javax.servlet.Filter Maven / Gradle / Ivy
/*
* The contents of this file are subject to the terms
* of the Common Development and Distribution License
* (the "License"). You may not use this file except
* in compliance with the License.
*
* You can obtain a copy of the license at
* glassfish/bootstrap/legal/CDDLv1.0.txt or
* https://glassfish.dev.java.net/public/CDDLv1.0.html.
* See the License for the specific language governing
* permissions and limitations under the License.
*
* When distributing Covered Code, include this CDDL
* HEADER in each file and include the License file at
* glassfish/bootstrap/legal/CDDLv1.0.txt. If applicable,
* add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your
* own identifying information: Portions Copyright [yyyy]
* [name of copyright owner]
*
* Copyright 2005 Sun Microsystems, Inc. All rights reserved.
*
* Portions Copyright Apache Software Foundation.
*/
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, 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. a) Either invoke the next entity in the chain using the FilterChain object (chain.doFilter()),
** 4. b) 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();
}