View Javadoc

    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