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    public void addDependency(Resource dependency)
034    {
035        long checksum = ResourceTransformUtils.toChecksum(dependency);
036
037        checksums.put(dependency, checksum);
038    }
039
040    /**
041     * Checks all resources tracked by this instance and returns true if any resource's content has changed.
042     *
043     * @return true if a change has occurred
044     */
045    public boolean dirty() throws IOException
046    {
047        for (Map.Entry<Resource, Long> e : checksums.entrySet())
048        {
049            long current = ResourceTransformUtils.toChecksum(e.getKey());
050
051            if (current != e.getValue().longValue())
052            {
053                return true;
054            }
055        }
056
057        return false;
058    }
059
060
061}