https://projects.eclipse.org/projects/ee4j.servlet: Provides, via submodules, a base configuration for JBoss project builds, as well as a derived configuration supporting multi-release JARs (JBoss by Red Hat)
  • Ed Burns
  • Shing Wai Chan 
/*
 * Copyright (c) 1997, 2018 Oracle and/or its affiliates and others.
 * All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package javax.servlet.http;

import java.io.IOException;
import javax.servlet.FilterChain;
import javax.servlet.GenericFilter;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;



Provides an abstract class to be subclassed to create an HTTP filter suitable for a Web site. A subclass of
HttpFilter should override doFilter(HttpServletRequest, HttpServletResponse, FilterChain). 



Filters typically run on multithreaded servers, so be aware that a filter must handle concurrent requests and be
careful to synchronize access to shared resources. Shared resources include in-memory data such as instance or class
variables and external objects such as files, database connections, and network connections. See the
 Java Tutorial on Multithreaded
Programming for more information on handling multiple threads in a Java program.

Author:Various
Since:Servlet 4.0
/**
 *
 * <p>
 * Provides an abstract class to be subclassed to create an HTTP filter suitable for a Web site. A subclass of
 * <code>HttpFilter</code> should override
 * {@link #doFilter(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse, javax.servlet.FilterChain) }.
 * </p>
 *
 * <p>
 * Filters typically run on multithreaded servers, so be aware that a filter must handle concurrent requests and be
 * careful to synchronize access to shared resources. Shared resources include in-memory data such as instance or class
 * variables and external objects such as files, database connections, and network connections. See the
 * <a href="https://docs.oracle.com/javase/tutorial/essential/concurrency/"> Java Tutorial on Multithreaded
 * Programming</a> for more information on handling multiple threads in a Java program.
 *
 * @author Various
 *
 * @since Servlet 4.0
 */
public abstract class HttpFilter extends GenericFilter {

    private static final long serialVersionUID = 7478463438252262094L;

    

Does nothing, because this is an abstract class.



Since:4.0
/**
     * <p>
     * Does nothing, because this is an abstract class.
     * </p>
     * 
     * @since 4.0
     */
    public HttpFilter() {
    }

    

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. There's
no need to override this method.



 The default implementation inspects the incoming req and res objects to determine if they are instances of HttpServletRequest and HttpServletResponse, respectively. If not, a ServletException is thrown. Otherwise, the protected doFilter(HttpServletRequest, HttpServletResponse, FilterChain) method is called. 


Params:
  • req –  a ServletRequest object that contains the request the client has made of the filter
  • res –  a ServletResponse object that contains the response the filter sends to the client
  • chain – the FilterChain for invoking the next filter or the resource
Throws:
Since:Servlet 4.0
/**
     *
     * <p>
     * The <code>doFilter</code> 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. There's
     * no need to override this method.
     * </p>
     * 
     * <p>
     * The default implementation inspects the incoming {@code req} and {@code res} objects to determine if they are
     * instances of {@link HttpServletRequest} and {@link HttpServletResponse}, respectively. If not, a
     * {@link ServletException} is thrown. Otherwise, the protected
     * {@link #doFilter(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse, javax.servlet.FilterChain)}
     * method is called.
     * </p>
     *
     * @param req   a {@link ServletRequest} object that contains the request the client has made of the filter
     *
     * @param res   a {@link ServletResponse} object that contains the response the filter sends to the client
     * 
     * @param chain the <code>FilterChain</code> for invoking the next filter or the resource
     * 
     * @throws IOException      if an input or output error is detected when the filter handles the request
     *
     * @throws ServletException if the request for the could not be handled or either parameter is not an instance of
     *                          the respective {@link HttpServletRequest} or {@link HttpServletResponse}.
     *
     * @since Servlet 4.0
     */
    @Override
    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
            throws IOException, ServletException {
        if (!(req instanceof HttpServletRequest && res instanceof HttpServletResponse)) {
            throw new ServletException("non-HTTP request or response");
        }

        this.doFilter((HttpServletRequest) req, (HttpServletResponse) res, chain);
    }

    

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.



 The default implementation simply calls FilterChain.doFilter 


Params:
  • req –  a HttpServletRequest object that contains the request the client has made of the filter
  • res –  a HttpServletResponse object that contains the response the filter sends to the client
  • chain – the FilterChain for invoking the next filter or the resource
Throws:
  • IOException –      if an input or output error is detected when the filter handles the request
  • ServletException – if the request for the could not be handled
Since:Servlet 4.0
/**
     *
     * <p>
     * The <code>doFilter</code> 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.
     * </p>
     * 
     * <p>
     * The default implementation simply calls {@link FilterChain#doFilter}
     * </p>
     *
     * @param req   a {@link HttpServletRequest} object that contains the request the client has made of the filter
     *
     * @param res   a {@link HttpServletResponse} object that contains the response the filter sends to the client
     * 
     * @param chain the <code>FilterChain</code> for invoking the next filter or the resource
     * 
     * @throws IOException      if an input or output error is detected when the filter handles the request
     *
     * @throws ServletException if the request for the could not be handled
     *
     * @since Servlet 4.0
     */
    protected void doFilter(HttpServletRequest req, HttpServletResponse res, FilterChain chain)
            throws IOException, ServletException {
        chain.doFilter(req, res);
    }

}