    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.tapestry5.commons.Resource;
    018import org.apache.tapestry5.internal.services.ResourceStreamer;
    019
    020import java.io.IOException;
    021
    022/**
    023 * Utility used by {@link org.apache.tapestry5.services.assets.AssetRequestHandler} implementations
    024 * where the first folder in the extra path is actually a computed checksum of the resource's content.
    025 *
    026 * @since 5.4
    027 */
    028public class ChecksumPath
    029{
    030    static final String NON_EXISTING_RESOURCE = "_________________________";
    031
    032    public final String checksum;
    033
    034    public final String resourcePath;
    035
    036    private final ResourceStreamer streamer;
    037
    038    public ChecksumPath(ResourceStreamer streamer, String baseFolder, String extraPath)
    039    {
    040        this.streamer = streamer;
    041        int slashx = extraPath.indexOf('/');
    042
    043        if (slashx == -1) {
    044            checksum = "";
    045            resourcePath = NON_EXISTING_RESOURCE;
    046            return;
    047        }
    048
    049        checksum = extraPath.substring(0, slashx);
    050
    051        String morePath = extraPath.substring(slashx + 1);
    052
    053        // Slashes at the end of the path should be dropped because
    054        // they don't make sense. TAP5-2663
    055        while (morePath.endsWith("/"))
    056        {
    057            morePath = morePath.substring(0, morePath.length() - 1);
    058        }
    059
    060        if (!isBlank(morePath))
    061        {
    062            resourcePath = baseFolder == null
    063                    ? morePath
    064                    : baseFolder + "/" + morePath;
    065        }
    066        else {
    067            // When we only have something which looks like a checksum but no actual path.
    068            // For example, /assets/META-INF/
    069            resourcePath = NON_EXISTING_RESOURCE;
    070        }
    071    }
    072
    073    /**
    074     * If the resource exists and the checksum is correct, stream it to the client and return true. Otherwise,
    075     * return false.
    076     *
    077     * @param resource
    078     *         to stream
    079     * @return true if streamed, false otherwise
    080     * @throws IOException
    081     */
    082    public boolean stream(Resource resource) throws IOException
    083    {
    084        if (resource == null || !resource.exists())
    085        {
    086            return false;
    087        }
    088
    089
    090        return streamer.streamResource(resource, checksum, ResourceStreamer.DEFAULT_OPTIONS);
    091    }
    092
    093    /**
    094     * Copied from StringUtils since it's the only method we want from it.
    095     */
    096    private static boolean isBlank(final CharSequence cs) {
    097        int strLen;
    098        if (cs == null || (strLen = cs.length()) == 0) {
    099            return true;
    100        }
    101        for (int i = 0; i < strLen; i++) {
    102            if (!Character.isWhitespace(cs.charAt(i))) {
    103                return false;
    104            }
    105        }
    106        return true;
    107    }
    108
    109}