java - Hibernate openSession() vs getCurrentSession()

Question

I have some questions about using Hibernate in JSP web application.

1. What should be the value for hibernate.current_session_context_class?

2. Then, which of the following statements should be used? And why?

    Session s = HibernateUtil.getSessionFactory().openSession();
    Session s = HibernateUtil.getSessionFactory().getCurrentSession()
   

3. Lastly, which one is better "one session per web app" or "one session per request"?

Answer 1

As explained in this forum post, 1 and 2 are related. If you set hibernate.current_session_context_class to thread and then implement something like a servlet filter that opens the session - then you can access that session anywhere else by using the SessionFactory.getCurrentSession().

SessionFactory.openSession() always opens a new session that you have to close once you are done with the operations. SessionFactory.getCurrentSession() returns a session bound to a context - you don't need to close this.

If you are using Spring or EJBs to manage transactions you can configure them to open / close sessions along with the transactions.

You should never use one session per web app - session is not a thread safe object - cannot be shared by multiple threads. You should always use "one session per request" or "one session per transaction"