    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
    015    package org.apache.tapestry5.ioc.internal.services;
    016
    017    import java.lang.ref.WeakReference;
    018    import java.util.Iterator;
    019    import java.util.List;
    020
    021    import org.apache.tapestry5.ioc.annotations.PreventServiceDecoration;
    022    import org.apache.tapestry5.ioc.internal.util.CollectionFactory;
    023    import org.apache.tapestry5.services.UpdateListener;
    024    import org.apache.tapestry5.services.UpdateListenerHub;
    025
    026    @PreventServiceDecoration
    027    public 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    }