1
2
3 /*
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
5 *
6 * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
7 *
8 * Portions Copyright Apache Software Foundation.
9 *
10 * The contents of this file are subject to the terms of either the GNU
11 * General Public License Version 2 only ("GPL") or the Common Development
12 * and Distribution License("CDDL") (collectively, the "License"). You
13 * may not use this file except in compliance with the License. You can obtain
14 * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
15 * or glassfish/bootstrap/legal/LICENSE.txt. See the License for the specific
16 * language governing permissions and limitations under the License.
17 *
18 * When distributing the software, include this License Header Notice in each
19 * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
20 * Sun designates this particular file as subject to the "Classpath" exception
21 * as provided by Sun in the GPL Version 2 section of the License file that
22 * accompanied this code. If applicable, add the following below the License
23 * Header, with the fields enclosed by brackets [] replaced by your own
24 * identifying information: "Portions Copyrighted [year]
25 * [name of copyright owner]"
26 *
27 * Contributor(s):
28 *
29 * If you wish your version of this file to be governed by only the CDDL or
30 * only the GPL Version 2, indicate your decision by adding "[Contributor]
31 * elects to include this software in this distribution under the [CDDL or GPL
32 * Version 2] license." If you don't indicate a single choice of license, a
33 * recipient has the option to distribute your version of this file under
34 * either the CDDL, the GPL Version 2 or to extend the choice of license to
35 * its licensees as provided above. However, if you add GPL Version 2 code
36 * and therefore, elected the GPL Version 2 license, then the option applies
37 * only if the new code is made subject to such option by the copyright
38 * holder.
39 */
40
41 package javax.servlet;
42
43 import java.io.IOException;
44
45 /**
46 * A filter is an object that performs filtering tasks on either the request to a resource (a servlet or static content), or on the response from a resource, or both.
47 * <br><br>
48 * Filters perform filtering in the <code>doFilter</code> method. Every Filter has access to
49 ** a FilterConfig object from which it can obtain its initialization parameters, a
50 ** reference to the ServletContext which it can use, for example, to load resources
51 ** needed for filtering tasks.
52 ** <p>
53 ** Filters are configured in the deployment descriptor of a web application
54 ** <p>
55 ** Examples that have been identified for this design are<br>
56 ** 1) Authentication Filters <br>
57 ** 2) Logging and Auditing Filters <br>
58 ** 3) Image conversion Filters <br>
59 ** 4) Data compression Filters <br>
60 ** 5) Encryption Filters <br>
61 ** 6) Tokenizing Filters <br>
62 ** 7) Filters that trigger resource access events <br>
63 ** 8) XSL/T filters <br>
64 ** 9) Mime-type chain Filter <br>
65 * @since Servlet 2.3
66 */
67
68 public interface Filter {
69
70 /**
71 * Called by the web container to indicate to a filter that it is being placed into
72 * service. The servlet container calls the init method exactly once after instantiating the
73 * filter. The init method must complete successfully before the filter is asked to do any
74 * filtering work. <br><br>
75
76 * The web container cannot place the filter into service if the init method either<br>
77 * 1.Throws a ServletException <br>
78 * 2.Does not return within a time period defined by the web container
79 */
80 public void init(FilterConfig filterConfig) throws ServletException;
81
82
83 /**
84 * The <code>doFilter</code> method of the Filter is called by the container
85 * each time a request/response pair is passed through the chain due
86 * to a client request for a resource at the end of the chain. The FilterChain passed in to this
87 * method allows the Filter to pass on the request and response to the next entity in the
88 * chain.<p>
89 * A typical implementation of this method would follow the following pattern:- <br>
90 * 1. Examine the request<br>
91 * 2. Optionally wrap the request object with a custom implementation to
92 * filter content or headers for input filtering <br>
93 * 3. Optionally wrap the response object with a custom implementation to
94 * filter content or headers for output filtering <br>
95 * 4. a) <strong>Either</strong> invoke the next entity in the chain using the FilterChain object (<code>chain.doFilter()</code>), <br>
96 ** 4. b) <strong>or</strong> not pass on the request/response pair to the next entity in the filter chain to block the request processing<br>
97 ** 5. Directly set headers on the response after invocation of the next entity in the filter chain.
98 **/
99 public void doFilter ( ServletRequest request, ServletResponse response, FilterChain chain ) throws IOException, ServletException;
100
101 /**
102 * Called by the web container to indicate to a filter that it is being taken out of service. This
103 * method is only called once all threads within the filter's doFilter method have exited or after
104 * a timeout period has passed. After the web container calls this method, it will not call the
105 * doFilter method again on this instance of the filter. <br><br>
106 *
107 * This method gives the filter an opportunity to clean up any resources that are being held (for
108 * example, memory, file handles, threads) and make sure that any persistent state is synchronized
109 * with the filter's current state in memory.
110 */
111
112 public void destroy();
113
114
115 }
116
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