Two Phase Commit

cmagno · **Posted:** Mon Dec 08, 2003 10:47 am

Hello,

I'm using Hibernate 2 and using SessionFactory to open a connection to the database.

Can I connect to two databases within one web application? And can you show me how to do it?

Two phase commit !!!! Does exist in hibernate ?????

Thanks

Carlos Magno

emmanuel · **Posted:** Mon Dec 08, 2003 11:15 am

Open 2 session factories with 2 different Configuration

2-PC exists in Hibernate if your transaction manager manage it. hibernate always delegate Transaction to etiher:
- JDBC
- JTA

cmagno · **Posted:** Tue Dec 09, 2003 8:14 am

epbernard wrote:

Open 2 session factories with 2 different Configuration

2-PC exists in Hibernate if your transaction manager manage it. hibernate always delegate Transaction to etiher:
- JDBC
- JTA

Yeah, I have used 2 session factory and 2 different configuration. Look:

Code:

public void configureTwoPhaseCommit() throws HibernateException {
    Configuration cfg = new Configuration();
    Configuration cfg2 = new Configuration();

    cfg.configure("/hibernate.cfg.xml");
    cfg2.configure("/hibernatebkp.cfg.xml"); 
      
    sessionFactory = cfg.buildSessionFactory();
    sessionFactory2 = cfg2.buildSessionFactory();
}

So, I use them here:

Code:

   public Blog createBlog(String name) throws HibernateException{
        
      Blog blog = new Blog();
      blog.setName(name);
      blog.setItems( new ArrayList() );
        
      Session session = sessionFactory.openSession();
      Session sessionBackup = sessionFactory2.openSession();
      
      Transaction tx = null;
      Transaction tx2 = null;
      try {
         tx = session.beginTransaction();
         tx2 = sessionBackup.beginTransaction();
      
         [b]session.save(blog);[/b]
         [b]sessionBackup.save(blog);[/b]
         /*
         Blog bbkp = new Blog();
         BeanUtils.copyProperties(bbkp, blog);
         sessionBackup.save(bbkp);
                           */

         tx.commit();
         tx2.commit();
         
         log.info("Blog '" + name + "' persistido");

      } catch(JDBCException e){
         if (e.getErrorCode() == 1062){
            System.out.println("Ja existe um blog com esse nome no banco, escolha outro");         
         }

      } catch (HibernateException he) {
         if (tx != null) tx.rollback();
         if (tx2 != null) tx2.rollback();
         throw he;
               
      } finally {
         session.close();
         sessionBackup.close();
      }
      return blog;
   }

session.save(blog) works fine, but sessionbkp.save(blog) throws the following exception:

Code:

Illegal attempt to associate a collection with two open sessions

Please help me !! And about transaction, am I writing the right code ?

Thank you !

emmanuel · **Posted:** Tue Dec 09, 2003 11:36 am

This is not 2-PC !
you're explicitly using 2 tx. Most time, beeing in a 2-PC means, you must be in an app server.

Your exception is due to your double association of blog to 2 different sessions. This is not allowed.

In your (highly innefficent) case

Code:

session.save(blog);
session.flush();
session.evict(blog);
sessionBackup.save(blog);
session.flush();

But opening 2 tx is definitly not 2 phase commit.

cmagno · **Posted:** Tue Dec 09, 2003 1:20 pm

epbernard wrote:

This is not 2-PC !
you're explicitly using 2 tx. Most time, beeing in a 2-PC means, you must be in an app server.

Your exception is due to your double association of blog to 2 different sessions. This is not allowed.

In your (highly innefficent) case

Code:

session.save(blog);
session.flush();
session.evict(blog);
sessionBackup.save(blog);
session.flush();

But opening 2 tx is definitly not 2 phase commit.

So, how can I do a real 2 phase commit ????

emmanuel · **Posted:** Tue Dec 09, 2003 1:43 pm

Hum, this is highly not hibernate related, and I answer this forum for free.
I recommend you :
- to read your app server on 2-PC capabilities (datasource section)
- or search commercial support on that

BTW I consider 2-Pc evil so my very best piece of advice is not to use that ;-)

Good luck.

cmagno · **Posted:** Tue Dec 09, 2003 1:53 pm

epbernard wrote:

Hum, this is highly not hibernate related, and I answer this forum for free.
I recommend you :
- to read your app server on 2-PC capabilities (datasource section)
- or search commercial support on that

BTW I consider 2-Pc evil so my very best piece of advice is not to use that ;-)

Good luck.

Sorry, my question is: Is it possible to make 2-PC with hibernate ?? Can I implement 2-PC in Hibernate programmaticly ??

Thank you for your help !! I really appreciate it.

max · **Posted:** Tue Dec 09, 2003 4:15 pm

One sessionfactory in hibernate can only work with a connection to one database at a time.

Thus, to get any kind of 2 PC, you should use 2 sessionfactories (which does allow having entities referring across each other)

Secondly - 2 PC is best used inside a J2EE container, because that is what they do!

(so the short answer is: No, Hibernate does not implement 2 PC - we do ORM)

gavin · **Posted:** Tue Dec 09, 2003 7:52 pm

Just to reiterate what everyone else is saying:

(1) of course you can use Hibernate in an environment where two-phase commit is required
(2) no, Hibernate does not itself implement 2PC - you need some other JTA implementation