1   /**
2    * Copyright (c) 2000-2010 Liferay, Inc. All rights reserved.
3    *
4    * This library is free software; you can redistribute it and/or modify it under
5    * the terms of the GNU Lesser General Public License as published by the Free
6    * Software Foundation; either version 2.1 of the License, or (at your option)
7    * any later version.
8    *
9    * This library is distributed in the hope that it will be useful, but WITHOUT
10   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
11   * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
12   * details.
13   */
14  
15  package com.liferay.portal.servlet.filters.etag;
16  
17  import com.liferay.portal.kernel.servlet.HttpHeaders;
18  import com.liferay.portal.kernel.util.GetterUtil;
19  import com.liferay.portal.util.PropsUtil;
20  
21  import javax.servlet.http.HttpServletRequest;
22  import javax.servlet.http.HttpServletResponse;
23  
24  /**
25   * <a href="ETagUtil.java.html"><b><i>View Source</i></b></a>
26   *
27   * @author Brian Wing Shun Chan
28   * @author Shuyang Zhou
29   */
30  public class ETagUtil {
31  
32      public static boolean processETag(
33          HttpServletRequest request, HttpServletResponse response,
34          byte[] bytes) {
35  
36          if (!_ETAG_FILTER_ENABLED) {
37              return false;
38          }
39  
40          return _processETag(
41              request, response, _hashCode(bytes, 0, bytes.length));
42      }
43  
44      public static boolean processETag(
45          HttpServletRequest request, HttpServletResponse response, byte[] bytes,
46          int length) {
47  
48          if (!_ETAG_FILTER_ENABLED) {
49              return false;
50          }
51  
52          return _processETag(request, response, _hashCode(bytes, 0, length));
53      }
54  
55      public static boolean processETag(
56          HttpServletRequest request, HttpServletResponse response, byte[] bytes,
57          int offset, int length) {
58  
59          if (!_ETAG_FILTER_ENABLED) {
60              return false;
61          }
62  
63          return _processETag(
64              request, response, _hashCode(bytes, offset, length));
65      }
66  
67      public static boolean processETag(
68          HttpServletRequest request, HttpServletResponse response, String s) {
69  
70          if (!_ETAG_FILTER_ENABLED) {
71              return false;
72          }
73  
74          return _processETag(request, response, s.hashCode());
75      }
76  
77      private static int _hashCode(byte[] data, int offset, int length) {
78          int hashCode = 0;
79  
80          for (int i = 0; i < length; i++) {
81              hashCode = 31 * hashCode + data[offset++];
82          }
83  
84          return hashCode;
85      }
86  
87      private static boolean _processETag(
88          HttpServletRequest request, HttpServletResponse response,
89          int hashCode) {
90  
91          if (!_ETAG_FILTER_ENABLED) {
92              return false;
93          }
94  
95          String eTag = Integer.toHexString(hashCode);
96  
97          response.setHeader(HttpHeaders.ETAG, eTag);
98  
99          String ifNoneMatch = request.getHeader(HttpHeaders.IF_NONE_MATCH);
100 
101         if (eTag.equals(ifNoneMatch)) {
102             response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
103             response.setContentLength(0);
104 
105             return true;
106         }
107         else {
108             return false;
109         }
110     }
111 
112     private static final boolean _ETAG_FILTER_ENABLED = GetterUtil.getBoolean(
113         PropsUtil.get(ETagFilter.class.getName()), true);
114 
115 }