private void startOperation() {
   session = PersistenceUtility.openSession();
   transaction = session.beginTransaction();
 }
 public void finishOperation() {
   PersistenceUtility.close(session);
 }
 private void handleException(HibernateException e) throws DataAccessLayerException {
   e.printStackTrace();
   PersistenceUtility.rollback(transaction);
   throw new DataAccessLayerException(e);
 }
 public EntityManager() {
   PersistenceUtility.buildIfNeeded();
 }