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1   /*
2    * Copyright 2010 University Corporation for Advanced Internet Development, Inc.
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    * http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  
17  package edu.internet2.middleware.shibboleth.idp.util;
18  
19  import java.io.IOException;
20  
21  import javax.servlet.Filter;
22  import javax.servlet.FilterChain;
23  import javax.servlet.FilterConfig;
24  import javax.servlet.ServletException;
25  import javax.servlet.ServletRequest;
26  import javax.servlet.ServletResponse;
27  import javax.servlet.http.HttpServletResponse;
28  
29  /**
30   * An HTTP filter that adds the following headers/values to the {@link HttpServletResponse} and thus, hopefully,
31   * prevents caching of the response on all browser.
32   * <ul>
33   * <li>Expires: 0</li>
34   * <li>Cache-Control: no-cache, no-store, must-revalidate, max-age=0
35   * <li>
36   * <li>Pragma: no-cache</li>
37   * </ul>
38   */
39  public class NoCacheFilter implements Filter {
40  
41      /** {@inheritDoc} */
42      public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException,
43              ServletException {
44          HttpServletResponse httpResponse = (HttpServletResponse) response;
45  
46          httpResponse.setHeader("Expires", "0");
47          httpResponse.setHeader("Cache-Control", "no-cache, no-store, must-revalidate, max-age=0");
48          httpResponse.setHeader("Pragma", "no-cache");
49          chain.doFilter(request, response);
50      }
51  
52      /** {@inheritDoc} */
53      public void init(FilterConfig filterConfig) throws ServletException {
54          // nothing to do here
55      }
56  
57      /** {@inheritDoc} */
58      public void destroy() {
59          // nothing to do here
60      }
61  }