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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

filter, filter, filterchain, filterconfig, filterconfig, io, ioexception, servlet, servletexception, servletexception, servletresponse, setcharacterencodingfilter, string, string

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;

 * <p>Example filter that sets the character encoding to be used in parsing the
 * incoming request, either unconditionally or only if the client did not
 * specify a character encoding.  Configuration of this filter is based on
 * the following initialization parameters:</p>
 * <ul>
 * <li>encoding - The character encoding to be configured
 *     for this request, either conditionally or unconditionally based on
 *     the <code>ignore initialization parameter.  This parameter
 *     is required, so there is no default.</li>
 * <li>ignore - If set to "true", any character encoding
 *     specified by the client is ignored, and the value returned by the
 *     <code>selectEncoding() method is set.  If set to "false,
 *     <code>selectEncoding() is called only if the
 *     client has not already specified an encoding.  By default, this
 *     parameter is set to "true".</li>
 * </ul>
 * <p>Although this filter can be used unchanged, it is also easy to
 * subclass it and make the <code>selectEncoding() method more
 * intelligent about what encoding to choose, based on characteristics of
 * the incoming request (such as the values of the <code>Accept-Language
 * and <code>User-Agent headers, or a value stashed in the current
 * user's session.</p>
 * @author Craig McClanahan
 * @version $Revision: 500674 $ $Date: 2007-01-28 00:15:00 +0100 (dim., 28 janv. 2007) $

public class SetCharacterEncodingFilter implements Filter {

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

     * The default character encoding to set for requests that pass through
     * this filter.
    protected String encoding = null;

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

     * Should a character encoding specified by the client be ignored?
    protected boolean ignore = true;

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

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

        this.encoding = null;
        this.filterConfig = null;


     * Select and set (if specified) the character encoding to be used to
     * interpret request parameters for this request.
     * @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 {

        // Conditionally select and set the character encoding to be used
        if (ignore || (request.getCharacterEncoding() == null)) {
            String encoding = selectEncoding(request);
            if (encoding != null)

	// Pass control on to the next filter
        chain.doFilter(request, response);


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

	this.filterConfig = filterConfig;
        this.encoding = filterConfig.getInitParameter("encoding");
        String value = filterConfig.getInitParameter("ignore");
        if (value == null)
            this.ignore = true;
        else if (value.equalsIgnoreCase("true"))
            this.ignore = true;
        else if (value.equalsIgnoreCase("yes"))
            this.ignore = true;
            this.ignore = false;


    // ------------------------------------------------------ Protected Methods

     * Select an appropriate character encoding to be used, based on the
     * characteristics of the current request and/or filter initialization
     * parameters.  If no character encoding should be set, return
     * <code>null.
     * <p>
     * The default implementation unconditionally returns the value configured
     * by the <strong>encoding initialization parameter for this
     * filter.
     * @param request The servlet request we are processing
    protected String selectEncoding(ServletRequest request) {

        return (this.encoding);



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