Guarantee SessionFactory doesn't re-use Sessions

tsm1mt · **Posted:** Sat Apr 08, 2006 1:37 am

Hibernate version: 3

Name and version of the database you are using: Oracle 10g-RAC

I'm using one-user, one-connection to the Oracle DB, and went down the path of starting a single (Long) Hibernate Session (and DB connection) at login and retain it throughout the user's use of the application. (Struts/JSP web-app)

Works fine with a single user, but during system testing we found problems with more than one concurrent user.

The SessionFactory is re-assigning existing HibernateSessions, which results in numerous problems like duplicate-collections, flushed/evicted collections, etc. when two users share a Hibernate Session and perform similar (or incompatible) tasks.

If everyone has their own Hibernate Session, all is well. It seems if someone is actively using their session (performing a task), the Factory assigns any new users a different Session.

Allow your Session to sit idle for a minute, and it might get "borrowed" by the next person to log in.

At this point, I think I need to dig up the source code for HibernateSessionFactory and modify it to never re-use a Session.

Or is there a simpler way to guarantee the SessionFactory returns a given Session once, and only once?

I'm already managing that the user gets and keeps his/her HibSession throughout their use of the application - I just didn't expect two users to be given the same Session object.

max · **Posted:** Sat Apr 08, 2006 5:10 am

huh ? SessionFactory *never* returns the same session twice.

(currentSession can do that though, but that is the whole point of that method)

tsm1mt · **Posted:** Sat Apr 08, 2006 1:22 pm

OK, the DAOs, etc. all call my HibernateSessionFactory.currentSession()

currentSession() looks like this:

Code:

public static Session currentSession() throws HibernateException {
           Session session = (Session) threadLocal.get();
           if (session == null || session.isOpen() == false) {
               if (sessionFactory == null) {
                   try {
                       cfg.configure(CONFIG_FILE_LOCATION);
                       sessionFactory = cfg.buildSessionFactory();
                   }
                   catch (Exception e) {
                       System.err.println("%%%% Error Creating SessionFactory %%%%");
                       e.printStackTrace();
                   }
               }
               session = sessionFactory.openSession();
               threadLocal.set(session);
           }
           return session;
       }

Before any DAOs make an attempt to call "currentSession", I pull the Hibernate Session from the HTTP Session and force the threadLocal referenced above to be the "existing HibSession fetched from the HttpSession"

Thus, the currentSession() reads: "if the threadlocal wasn't already set, retrieve a new hibSession object"

Typically, that only happens at login, when the user doesn't have a Hibernate Session yet.

My problem is that it frequently winds up assigning the same Hibernate Session to TWO (or a dozen) User/HttpSessions.

Then I wind up with "two collections with same identifier already in Session" and "object was already evicted" or "already flushed" problems from two people playing in the same sandbox.

I'll double check and put the session.hashCode out to the log file anytime "openSession" is called and see if it IS returning a different one each time and somewhere I'm fouling it up.

baliukas · **Posted:** Sat Apr 08, 2006 4:29 pm

Just do not store hibernate session in http session, it can not work on heavy load.

baliukas · **Posted:** Sat Apr 08, 2006 4:35 pm

BTW it looks like you do not clear thread local and it is reused for next user.