001    // Copyright 2011, 2012 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.internal.services.assets;
016    
017    import org.apache.tapestry5.SymbolConstants;
018    import org.apache.tapestry5.internal.event.InvalidationEventHubImpl;
019    import org.apache.tapestry5.ioc.Resource;
020    import org.apache.tapestry5.ioc.annotations.PostInjection;
021    import org.apache.tapestry5.ioc.annotations.Symbol;
022    import org.apache.tapestry5.ioc.internal.util.URLChangeTracker;
023    import org.apache.tapestry5.ioc.services.ClasspathURLConverter;
024    import org.apache.tapestry5.services.UpdateListener;
025    import org.apache.tapestry5.services.UpdateListenerHub;
026    
027    public class ResourceChangeTrackerImpl extends InvalidationEventHubImpl implements ResourceChangeTracker,
028            UpdateListener
029    {
030        private final URLChangeTracker tracker;
031    
032        /**
033         * Used in production mode as the last modified time of any resource exposed to the client. Remember that
034         * all exposed assets include a URL with a version number, and each new deployment of the application should change
035         * that version number.
036         */
037        private final long fixedLastModifiedTime = Math.round(System.currentTimeMillis() / 1000d) * 1000L;
038    
039        public ResourceChangeTrackerImpl(ClasspathURLConverter classpathURLConverter,
040                                         @Symbol(SymbolConstants.PRODUCTION_MODE)
041                                         boolean productionMode)
042        {
043            super(productionMode);
044    
045            // Use granularity of seconds (not milliseconds) since that works properly
046            // with response headers for identifying last modified. Don't track
047            // folder changes, just changes to actual files.
048            tracker = productionMode ? null : new URLChangeTracker(classpathURLConverter, true, false);
049        }
050    
051        @PostInjection
052        public void registerWithUpdateListenerHub(UpdateListenerHub hub)
053        {
054            hub.addUpdateListener(this);
055        }
056    
057        public long trackResource(Resource resource)
058        {
059            if (tracker == null)
060            {
061                return fixedLastModifiedTime;
062            }
063    
064            return tracker.add(resource.toURL());
065        }
066    
067        public void addDependency(Resource dependency)
068        {
069            trackResource(dependency);
070        }
071    
072        public void checkForUpdates()
073        {
074            if (tracker.containsChanges())
075            {
076                fireInvalidationEvent();
077                tracker.clear();
078            }
079        }
080    
081    }