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openSession() or getCurrentSession()?

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juanita

Post subject: openSession() or getCurrentSession()?

Posted: Thu Mar 01, 2007 11:52 am

Beginner

Joined: Wed Jan 31, 2007 11:39 am
Posts: 24

I would like to ask a question about Session. For example in a DAO method I start using session like that:

Code:

session = HibernateUtil.getSessionFactory().openSession();

When I did not use the above and used:

Code:

session = HibernateUtil.getSessionFactory().getCurrentSession()

I had problems.But I guess using the openSession() everytime is not correct right?

My hibernate Util is:

Code:

public class HibernateUtil {
    private static final SessionFactory sessionFactory;
    static {
        try {
            // Create the SessionFactory from hibernate.cfg.xml
            sessionFactory = new Configuration().configure().buildSessionFactory();
        } catch (Throwable ex) {
            // Make sure you log the exception, as it might be swallowed
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }

    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }

}

I guess I should add a method like getSession() that will open a session
(openSession()) only if getCurrentSession is not null?

Please some suggestions..

...Thanks

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joijoe

Post subject:

Posted: Fri Mar 02, 2007 5:52 am

Newbie

Joined: Fri Nov 03, 2006 5:21 am
Posts: 14

Hi,

I'd use getCurrentSession() as this method opens a new session if no session exists so war but it uses an existing session if there already exists one.

I assume that you only want to have one session in your application.

Another advantage of getCurrentSession() is that it manages it sessions with a transaction manager in a J2EE application. I.e. the session is automatically bound to the transaction and is fushed before the transaction commits. and if a parallel transaction is opened you automatically get a new session.

In case of a standalone application that doesn't use a transaction manager, make sure that you bind your session to the thread using the property
<property name="current_session_context_class">thread</property>
in your hibernate.cfg.xml.

Regards,
Joern

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juanita

Post subject:

Posted: Fri Mar 02, 2007 6:14 am

Beginner

Joined: Wed Jan 31, 2007 11:39 am
Posts: 24

I am using Hibernate 3.2 with Tomcat. I am having the JTATransactionManager since Tomcat does not have one, and the transaction.manager_lookup_class is the org.hibernate.transaction.JOTMTransactionManagerLookup.

I read that if I use Hibernate 3.x (a more advanced than 3.0) the sessionFactory.getCurrentSession() is all I need for session.
But I have a null pointer exception.The method works only if I use the openSession().

Here is my code in my UserDao:

Code:

session = HibernateUtil.getSessionFactory().getCurrentSession();
Context ctx = new InitialContext();
tx =         (UserTransaction)ctx.lookup("java:comp/env/UserTransaction");          
tx.begin();        
session.get(User.class, new Long(1));
tx.commit();      
session.close()

Is the order of Session and transaction correct?
If I open first the transaction and then get session I have :

Code:

org.hibernate.HibernateException: get is not valid without active transaction

Any suggestions?

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joijoe

Post subject:

Posted: Fri Mar 02, 2007 10:01 am

Newbie

Joined: Fri Nov 03, 2006 5:21 am
Posts: 14

Hi,

have you set the configuration parameter

Code:

If yes, you should first start the UserTransaction and afterwards call the getCurrentSession() method.

Hope this helps,
Joern[/quote]

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joijoe

Post subject:

Posted: Fri Mar 02, 2007 10:02 am

Newbie

Joined: Fri Nov 03, 2006 5:21 am
Posts: 14

Hi,

have you set the configuration parameter

Code:

If yes, you should first start the UserTransaction and afterwards call the getCurrentSession() method.

Hope this helps,
Joern[/quote]

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