    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        checksum = extraPath.substring(0, slashx);
    044
    045        String morePath = extraPath.substring(slashx + 1);
    046
    047        // Slashes at the end of the path should be dropped because
    048        // they don't make sense. TAP5-2663
    049        while (morePath.endsWith("/"))
    050        {
    051            morePath = morePath.substring(0, morePath.length() - 1);
    052        }
    053
    054        if (!isBlank(morePath))
    055        {
    056            resourcePath = baseFolder == null
    057                    ? morePath
    058                    : baseFolder + "/" + morePath;
    059        }
    060        else {
    061            // When we only have something which looks like a checksum but no actual path.
    062            // For example, /assets/META-INF/
    063            resourcePath = NON_EXISTING_RESOURCE;
    064        }
    065    }
    066
    067    /**
    068     * If the resource exists and the checksum is correct, stream it to the client and return true. Otherwise,
    069     * return false.
    070     *
    071     * @param resource
    072     *         to stream
    073     * @return true if streamed, false otherwise
    074     * @throws IOException
    075     */
    076    public boolean stream(Resource resource) throws IOException
    077    {
    078        if (resource == null || !resource.exists())
    079        {
    080            return false;
    081        }
    082
    083
    084        return streamer.streamResource(resource, checksum, ResourceStreamer.DEFAULT_OPTIONS);
    085    }
    086
    087    /**
    088     * Copied from StringUtils since it's the only method we want from it.
    089     */
    090    private static boolean isBlank(final CharSequence cs) {
    091        int strLen;
    092        if (cs == null || (strLen = cs.length()) == 0) {
    093            return true;
    094        }
    095        for (int i = 0; i < strLen; i++) {
    096            if (!Character.isWhitespace(cs.charAt(i))) {
    097                return false;
    098            }
    099        }
    100        return true;
    101    }
    102
    103}