Hibernate 脏数据(session.isDirty())

Hibernate 脏数据(session.isDirty())

      持久对象总是与Session和Transaction相关联，在一个Session中，对持久对象的改变不会马上对数据库进行变更，而必须在Transaction终止，也就是执行commit()之后，才在数据库中真正运行SQL进行变更，持久对象的状态才会与数据库进行同步。在同步之前的持久对象称为脏(dirty)对象。

java代码片断如下：

	public void sessionDirtyTest(){
		User user=new User();
		user.setUserid(new BigDecimal(1));               
		user.setLoginName("crabdave");        
		user.setUsername("David");         
		user.setPassword("David");         
		user.setSex("male");               
		user.setFixPhone("123456");        
		user.setMobilePhone("1234567890"); 
		user.setDeleteFlag("1");           
		user.setStatus("1");               
		user.setAge("27");                 
		user.setContract("1");             
		user.setDepartment("dept");        

		ApplicationContext ac = new FileSystemXmlApplicationContext("D:/PracticeWorkSpace/SSHPractice/src/main/resources/struts_1_spring.xml"); 
		SessionFactory sessionFactory = ((HibernateTemplate)ac.getBean("hibernateTemplate")).getSessionFactory();
		Session session=sessionFactory.openSession();
		System.out.println("1.session.isDirty():"+session.isDirty());
		Transaction tx=session.beginTransaction();
		System.out.println("2.session.isDirty():"+session.isDirty());
		tx.begin();
		System.out.println("3.session.isDirty():"+session.isDirty());
		session.update(user);
		System.out.println("4.session.isDirty():"+session.isDirty());
		tx.commit();
		System.out.println("5.session.isDirty():"+session.isDirty());
		session.close();
		System.out.println("6.session.isDirty():"+session.isDirty());
	}

运行结果如下：

1.session.isDirty():false
2.session.isDirty():false
3.session.isDirty():false
4.session.isDirty():true
Hibernate: update user set loginName=?, username=?, password=?, sex=?, fixPhone=?, mobilePhone=?, deleteFlag=?, status=?, age=?, contract=?, department=? where userid=?
5.session.isDirty():false
Exception in thread "main" org.hibernate.SessionException: Session is closed!