost:3306/bookshop
        jdbc:mysql://localhost:3306/database?useUnicode=true&characterEncoding=UTF-8 
    </property> -->
    
    <property name="connection.url">jdbc:mysql://localhost:3306/hibernate?useUnicode=true&characterEncoding=UTF-8</property>
    <property name="connection.username">root</property>
    <property name="connection.password">910214</property>
    <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
    <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
    <property name="format_sql">true</property>
    <property name="hbm2ddl.auto">update</property>
    <property name="hibernate.current_session_context_class">thread</property>
    
    <!-- 将实体类映射到数据库 -->
    <!-- 
    <mapping class="oto_fk.Students"/>
    <mapping class="oto_fk.IdCard"/>
     -->
     <!-- 添加Users的数据库映射 -->
     <!-- 
    <mapping class="com.hibtest.entity.Users"/>
     -->
    <!-- <mapping class="com.hibtest.entity.IdCard"/>-->
    <!-- 添加数据库映射 -->
    <mapping class="com.hibtest.entity.Account"/>
</session-factory>
</hibernate-configuration>

4，测试文件编写：生成数据库表account:

package com.hibtest.entity;

import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;
import org.hibernate.tool.hbm2ddl.SchemaExport;
import org.junit.Test;

/*Account账户类的测试*/
public class AccountTest {

	@Test
	public void createAccountDatabaseMapping()
	{
		//加载Hibernate的配置文件
		Configuration config = new Configuration().configure();
		
		//生成服务注册对象
		ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();
		
		//生成sessionFactory
		SessionFactory sessionFactory = config.buildSessionFactory(serviceRegistry);
		
		//获得SchemaExport
		SchemaExport schemaExport = new SchemaExport(config);
		
		//生成数据库表
		schemaExport.create(true, true);
	}
}

实施生成数据库表状态截图：

数据库对应生成的表：

向account表添加测试数据：

	//向用户表Account中添加两条测试记录
	@Test
	public void insertItoAccount()
	{
		//加载Hibernate的配置文件
		Configuration config = new Configuration().configure();
		
		//生成服务注册对象
		ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();
		
		//生成sessionFactory
		SessionFactory sessionFactory = config.buildSessionFactory(serviceRegistry);
		
		//生成session对象
		Session session = sessionFactory.getCurrentSession();
		
		//获得事务并开启
		Transaction tx = session.beginTransaction();
		
		try{
			//获得两个Account对象
			Account acc1 = new Account();
			Account acc2 = new Account();
			
			acc1.setAccountNo("00000001");
			acc1.setBalance(1000);
			
			acc2.setAccountNo("00000002");
			acc2.setBalance(1000);
			
			//保存对象
			session.save(acc1);
			session.save(acc2);
			
			//提交事务
			tx.commit();
		}
		catch(HibernateException ex)
		{
			//打印异常堆栈
			ex.printStackTrace();
			//事务回滚
			tx.rollback();
		}
	}

模拟取款业务：TransactionA.java:

package com.hibtest.entity;

import java.util.TimerTask;

import org.hibernate.HibernateException;
import org.hibernate.LockMode;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;

public class TransactionA extends TimerTask {

	//模拟取款操作
		@Override
		public void run() {
			//加载Hibernate的配置文件
			Configuration config = new Configuration().configure();
			
			//生成服务注册对象
			ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();
			
			//生成sessionFactory
			SessionFactory sessionFactory = config.buildSessionFactory(serviceRegistry);
			
			//生成session对象
			Session session = sessionFactory.getCurrentSession();
			
			//获得事务并开启
			Transaction tx = session.beginTransaction();
			
			try{
				System.out.println("模拟取款任务开始： ");
				//创建HQL语句
				String hql = "from Account where Id=1";
				//创建一个Query对象
				Query query = session.createQuery(hql);
				
				//设置访问创建的对象a时的锁模式
				query.setLockMode("a", LockMode.UPGRADE_NOWAIT);//LockMode.UPGRADE_NOWAIT表示执行该select语句不成立则获得悲观锁
				
				Account acc = (Account)query.uniqueResult();
				//打印查询信息
				System.out.println("查询到的账户余额为: "+acc.getBalance());
				//将账户的余额减少100元之后
				acc.setBalance(acc.getBalance() - 100);
				System.out.println("取款100元之后： "+acc.getBalance());
				//修改执行对象
				session.update(acc);
				//提交事务
				tx.commit();
			}
			catch(HibernateException ex)
			{
				//打印异常堆栈
				ex.printStackTrace();
				//事务回滚
				tx.rollback();
			}
			
		}

}

模拟汇款任务TransactionB.java:

package com.hibtest.entity;

import java.util.TimerTask;

import org.hibernate.HibernateException;
import org.hibernate.LockMode;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;

public class TransactionB extends TimerTask {

	//模拟取款操作
		@Override
		public void run() {
			//加载Hibernate的配置文件
			Configuration config = new Configuration().configure();
			
			//生成服务注册对象
			ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();
			
			//生成sessionFactory
			SessionFactory sessionFactory = config.buildSessionFactory(serviceRegistry);
			
			//生成session对象
			Session session = sessionFactory.getCurrentSession();
			
			//获得事务并开启
			Transaction tx = session.beginTransaction();
			
			try{
				System.out.println("模拟转账任务开始： ");
				//创建HQL语句
				String hql = "from Account where Id=1";
				//创建一个Query对象
				Query query = session.createQuery(hql);
				
				//设置访问创建的对象时的锁模式
				query.setLockMode("a", LockMode.UPGRADE_NOWAIT);//LockMode.UPGRADE_NOWAIT表示执行该select语句不成立则获得悲观锁
				
				Account acc = (Account)query.uniqueResult();
				
				query.setLockMode("acc", LockMode.UPGRADE_NOWAIT);
				//打印查询信息
				System.out.println("查询到的存款账户余额为: "+acc.getBalance());
				//将账户B的余额增加100元之后
				acc.setBalance(acc.getBalance() + 100);
				System.out.println("汇款100元之后： "+acc.getBalance());
				//修改执行对象
				session.update(acc);
				//提交事务
				tx.commit();
			}
			catch(HibernateException ex)
			{
				//打印异常堆栈
				ex.printStackTrace();
				//事务回滚
				tx.rollback();
			}
			
		}

}

实施取款汇款业务：

package com.hibtest.entity;

import java.util.Timer;

public class testTransactionAB {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		new testTransactionAB().testGetSet();
	}
	
	public void testGetSet()
	{
		//悲观锁，分别通过定时器启动事务A和事务B
		Timer timer1 = new Timer();
		//立即启动事务A的线程
		timer1.schedule(new TransactionA(),0);
		
		Timer timer2 = new Timer();
		//立即启动事务B的线程
		timer2.schedule(new TransactionB(),0);
	}

}

后台打印的log：

模拟取款任务开始： 
模拟转账任务开始： 
Hibernate: 
    select
        account0_.id as id0_,
        account0_.accountNo as accountNo0_,
        account0_.balance as balance0_ 
    from
        Account account0_ 
    where
        Id=1
Hibernate: 
    select
        account0_.id as id0_,
        account0_.accountNo as accountNo0_,
        account0_.balance as balance0_ 
    from
        Account account0_ 
    where
        Id=1
查询到的账户余额为: 1000
取款100元之后： 900
查询到的存款账户余额为: 1000
汇款100元之后： 1100
Hibernate: 
    update
        Account 
    set
        accountNo=?,
        balance=? 
    where
        id=?
Hibernate: 
    update
        Account 
    set
        accountNo=?,
        balance=? 
    where
        id = ？