Transaction tx = _odmg.currentTransaction();
openDatabase(); Transaction tx = _odmg.currentTransaction();
	public void cancelarTransaccao() throws ExcepcaoPersistencia {		try {			Transaction tx = _odmg.currentTransaction();			if (tx != null) {				tx.abort();				_odmg.getDatabase(null).close();			}		} catch (ODMGException ex1) {			throw new ExcepcaoPersistencia(				ExcepcaoPersistencia.CLOSE_DATABASE,				ex1);		} catch (ODMGRuntimeException ex) {			throw new ExcepcaoPersistencia(				ExcepcaoPersistencia.ABORT_TRANSACTION,				ex);		}	}