Copy Data From One Database to other using hibernate ?

[Jayaraj Jaganathan]

DDL and data are in mysql database .

we need to migrate to hsqldb.
we are having correct hbm files.

we have successful created the DDL with the help of

<property name="hibernate.hbm2ddl.auto">create</property>

now we need data. so i planned to write a event
say when there is a load in mysql it will save it in hsqldb database.

but i get "org.hibernate.HibernateException: Illegal attempt to associate a collection with two open sessions"

please help me how to solve this problem.

 
public class MigrateHibernateListener extends DefaultPostLoadEventListener   {
	
	private SessionFactory sessionFactory = null;
	
	public MigrateHibernateListener(){
		System.out.println("Event Object Created..");
		Configuration config = new Configuration();
		config.configure("config\\hibernate\\hsqldb\\hibernate.cfg.xml");
		this.sessionFactory = config.buildSessionFactory();		
	}
	
	
	public void onPostLoad(PostLoadEvent event) {
		Session session = (Session) sessionFactory.openSession();
		Transaction tx = session.getTransaction();

		try {
			tx = session.beginTransaction();
			
			migrate(session,event.getEntity());
			
			session.flush();
			
			tx.commit();

		} catch (Exception e) {
			tx.rollback();
			e.printStackTrace();
		} finally {
			session.close();
			//sessionFactory.close();
		}	
	}

	private void migrate(Session session,Object entity) throws IllegalAccessException, InstantiationException, InvocationTargetException, NoSuchMethodException {
		System.out.println("Migrating....."+entity);
		//entity = BeanUtils.cloneBean(entity);
		session.save(entity);	
	}	
}