001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018 package filters;
019
020
021 import java.io.IOException;
022
023 import javax.servlet.Filter;
024 import javax.servlet.FilterChain;
025 import javax.servlet.FilterConfig;
026 import javax.servlet.ServletException;
027 import javax.servlet.ServletRequest;
028 import javax.servlet.ServletResponse;
029
030
031 /**
032 * <p>Example filter that sets the character encoding to be used in parsing the
033 * incoming request, either unconditionally or only if the client did not
034 * specify a character encoding. Configuration of this filter is based on
035 * the following initialization parameters:</p>
036 * <ul>
037 * <li><strong>encoding</strong> - The character encoding to be configured
038 * for this request, either conditionally or unconditionally based on
039 * the <code>ignore</code> initialization parameter. This parameter
040 * is required, so there is no default.</li>
041 * <li><strong>ignore</strong> - If set to "true", any character encoding
042 * specified by the client is ignored, and the value returned by the
043 * <code>selectEncoding()</code> method is set. If set to "false,
044 * <code>selectEncoding()</code> is called <strong>only</strong> if the
045 * client has not already specified an encoding. By default, this
046 * parameter is set to "true".</li>
047 * </ul>
048 * <p/>
049 * <p>Although this filter can be used unchanged, it is also easy to
050 * subclass it and make the <code>selectEncoding()</code> method more
051 * intelligent about what encoding to choose, based on characteristics of
052 * the incoming request (such as the values of the <code>Accept-Language</code>
053 * and <code>User-Agent</code> headers, or a value stashed in the current
054 * user's session.</p>
055 *
056 * @author Craig McClanahan
057 * @version $Revision: 664175 $ $Date: 2008-06-06 18:43:44 -0400 (Fri, 06 Jun 2008) $
058 */
059
060 public class SetCharacterEncodingFilter implements Filter {
061
062 // ----------------------------------------------------- Instance Variables
063
064
065 /**
066 * The default character encoding to set for requests that pass through
067 * this filter.
068 */
069 protected String encoding = null;
070
071
072 /**
073 * The filter configuration object we are associated with. If this value
074 * is null, this filter instance is not currently configured.
075 */
076 protected FilterConfig filterConfig = null;
077
078
079 /**
080 * Should a character encoding specified by the client be ignored?
081 */
082 protected boolean ignore = true;
083
084 // --------------------------------------------------------- Public Methods
085
086
087 /**
088 * Take this filter out of service.
089 */
090 public void destroy() {
091
092 this.encoding = null;
093 this.filterConfig = null;
094
095 }
096
097
098 /**
099 * Select and set (if specified) the character encoding to be used to
100 * interpret request parameters for this request.
101 *
102 * @param request The servlet request we are processing
103 * @param result The servlet response we are creating
104 * @param chain The filter chain we are processing
105 * @throws IOException if an input/output error occurs
106 * @throws ServletException if a servlet error occurs
107 */
108 public void doFilter(ServletRequest request, ServletResponse response,
109 FilterChain chain)
110 throws IOException, ServletException {
111
112 // Conditionally select and set the character encoding to be used
113 if (ignore || (request.getCharacterEncoding() == null)) {
114 String encoding = selectEncoding(request);
115 if (encoding != null)
116 request.setCharacterEncoding(encoding);
117 }
118
119 // Pass control on to the next filter
120 chain.doFilter(request, response);
121
122 }
123
124
125 /**
126 * Place this filter into service.
127 *
128 * @param filterConfig The filter configuration object
129 */
130 public void init(FilterConfig filterConfig) throws ServletException {
131
132 this.filterConfig = filterConfig;
133 this.encoding = filterConfig.getInitParameter("encoding");
134 String value = filterConfig.getInitParameter("ignore");
135 if (value == null)
136 this.ignore = true;
137 else if (value.equalsIgnoreCase("true"))
138 this.ignore = true;
139 else if (value.equalsIgnoreCase("yes"))
140 this.ignore = true;
141 else
142 this.ignore = false;
143
144 }
145
146 // ------------------------------------------------------ Protected Methods
147
148
149 /**
150 * Select an appropriate character encoding to be used, based on the
151 * characteristics of the current request and/or filter initialization
152 * parameters. If no character encoding should be set, return
153 * <code>null</code>.
154 * <p/>
155 * The default implementation unconditionally returns the value configured
156 * by the <strong>encoding</strong> initialization parameter for this
157 * filter.
158 *
159 * @param request The servlet request we are processing
160 */
161 protected String selectEncoding(ServletRequest request) {
162
163 return (this.encoding);
164
165 }
166
167
168 }