Hibernate rollback not acting as expected

Hibernate ORM
1 
        SessionFactory sessionFactory = HBConfig.sessionFactory();
        Transaction transaction = null;
        Session session = sessionFactory.openSession();
        try {
            transaction = session.beginTransaction();
            User user = new User("salib", "ss@ss", "ss", Role.ADMIN);
            session.save(user);
            User user2 = session.createQuery("from User u where id = 2", User.class).getSingleResult();
            transaction.commit();
            session.close();
        }
        catch (Exception ex) {
            if (transaction != null) {
                transaction.rollback();
            }
        }

In the above code, session.createQuery statement throws exception as there is no user with id 2 in the database. then it comes to catch block and executes transaction.rollback() statement. after that, i checked the db and found the saved user in the user table. how is that happend? the transaction was rollbacked properly int the code. FlashMode was auto and I suppose it flushed before the execution of the query but it was never committed.

2

The only possible explanation I have is that you configured auto-commit for your database connections but also messed with how Hibernate ORM resets the auto-commit status.
If you enable hibernate.connection.provider_disables_autocommit, then Hibernate won’t set auto-commit to false. If your connection provider fails to set auto-commit to false though, you’ll be in trouble.