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.commons.util.CollectionFactory;
022import org.apache.tapestry5.ioc.annotations.PreventServiceDecoration;
023import org.apache.tapestry5.ioc.services.UpdateListener;
024import org.apache.tapestry5.ioc.services.UpdateListenerHub;
025
026@PreventServiceDecoration
027public class UpdateListenerHubImpl implements UpdateListenerHub
028{
029    private final List<WeakReference<UpdateListener>> listeners = CollectionFactory.newThreadSafeList();
030
031    @Override
032    public void addUpdateListener(UpdateListener listener)
033    {
034        assert listener != null;
035        listeners.add(new WeakReference<UpdateListener>(listener));
036    }
037
038    /**
039     * Notifies all {@link UpdateListener}s.
040     */
041    @Override
042    public void fireCheckForUpdates()
043    {
044        List<WeakReference<UpdateListener>> deadReferences = CollectionFactory.newList();
045
046        Iterator<WeakReference<UpdateListener>> i = listeners.iterator();
047
048        while (i.hasNext())
049        {
050            WeakReference<UpdateListener> reference = i.next();
051
052            UpdateListener listener = reference.get();
053
054            if (listener == null)
055                deadReferences.add(reference);
056            else
057                listener.checkForUpdates();
058        }
059
060        if (!deadReferences.isEmpty())
061            listeners.removeAll(deadReferences);
062    }
063}