1 2 3 /* 4 * The contents of this file are subject to the terms 5 * of the Common Development and Distribution License 6 * (the "License"). You may not use this file except 7 * in compliance with the License. 8 * 9 * You can obtain a copy of the license at 10 * glassfish/bootstrap/legal/CDDLv1.0.txt or 11 * https://glassfish.dev.java.net/public/CDDLv1.0.html. 12 * See the License for the specific language governing 13 * permissions and limitations under the License. 14 * 15 * When distributing Covered Code, include this CDDL 16 * HEADER in each file and include the License file at 17 * glassfish/bootstrap/legal/CDDLv1.0.txt. If applicable, 18 * add the following below this CDDL HEADER, with the 19 * fields enclosed by brackets "[]" replaced with your 20 * own identifying information: Portions Copyright [yyyy] 21 * [name of copyright owner] 22 * 23 * Copyright 2005 Sun Microsystems, Inc. All rights reserved. 24 * 25 * Portions Copyright Apache Software Foundation. 26 */ 27 28 package javax.servlet; 29 30 import java.io.IOException; 31 32 /** 33 * 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. 34 * <br><br> 35 * Filters perform filtering in the <code>doFilter</code> method. Every Filter has access to 36 ** a FilterConfig object from which it can obtain its initialization parameters, a 37 ** reference to the ServletContext which it can use, for example, to load resources 38 ** needed for filtering tasks. 39 ** <p> 40 ** Filters are configured in the deployment descriptor of a web application 41 ** <p> 42 ** Examples that have been identified for this design are<br> 43 ** 1) Authentication Filters <br> 44 ** 2) Logging and Auditing Filters <br> 45 ** 3) Image conversion Filters <br> 46 ** 4) Data compression Filters <br> 47 ** 5) Encryption Filters <br> 48 ** 6) Tokenizing Filters <br> 49 ** 7) Filters that trigger resource access events <br> 50 ** 8) XSL/T filters <br> 51 ** 9) Mime-type chain Filter <br> 52 * @since Servlet 2.3 53 */ 54 55 public interface Filter { 56 57 /** 58 * Called by the web container to indicate to a filter that it is being placed into 59 * service. The servlet container calls the init method exactly once after instantiating the 60 * filter. The init method must complete successfully before the filter is asked to do any 61 * filtering work. <br><br> 62 63 * The web container cannot place the filter into service if the init method either<br> 64 * 1.Throws a ServletException <br> 65 * 2.Does not return within a time period defined by the web container 66 */ 67 public void init(FilterConfig filterConfig) throws ServletException; 68 69 70 /** 71 * The <code>doFilter</code> method of the Filter is called by the container 72 * each time a request/response pair is passed through the chain due 73 * to a client request for a resource at the end of the chain. The FilterChain passed in to this 74 * method allows the Filter to pass on the request and response to the next entity in the 75 * chain.<p> 76 * A typical implementation of this method would follow the following pattern:- <br> 77 * 1. Examine the request<br> 78 * 2. Optionally wrap the request object with a custom implementation to 79 * filter content or headers for input filtering <br> 80 * 3. Optionally wrap the response object with a custom implementation to 81 * filter content or headers for output filtering <br> 82 * 4. a) <strong>Either</strong> invoke the next entity in the chain using the FilterChain object (<code>chain.doFilter()</code>), <br> 83 ** 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> 84 ** 5. Directly set headers on the response after invocation of the next entity in the filter chain. 85 **/ 86 public void doFilter ( ServletRequest request, ServletResponse response, FilterChain chain ) throws IOException, ServletException; 87 88 /** 89 * Called by the web container to indicate to a filter that it is being taken out of service. This 90 * method is only called once all threads within the filter's doFilter method have exited or after 91 * a timeout period has passed. After the web container calls this method, it will not call the 92 * doFilter method again on this instance of the filter. <br><br> 93 * 94 * This method gives the filter an opportunity to clean up any resources that are being held (for 95 * example, memory, file handles, threads) and make sure that any persistent state is synchronized 96 * with the filter's current state in memory. 97 */ 98 99 public void destroy(); 100 101 102 } 103