getCurrentSession与openSession的区别

1. 如果使用的是getCurrentSession来创建session的话，在commit后，session就自动被关闭了，也就是不用再session.close()了。但是如果使用的是openSession方法创建的session的话，那么必须显示的关闭session，也就是调用session.close()方法。这样commit后，session并没有关闭
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2. getCurrentSession的使用可以参见hibernate\hibernate-3.2\doc\tutorial\src项目

3.<wbr>使用SessionFactory.getCurrentSession()需要在hibernate.cfg.xml中如下配置：<br><wbr></wbr></wbr>

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* 如果采用jdbc独立引用程序配置如下：
<property name="hibernate.current_session_context_class">thread</property>
* 如果采用了JTA事务配置如下<wbr><wbr><br> &lt;property name="hibernate.current_session_context_class"&gt;jta&lt;/property&gt;</wbr></wbr>

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利于ThreadLocal模式管理Session
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早在Java1.2推出之时，Java平台中就引入了一个新的支持：java.lang.ThreadLocal，给我们在编写多线程程序
时提供了一种新的选择。ThreadLocal是什么呢？其实ThreadLocal并非是一个线程的本地实现版本，它并不是一

个Thread，
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而是thread local variable(线程局部变量)。也许把它命名为ThreadLocalVar更加合适。线程局部变量(ThreadLocal)
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其实的功用非常简单，就是为每一个使用某变量的线程都提供一个该变量值的副本，是每一个线程都可以独立地改变自己的副本，
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而不会和其它线程的副本冲突。从线程的角度看，就好像每一个线程都完全拥有一个该变量。
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ThreadLocal是如何做到为每一个线程维护变量的副本的呢？其实实现的思路很简单，在ThreadLocal类中有一个Map，用于存储每一个线程的变量的副本。比如下面的示例实现(为了简单，没有考虑集合的泛型)：

public<wbr> class<wbr> HibernateUtil<wbr></wbr></wbr></wbr>

{
<wbr><br> public static final ThreadLocal session =new ThreadLocal();<br><wbr><br> public<wbr> static<wbr> final<wbr> SessionFactory<wbr> sessionFactory;<br></wbr></wbr></wbr></wbr></wbr></wbr>

static<wbr></wbr>

{
<wbr><wbr><wbr><wbr><wbr> try<wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr> {<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> sessionFactory<wbr> =<wbr> new<wbr> Configuration().configure().buildSessionFactory();<br><wbr><wbr><wbr><wbr><wbr> }</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr> catch (Throwable<wbr> ex)</wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr> {<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr> throw<wbr> new<wbr> ExceptionInInitializerEr<wbr>ror(ex);<br><wbr><wbr><wbr><wbr><wbr> }<wbr><wbr><wbr><wbr><br><wbr>}<br><wbr><br><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

public<wbr> static<wbr> Session<wbr> currentSession()<wbr> throws<wbr> HibernateException<wbr></wbr></wbr></wbr></wbr></wbr></wbr>

{
<wbr><wbr><wbr><wbr><wbr><wbr><wbr> Session<wbr> s<wbr> =<wbr> session.get();<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> if(s<wbr> ==<wbr> null)<wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>{<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr> s<wbr> =<wbr> sessionFactory.openSession();<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr> session.set(s);<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>}<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr> return<wbr> s;<br><wbr><wbr><wbr><wbr><wbr><wbr> }</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

}

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public<wbr> static<wbr> void<wbr> closeSession()<wbr> throws<wbr> HibernateException<wbr></wbr></wbr></wbr></wbr></wbr></wbr>

{
<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>Session<wbr> s<wbr> =<wbr> session.get();<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> if(s<wbr> !=<wbr> null)<wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr> {<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr> s.close();<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> }<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> session.set(null);<br><wbr><wbr><wbr> }<br><wbr>}<br></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

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原帖地址：http://blog.sina.com.cn/s/blog_606b1aab0100diaa.html