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1
15 package org.apache.tapestry.asset;
16
17 import java.io.BufferedInputStream  ;
18 import java.io.IOException ;
19 import java.io.InputStream ;
20 import java.net.URL ;
21 import java.security.MessageDigest ;
22 import java.util.HashMap ;
23 import java.util.Map ;
24
25 import org.apache.commons.codec.binary.Hex;
26 import org.apache.hivemind.ApplicationRuntimeException;
27 import org.apache.hivemind.ClassResolver;
28 import org.apache.hivemind.util.IOUtils;
29 import org.apache.tapestry.event.ResetEventListener;
30
31
38 public class ResourceDigestSourceImpl implements ResourceDigestSource, ResetEventListener
39 {
40 private ClassResolver _classResolver;
41
42 private static final int BUFFER_SIZE = 5000;
43
44
47
48 private final Map _cache = new HashMap ();
49
50 public synchronized String getDigestForResource(String resourcePath)
51 {
52 String result = (String ) _cache.get(resourcePath);
53
54 if (result == null)
55 {
56 result = computeMD5(resourcePath);
57 _cache.put(resourcePath, result);
58 }
59
60 return result;
61 }
62
63 public synchronized void resetEventDidOccur()
64 {
65 _cache.clear();
66 }
67
68 private String computeMD5(String resourcePath)
69 {
70 URL url = _classResolver.getResource(resourcePath);
71
72 if (url == null)
73 throw new ApplicationRuntimeException(AssetMessages.noSuchResource(resourcePath));
74
75 InputStream stream = null;
76
77 try
78 {
79 MessageDigest digest = MessageDigest.getInstance("MD5");
80
81 stream = new BufferedInputStream (url.openStream());
82
83 digestStream(digest, stream);
84
85 stream.close();
86 stream = null;
87
88 byte[] bytes = digest.digest();
89 char[] encoded = Hex.encodeHex(bytes);
90
91 return new String (encoded);
92 }
93 catch (IOException ex)
94 {
95 throw new ApplicationRuntimeException(AssetMessages.unableToReadResource(
96 resourcePath,
97 ex));
98 }
99 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 } |
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