HashUtils


1   /* ***** BEGIN LICENSE BLOCK *****
2    * Version: MPL 1.1
3    * The contents of this file are subject to the Mozilla Public License Version
4    * 1.1 (the "License"); you may not use this file except in compliance with
5    * the License. You may obtain a copy of the License at
6    * http://www.mozilla.org/MPL/
7    * 
8    * Software distributed under the License is distributed on an "AS IS" basis,
9    * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
10   * for the specific language governing rights and limitations under the
11   * License.
12   * 
13   * The Original Code is Riot.
14   * 
15   * The Initial Developer of the Original Code is
16   * Neteye GmbH.
17   * Portions created by the Initial Developer are Copyright (C) 2006
18   * the Initial Developer. All Rights Reserved.
19   * 
20   * Contributor(s):
21   *   Felix Gnass [fgnass at neteye dot de]
22   * 
23   * ***** END LICENSE BLOCK ***** */
24  package org.riotfamily.common.util;
25  
26  import java.security.MessageDigest  ;
27  import java.security.NoSuchAlgorithmException  ;
28  
29  /**
30   * Utility class that simplifies the generation of MD5 fingerprints. 
31   */
32  public final class HashUtils {
33  
34      private static final String   MD5 = "MD5";
35      
36      private static MessageDigest   md5Digest;
37      
38      private HashUtils() {
39      }
40      
41      /**
42       * Hashes a String using the Md5 algorithm and returns the result as a
43       * String of hexadecimal numbers. This method is synchronized to avoid
44       * excessive MessageDigest object creation. If calling this method becomes a
45       * bottleneck in your code, you may wish to maintain a pool of MessageDigest
46       * objects instead of using this method.
47       * 
48       * @param data the String to compute the hash of.
49       * @return a hashed version of the passed-in String
50       */
51      public static synchronized String   md5(String   data) {
52          if (md5Digest == null) {
53              try {
54                  md5Digest = MessageDigest.getInstance(MD5);
55              }
56              catch (NoSuchAlgorithmException   e) {
57                  throw new RuntimeException  (e);
58              }
59          }
60          md5Digest.update(data.getBytes());
61          return toHex(md5Digest.digest());
62      }
63      
64      /**
65       * Converts an array of bytes into a String representing each byte as an
66       * unsigned hex number.
67       * 
68       * @param buffer array of bytes to convert
69       * @return generated hex string
70       */
71      public static String   toHex(byte[] buffer) {
72          StringBuffer   sb = new StringBuffer  ();
73          String   s = null;
74          for (int i = 0; i < buffer.length; i++) {
75              s = Integer.toHexString(buffer[i] & 0xff);
76              if (s.length() < 2) {
77                  sb.append('0');
78              }
79              sb.append(s);
80          }
81          return sb.toString();
82      }
83  
84  }
85
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