public List getObjectosOrdenadosYAgrupados(Class clase, String filter,String ordering, String agrupar) {
		Collection coleccion = null;
		try {
			Class clienteClass = clase;
			Extent clnCliente = persistencia.getExtent(clienteClass, false);
			Query query = persistencia.newQuery(clnCliente, filter);
			query.setOrdering(ordering);
			query.setGrouping(agrupar);
			coleccion = (Collection) query.execute();
			return new ArrayList(coleccion);
		} catch (Exception e) {
			return null;
		}
	}