001// Copyright 2006, 2007, 2010 The Apache Software Foundation
002//
003// Licensed under the Apache License, Version 2.0 (the "License");
004// you may not use this file except in compliance with the License.
005// You may obtain a copy of the License at
006//
007// http://www.apache.org/licenses/LICENSE-2.0
008//
009// Unless required by applicable law or agreed to in writing, software
010// distributed under the License is distributed on an "AS IS" BASIS,
011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012// See the License for the specific language governing permissions and
013// limitations under the License.
014
015package org.apache.tapestry5.ioc.internal.services;
016
017import java.lang.ref.WeakReference;
018import java.util.Iterator;
019import java.util.List;
020
021import org.apache.tapestry5.ioc.annotations.PreventServiceDecoration;
022import org.apache.tapestry5.ioc.internal.util.CollectionFactory;
023import org.apache.tapestry5.services.UpdateListener;
024import org.apache.tapestry5.services.UpdateListenerHub;
025
026@PreventServiceDecoration
027public class UpdateListenerHubImpl implements UpdateListenerHub
028{
029    private final List<WeakReference<UpdateListener>> listeners = CollectionFactory.newThreadSafeList();
030
031    public void addUpdateListener(UpdateListener listener)
032    {
033        assert listener != null;
034        listeners.add(new WeakReference<UpdateListener>(listener));
035    }
036
037    /**
038     * Notifies all {@link UpdateListener}s.
039     */
040    public void fireCheckForUpdates()
041    {
042        List<WeakReference<UpdateListener>> deadReferences = CollectionFactory.newList();
043
044        Iterator<WeakReference<UpdateListener>> i = listeners.iterator();
045
046        while (i.hasNext())
047        {
048            WeakReference<UpdateListener> reference = i.next();
049
050            UpdateListener listener = reference.get();
051
052            if (listener == null)
053                deadReferences.add(reference);
054            else
055                listener.checkForUpdates();
056        }
057
058        if (!deadReferences.isEmpty())
059            listeners.removeAll(deadReferences);
060    }
061}