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Tomcat example source code file (

This example Tomcat source code file ( is included in the "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Tomcat tags/keywords

examplefilter, filter, filterchain, filterconfig, invokerfilter, invokerfilter, io, ioexception, servlet, servletexception, servletexception, servletresponse, string, string, stringbuffer, stringbuffer

The Tomcat source code

* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements.  See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.

package filters;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

 * Example filter that can be attached to either an individual servlet
 * or to a URL pattern.  This filter performs the following functions:
 * <ul>
 * <li>Attaches itself as a request attribute, under the attribute name
 *     defined by the value of the <code>attribute initialization
 *     parameter.</li>
 * <li>Calculates the number of milliseconds required to perform the
 *     servlet processing required by this request, including any
 *     subsequently defined filters, and logs the result to the servlet
 *     context log for this application.
 * </ul>
 * @author Craig McClanahan
 * @version $Revision: 500674 $ $Date: 2007-01-28 00:15:00 +0100 (dim., 28 janv. 2007) $

public final class ExampleFilter implements Filter {

    // ----------------------------------------------------- Instance Variables

     * The request attribute name under which we store a reference to ourself.
    private String attribute = null;

     * The filter configuration object we are associated with.  If this value
     * is null, this filter instance is not currently configured.
    private FilterConfig filterConfig = null;

    // --------------------------------------------------------- Public Methods

     * Take this filter out of service.
    public void destroy() {

        this.attribute = null;
        this.filterConfig = null;


     * Time the processing that is performed by all subsequent filters in the
     * current filter stack, including the ultimately invoked servlet.
     * @param request The servlet request we are processing
     * @param result The servlet response we are creating
     * @param chain The filter chain we are processing
     * @exception IOException if an input/output error occurs
     * @exception ServletException if a servlet error occurs
    public void doFilter(ServletRequest request, ServletResponse response,
                         FilterChain chain)
	throws IOException, ServletException {

	// Store ourselves as a request attribute (if requested)
	if (attribute != null)
	    request.setAttribute(attribute, this);

	// Time and log the subsequent processing
	long startTime = System.currentTimeMillis();
        chain.doFilter(request, response);
	long stopTime = System.currentTimeMillis();
	    (this.toString() + ": " + (stopTime - startTime) +
	     " milliseconds");


     * Place this filter into service.
     * @param filterConfig The filter configuration object
    public void init(FilterConfig filterConfig) throws ServletException {

	this.filterConfig = filterConfig;
        this.attribute = filterConfig.getInitParameter("attribute");


     * Return a String representation of this object.
    public String toString() {

	if (filterConfig == null)
	    return ("InvokerFilter()");
	StringBuffer sb = new StringBuffer("InvokerFilter(");
	return (sb.toString());



Other Tomcat examples (source code examples)

Here is a short list of links related to this Tomcat source code file:

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