001 // Copyright 2005 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. 014 015 package org.apache.tapestry.asset; 016 017 import java.io.BufferedInputStream; 018 import java.io.IOException; 019 import java.io.InputStream; 020 import java.net.URL; 021 import java.security.MessageDigest; 022 import java.util.HashMap; 023 import java.util.Map; 024 025 import org.apache.commons.codec.binary.Hex; 026 import org.apache.hivemind.ApplicationRuntimeException; 027 import org.apache.hivemind.ClassResolver; 028 import org.apache.hivemind.util.IOUtils; 029 import org.apache.tapestry.event.ResetEventListener; 030 031 /** 032 * Implementation of {@link org.apache.tapestry.asset.ResourceDigestSource} that calculates an 033 * DIGEST checksum digest and converts it to a string of hex digits. 034 * 035 * @author Howard M. Lewis Ship 036 * @since 4.0 037 */ 038 public class ResourceDigestSourceImpl implements ResourceDigestSource, ResetEventListener 039 { 040 private ClassResolver _classResolver; 041 042 private static final int BUFFER_SIZE = 5000; 043 044 /** 045 * Map keyed on resource path of DIGEST checksum (as a string). 046 */ 047 048 private final Map _cache = new HashMap(); 049 050 public synchronized String getDigestForResource(String resourcePath) 051 { 052 String result = (String) _cache.get(resourcePath); 053 054 if (result == null) 055 { 056 result = computeMD5(resourcePath); 057 _cache.put(resourcePath, result); 058 } 059 060 return result; 061 } 062 063 public synchronized void resetEventDidOccur() 064 { 065 _cache.clear(); 066 } 067 068 private String computeMD5(String resourcePath) 069 { 070 URL url = _classResolver.getResource(resourcePath); 071 072 if (url == null) 073 throw new ApplicationRuntimeException(AssetMessages.noSuchResource(resourcePath)); 074 075 InputStream stream = null; 076 077 try 078 { 079 MessageDigest digest = MessageDigest.getInstance("MD5"); 080 081 stream = new BufferedInputStream(url.openStream()); 082 083 digestStream(digest, stream); 084 085 stream.close(); 086 stream = null; 087 088 byte[] bytes = digest.digest(); 089 char[] encoded = Hex.encodeHex(bytes); 090 091 return new String(encoded); 092 } 093 catch (IOException ex) 094 { 095 throw new ApplicationRuntimeException(AssetMessages.unableToReadResource( 096 resourcePath, 097 ex)); 098 } 099 catch (Exception ex) 100 { 101 throw new ApplicationRuntimeException(ex); 102 } 103 finally 104 { 105 IOUtils.close(stream); 106 } 107 } 108 109 private void digestStream(MessageDigest digest, InputStream stream) throws IOException 110 { 111 byte[] buffer = new byte[BUFFER_SIZE]; 112 113 while (true) 114 { 115 int length = stream.read(buffer); 116 117 if (length < 0) 118 return; 119 120 digest.update(buffer, 0, length); 121 } 122 } 123 124 public void setClassResolver(ClassResolver classResolver) 125 { 126 _classResolver = classResolver; 127 } 128 }