    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}