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Tomcat example source code file (ExampleFilter.java)

This example Tomcat source code file (ExampleFilter.java) is included in the DevDaily.com "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 ExampleFilter.java 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
*
*     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 filters;


import java.io.IOException;
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();
	filterConfig.getServletContext().log
	    (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(");
	sb.append(filterConfig);
	sb.append(")");
	return (sb.toString());

    }


}

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