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1   package org.apache.turbine.util;
2   
3   /*
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *   http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing,
15   * software distributed under the License is distributed on an
16   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17   * KIND, either express or implied.  See the License for the
18   * specific language governing permissions and limitations
19   * under the License.
20   */
21  
22  import java.text.SimpleDateFormat;
23  import java.util.Date;
24  import java.util.Locale;
25  import java.util.TimeZone;
26  
27  /**
28   * This class provides utilities for handling some semi-trivial HTTP stuff that
29   * would otherwise be handled elsewhere.
30   *
31   * @author <a href="mailto:magnus@handpoint.com">Magnús Þór Torfason</a>
32   * @version $Id: HttpUtils.java 1071052 2011-02-15 20:54:47Z tv $
33   */
34  public class HttpUtils
35  {
36      /**
37       * The date format to use for HTTP Dates.
38       */
39      private static SimpleDateFormat httpDateFormat;
40  
41      static
42      {
43          httpDateFormat = new SimpleDateFormat(
44                  "EEE, dd MMM yyyy HH:mm:ss z", Locale.US);
45          httpDateFormat.setTimeZone(TimeZone.getTimeZone("GMT"));
46      }
47  
48      /**
49       * Formats a java Date according to rfc 1123, the rfc standard for dates in
50       * http.
51       *
52       * @param date The Date to format
53       * @return A String representation of the date
54       */
55      public static String formatHttpDate(Date date)
56      {
57          synchronized (httpDateFormat)
58          {
59              return httpDateFormat.format(date);
60          }
61      }
62  
63      /**
64       * This method sets the required expiration headers in the response for a
65       * given RunData object.  This method attempts to set all relevant headers,
66       * both for HTTP 1.0 and HTTP 1.1.
67       *
68       * @param data The RunData object we are setting cache information for.
69       * @param expiry The number of milliseconds until the document should expire,
70       * <code>0</code> indicating immediate expiration (i.e. no caching).
71       */
72      public static void setCacheHeaders(RunData data, int expiry)
73      {
74          if (0 == expiry)
75          {
76              data.getResponse().setHeader("Pragma", "no-cache");
77              data.getResponse().setHeader("Cache-Control", "no-cache");
78              data.getResponse().setDateHeader("Expires", System.currentTimeMillis());
79          }
80          else
81          {
82              data.getResponse().setDateHeader("Expires", System.currentTimeMillis() + expiry);
83          }
84      }
85  }