All Downloads are FREE. Search and download functionalities are using the official Maven repository.

javax.servlet.Filter Maven / Gradle / Ivy

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright (c) 1997-2010 Oracle and/or its affiliates. All rights reserved.
 *
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License.  You can
 * obtain a copy of the License at
 * https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html
 * or packager/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 *
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at packager/legal/LICENSE.txt.
 *
 * GPL Classpath Exception:
 * Oracle designates this particular file as subject to the "Classpath"
 * exception as provided by Oracle in the GPL Version 2 section of the License
 * file that accompanied this code.
 *
 * Modifications:
 * If applicable, add the following below the License Header, with the fields
 * enclosed by brackets [] replaced by your own identifying information:
 * "Portions Copyright [year] [name of copyright owner]"
 *
 * Contributor(s):
 * If you wish your version of this file to be governed by only the CDDL or
 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
 * only if the new code is made subject to such option by the copyright
 * holder.
 *
 *
 * This file incorporates work covered by the following copyright and
 * permission notice:
 *
 * Copyright 2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package javax.servlet;

import java.io.IOException;

/**
 * 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.
 * 
 * 

Filters perform filtering in the doFilter method. * Every Filter has access to a FilterConfig object from which it can obtain * its initialization parameters, and a reference to the ServletContext which * it can use, for example, to load resources needed for filtering tasks. * *

Filters are configured in the deployment descriptor of a web * application. * *

Examples that have been identified for this design are: *

    *
  1. Authentication Filters *
  2. Logging and Auditing Filters *
  3. Image conversion Filters *
  4. Data compression Filters *
  5. Encryption Filters *
  6. Tokenizing Filters *
  7. Filters that trigger resource access events *
  8. XSL/T filters *
  9. Mime-type chain Filter *
* * @since Servlet 2.3 */ public interface Filter { /** * Called by the web container to indicate to a filter that it is * being placed into service. * *

The servlet container calls the init * method exactly once after instantiating the filter. The init * method must complete successfully before the filter is asked to do any * filtering work. * *

The web container cannot place the filter into service if the init * method either *

    *
  1. Throws a ServletException *
  2. Does not return within a time period defined by the web container *
*/ public void init(FilterConfig filterConfig) throws ServletException; /** * The doFilter method of the Filter is called by the * container each time a request/response pair is passed through the * chain due to a client request for a resource at the end of the chain. * The FilterChain passed in to this method allows the Filter to pass * on the request and response to the next entity in the chain. * *

A typical implementation of this method would follow the following * pattern: *

    *
  1. Examine the request *
  2. Optionally wrap the request object with a custom implementation to * filter content or headers for input filtering *
  3. Optionally wrap the response object with a custom implementation to * filter content or headers for output filtering *
  4. *
      *
    • Either invoke the next entity in the chain * using the FilterChain object * (chain.doFilter()), *
    • or not pass on the request/response pair to * the next entity in the filter chain to * block the request processing *
    *
  5. Directly set headers on the response after invocation of the * next entity in the filter chain. *
*/ public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException; /** * Called by the web container to indicate to a filter that it is being * taken out of service. * *

This method is only called once all threads within the filter's * doFilter method have exited or after a timeout period has passed. * After the web container calls this method, it will not call the * doFilter method again on this instance of the filter. * *

This method gives the filter an opportunity to clean up any * resources that are being held (for example, memory, file handles, * threads) and make sure that any persistent state is synchronized * with the filter's current state in memory. */ public void destroy(); }





© 2015 - 2024 Weber Informatics LLC | Privacy Policy