    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.services.assets;
    016
    017import org.apache.commons.lang3.StringUtils;
    018import org.apache.tapestry5.internal.services.ResourceStreamer;
    019import org.apache.tapestry5.ioc.Resource;
    020
    021import java.io.IOException;
    022
    023/**
    024 * Utility used by {@link org.apache.tapestry5.services.assets.AssetRequestHandler} implementations
    025 * where the first folder in the extra path is actually a computed checksum of the resource's content.
    026 *
    027 * @since 5.4
    028 */
    029public class ChecksumPath
    030{
    031    private static final String NON_EXISTING_RESOURCE = "_________________________";
    032
    033    public final String checksum;
    034
    035    public final String resourcePath;
    036
    037    private final ResourceStreamer streamer;
    038
    039    public ChecksumPath(ResourceStreamer streamer, String baseFolder, String extraPath)
    040    {
    041        this.streamer = streamer;
    042        int slashx = extraPath.indexOf('/');
    043
    044        checksum = slashx >= 0 ? extraPath.substring(0, slashx) : null;
    045
    046        String morePath = extraPath.substring(slashx + 1);
    047
    048        if (StringUtils.isNotBlank(morePath)) {
    049            resourcePath = baseFolder == null
    050                    ? morePath
    051                    : baseFolder + "/" + morePath;
    052        }
    053        else {
    054            // When we only have something which looks like a checksum but no actual path.
    055            // For example, /assets/META-INF/
    056            resourcePath = NON_EXISTING_RESOURCE;
    057        }
    058    }
    059
    060    /**
    061     * If the resource exists and the checksum is correct, stream it to the client and return true. Otherwise,
    062     * return false.
    063     *
    064     * @param resource
    065     *         to stream
    066     * @return true if streamed, false otherwise
    067     * @throws IOException
    068     */
    069    public boolean stream(Resource resource) throws IOException
    070    {
    071        if (resource == null || !resource.exists())
    072        {
    073            return false;
    074        }
    075
    076
    077        return streamer.streamResource(resource, checksum, ResourceStreamer.DEFAULT_OPTIONS);
    078    }
    079}