1 /*
   2 * Copyright 2004 The Apache Software Foundation
   3 *
   4 * Licensed under the Apache License, Version 2.0 (the "License");
   5 * you may not use this file except in compliance with the License.
   6 * You may obtain a copy of the License at
   7 *
   8 *     http://www.apache.org/licenses/LICENSE-2.0
   9 *
  10 * Unless required by applicable law or agreed to in writing, software
  11 * distributed under the License is distributed on an "AS IS" BASIS,
  12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13 * See the License for the specific language governing permissions and
  14 * limitations under the License.
  15 */
  16 
  17 package org.apache.servlet;
  18 
  19 import java.io.IOException;
  20 
  21 import javax.servlet.Filter;
  22 import javax.servlet.FilterChain;
  23 import javax.servlet.FilterConfig;
  24 import javax.servlet.ServletException;
  25 import javax.servlet.ServletRequest;
  26 import javax.servlet.ServletResponse;
  27 
  28 /**
  29  * <p>Example filter that sets the character encoding to be used in parsing the
  30  * incoming request, either unconditionally or only if the client did not
  31  * specify a character encoding.  Configuration of this filter is based on
  32  * the following initialization parameters:</p>
  33  * <ul>
  34  * <li><strong>encoding</strong> - The character encoding to be configured
  35  *     for this request, either conditionally or unconditionally based on
  36  *     the <code>ignore</code> initialization parameter.  This parameter
  37  *     is required, so there is no default.</li>
  38  * <li><strong>ignore</strong> - If set to "true", any character encoding
  39  *     specified by the client is ignored, and the value returned by the
  40  *     <code>selectEncoding()</code> method is set.  If set to "false,
  41  *     <code>selectEncoding()</code> is called <strong>only</strong> if the
  42  *     client has not already specified an encoding.  By default, this
  43  *     parameter is set to "true".</li>
  44  * </ul>
  45  *
  46  * <p>Although this filter can be used unchanged, it is also easy to
  47  * subclass it and make the <code>selectEncoding()</code> method more
  48  * intelligent about what encoding to choose, based on characteristics of
  49  * the incoming request (such as the values of the <code>Accept-Language</code>
  50  * and <code>User-Agent</code> headers, or a value stashed in the current
  51  * user's session.</p>
  52  *
  53  * @author Craig McClanahan
  54  * @version $Revision: 267129 $ $Date: 2004-03-18 11:40:35 -0500 (Thu, 18 Mar 2004) $
  55  */
  56 
  57 public class SetCharacterEncodingFilter implements Filter {
  58 
  59     // ----------------------------------------------------- Instance Variables
  60 
  61     /**
  62      * The default character encoding to set for requests that pass through
  63      * this filter.
  64      */
  65     protected String encoding = null;
  66 
  67     /**
  68      * The filter configuration object we are associated with.  If this value
  69      * is null, this filter instance is not currently configured.
  70      */
  71     protected FilterConfig filterConfig = null;
  72 
  73     /**
  74      * Should a character encoding specified by the client be ignored?
  75      */
  76     protected boolean ignore = true;
  77 
  78     // --------------------------------------------------------- Public Methods
  79 
  80     /**
  81      * Take this filter out of service.
  82      */
  83     public void destroy() {
  84 
  85         this.encoding = null;
  86         this.filterConfig = null;
  87 
  88     }
  89 
  90     /**
  91      * Select and set (if specified) the character encoding to be used to
  92      * interpret request parameters for this request.
  93      *
  94      * @param request The servlet request we are processing
  95      * @param result The servlet response we are creating
  96      * @param chain The filter chain we are processing
  97      *
  98      * @exception IOException if an input/output error occurs
  99      * @exception ServletException if a servlet error occurs
 100      */
 101     public void doFilter(ServletRequest request, ServletResponse response,
 102                          FilterChain chain)
 103     throws IOException, ServletException {
 104 
 105         // Conditionally select and set the character encoding to be used
 106         if (ignore || (request.getCharacterEncoding() == null)) {
 107             String encoding = selectEncoding(request);
 108             if (encoding != null)
 109                 request.setCharacterEncoding(encoding);
 110         }
 111 
 112         // Pass control on to the next filter
 113         chain.doFilter(request, response);
 114 
 115     }
 116 
 117     /**
 118      * Place this filter into service.
 119      *
 120      * @param filterConfig The filter configuration object
 121      */
 122     public void init(FilterConfig filterConfig) throws ServletException {
 123 
 124         this.filterConfig = filterConfig;
 125         this.encoding = filterConfig.getInitParameter("encoding");
 126         String value = filterConfig.getInitParameter("ignore");
 127         if (value == null)
 128             this.ignore = true;
 129         else if (value.equalsIgnoreCase("true"))
 130             this.ignore = true;
 131         else if (value.equalsIgnoreCase("yes"))
 132             this.ignore = true;
 133         else
 134             this.ignore = false;
 135 
 136     }
 137 
 138     // ------------------------------------------------------ Protected Methods
 139 
 140     /**
 141      * Select an appropriate character encoding to be used, based on the
 142      * characteristics of the current request and/or filter initialization
 143      * parameters.  If no character encoding should be set, return
 144      * <code>null</code>.
 145      * <p>
 146      * The default implementation unconditionally returns the value configured
 147      * by the <strong>encoding</strong> initialization parameter for this
 148      * filter.
 149      *
 150      * @param request The servlet request we are processing
 151      */
 152     protected String selectEncoding(ServletRequest request) {
 153 
 154         return (this.encoding);
 155 
 156     }
 157 }

SetCharacterEncodingFilter (last edited 2009-09-20 23:40:53 by localhost)