*/
@Override
public MutableDocumentListener createDocumentListener(String documentId) {
final Set<MutableDocumentListener> listeners = new HashSet<MutableDocumentListener>();
for (MutableDocumentListenerFactory factory : factories) {
MutableDocumentListener interestedListener = factory.createDocumentListener(documentId);
if (interestedListener != null) {
listeners.add(interestedListener);
}
}
if (!listeners.isEmpty()) {