| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| package org.apache.commons.rdf.impl.utils; |
| |
| import java.lang.ref.WeakReference; |
| import java.util.*; |
| import java.util.logging.Level; |
| import java.util.logging.Logger; |
| |
| import org.apache.commons.rdf.event.GraphEvent; |
| import org.apache.commons.rdf.event.GraphListener; |
| |
| |
| /** |
| * |
| * @author reto |
| */ |
| class DelayedNotificator { |
| |
| private static final Logger log = Logger.getLogger(DelayedNotificator.class.getName()); |
| private static Timer timer = new Timer("Event delivery timer",true); |
| |
| static class ListenerHolder { |
| |
| long delay; |
| List<GraphEvent> events = null; |
| WeakReference<GraphListener> listenerRef; |
| |
| public ListenerHolder(GraphListener listener, long delay) { |
| this.listenerRef = new WeakReference<GraphListener>(listener); |
| this.delay = delay; |
| } |
| |
| private void registerEvent(GraphEvent event) { |
| synchronized (this) { |
| if (events == null) { |
| events = new ArrayList<GraphEvent>(); |
| events.add(event); |
| timer.schedule(new TimerTask() { |
| |
| @Override |
| public void run() { |
| List<GraphEvent> eventsLocal; |
| synchronized (ListenerHolder.this) { |
| eventsLocal = events; |
| events = null; |
| } |
| GraphListener listener = listenerRef.get(); |
| if (listener == null) { |
| log.fine("Ignoring garbage collected listener"); |
| } else { |
| try { |
| listener.graphChanged(eventsLocal); |
| } catch (Exception e) { |
| log.log(Level.WARNING, "Exception delivering ImmutableGraph event", e); |
| } |
| } |
| } |
| }, delay); |
| } else { |
| events.add(event); |
| } |
| } |
| } |
| } |
| |
| private final Map<GraphListener, ListenerHolder> map = Collections.synchronizedMap( |
| new WeakHashMap<GraphListener, ListenerHolder>()); |
| |
| void addDelayedListener(GraphListener listener, long delay) { |
| map.put(listener, new ListenerHolder(listener, delay)); |
| } |
| |
| /** |
| * removes a Listener, this doesn't prevent the listenerRef from receiving |
| * events alreay scheduled. |
| * |
| * @param listenerRef |
| */ |
| void removeDelayedListener(GraphListener listener) { |
| map.remove(listener); |
| } |
| |
| /** |
| * if the listenerRef has not been registered as delayed listenerRef te events is |
| * forwarded synchroneously |
| * @param event |
| */ |
| void sendEventToListener(GraphListener listener, GraphEvent event) { |
| ListenerHolder holder = map.get(listener); |
| if (holder == null) { |
| listener.graphChanged(Collections.singletonList(event)); |
| } else { |
| holder.registerEvent(event); |
| } |
| } |
| } |