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 private 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 if (!isBlank(morePath)) { 048 resourcePath = baseFolder == null 049 ? morePath 050 : baseFolder + "/" + morePath; 051 } 052 else { 053 // When we only have something which looks like a checksum but no actual path. 054 // For example, /assets/META-INF/ 055 resourcePath = NON_EXISTING_RESOURCE; 056 } 057 } 058 059 /** 060 * If the resource exists and the checksum is correct, stream it to the client and return true. Otherwise, 061 * return false. 062 * 063 * @param resource 064 * to stream 065 * @return true if streamed, false otherwise 066 * @throws IOException 067 */ 068 public boolean stream(Resource resource) throws IOException 069 { 070 if (resource == null || !resource.exists()) 071 { 072 return false; 073 } 074 075 076 return streamer.streamResource(resource, checksum, ResourceStreamer.DEFAULT_OPTIONS); 077 } 078 079 /** 080 * Copied from StringUtils since it's the only method we want from it. 081 */ 082 private static boolean isBlank(final CharSequence cs) { 083 int strLen; 084 if (cs == null || (strLen = cs.length()) == 0) { 085 return true; 086 } 087 for (int i = 0; i < strLen; i++) { 088 if (!Character.isWhitespace(cs.charAt(i))) { 089 return false; 090 } 091 } 092 return true; 093 } 094 095}