001 /* 002 * Copyright 2004 The Apache Software Foundation 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * http://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017 package filters; 018 019 020 import java.io.IOException; 021 import javax.servlet.Filter; 022 import javax.servlet.FilterChain; 023 import javax.servlet.FilterConfig; 024 import javax.servlet.ServletException; 025 import javax.servlet.ServletRequest; 026 import javax.servlet.ServletResponse; 027 import javax.servlet.UnavailableException; 028 029 030 /** 031 * <p>Example filter that sets the character encoding to be used in parsing the 032 * incoming request, either unconditionally or only if the client did not 033 * specify a character encoding. Configuration of this filter is based on 034 * the following initialization parameters:</p> 035 * <ul> 036 * <li><strong>encoding</strong> - The character encoding to be configured 037 * for this request, either conditionally or unconditionally based on 038 * the <code>ignore</code> initialization parameter. This parameter 039 * is required, so there is no default.</li> 040 * <li><strong>ignore</strong> - If set to "true", any character encoding 041 * specified by the client is ignored, and the value returned by the 042 * <code>selectEncoding()</code> method is set. If set to "false, 043 * <code>selectEncoding()</code> is called <strong>only</strong> if the 044 * client has not already specified an encoding. By default, this 045 * parameter is set to "true".</li> 046 * </ul> 047 * 048 * <p>Although this filter can be used unchanged, it is also easy to 049 * subclass it and make the <code>selectEncoding()</code> method more 050 * intelligent about what encoding to choose, based on characteristics of 051 * the incoming request (such as the values of the <code>Accept-Language</code> 052 * and <code>User-Agent</code> headers, or a value stashed in the current 053 * user's session.</p> 054 * 055 * @author Craig McClanahan 056 * @version $Revision: 267129 $ $Date: 2004-03-18 08:40:35 -0800 (Thu, 18 Mar 2004) $ 057 */ 058 059 public class SetCharacterEncodingFilter implements Filter { 060 061 062 // ----------------------------------------------------- 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; 083 084 085 // --------------------------------------------------------- Public Methods 086 087 088 /** 089 * Take this filter out of service. 090 */ 091 public void destroy() { 092 093 this.encoding = null; 094 this.filterConfig = null; 095 096 } 097 098 099 /** 100 * Select and set (if specified) the character encoding to be used to 101 * interpret request parameters for this request. 102 * 103 * @param request The servlet request we are processing 104 * @param result The servlet response we are creating 105 * @param chain The filter chain we are processing 106 * 107 * @exception IOException if an input/output error occurs 108 * @exception ServletException if a servlet error occurs 109 */ 110 public void doFilter(ServletRequest request, ServletResponse response, 111 FilterChain chain) 112 throws IOException, ServletException { 113 114 // Conditionally select and set the character encoding to be used 115 if (ignore || (request.getCharacterEncoding() == null)) { 116 String encoding = selectEncoding(request); 117 if (encoding != null) 118 request.setCharacterEncoding(encoding); 119 } 120 121 // Pass control on to the next filter 122 chain.doFilter(request, response); 123 124 } 125 126 127 /** 128 * Place this filter into service. 129 * 130 * @param filterConfig The filter configuration object 131 */ 132 public void init(FilterConfig filterConfig) throws ServletException { 133 134 this.filterConfig = filterConfig; 135 this.encoding = filterConfig.getInitParameter("encoding"); 136 String value = filterConfig.getInitParameter("ignore"); 137 if (value == null) 138 this.ignore = true; 139 else if (value.equalsIgnoreCase("true")) 140 this.ignore = true; 141 else if (value.equalsIgnoreCase("yes")) 142 this.ignore = true; 143 else 144 this.ignore = false; 145 146 } 147 148 149 // ------------------------------------------------------ Protected Methods 150 151 152 /** 153 * Select an appropriate character encoding to be used, based on the 154 * characteristics of the current request and/or filter initialization 155 * parameters. If no character encoding should be set, return 156 * <code>null</code>. 157 * <p> 158 * The default implementation unconditionally returns the value configured 159 * by the <strong>encoding</strong> initialization parameter for this 160 * filter. 161 * 162 * @param request The servlet request we are processing 163 */ 164 protected String selectEncoding(ServletRequest request) { 165 166 return (this.encoding); 167 168 } 169 170 171 }