001// Copyright 2013 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.internal.webresources;
016
017import org.apache.tapestry5.ioc.Resource;
018import org.apache.tapestry5.ioc.internal.util.CollectionFactory;
019import org.apache.tapestry5.services.assets.ResourceDependencies;
020
021import java.io.IOException;
022import java.util.Map;
023
024/**
025 * Manages a collection of Resources and can check to see if any resource's actual content has changed.
026 *
027 * @since 5.4
028 */
029public class ContentChangeTracker implements ResourceDependencies
030{
031    private final Map<Resource, Long> checksums = CollectionFactory.newMap();
032
033    @Override
034    public void addDependency(Resource dependency)
035    {
036        long checksum = ResourceTransformUtils.toChecksum(dependency);
037
038        checksums.put(dependency, checksum);
039    }
040
041    /**
042     * Checks all resources tracked by this instance and returns true if any resource's content has changed.
043     *
044     * @return true if a change has occurred
045     */
046    public boolean dirty() throws IOException
047    {
048        for (Map.Entry<Resource, Long> e : checksums.entrySet())
049        {
050            long current = ResourceTransformUtils.toChecksum(e.getKey());
051
052            if (current != e.getValue().longValue())
053            {
054                return true;
055            }
056        }
057
058        return false;
059    }
060
061
062}