    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}