1 | /* |
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2 | * Licensed to the Apache Software Foundation (ASF) under one or more |
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3 | * contributor license agreements. See the NOTICE file distributed with |
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4 | * this work for additional information regarding copyright ownership. |
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5 | * The ASF licenses this file to You under the Apache License, Version 2.0 |
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6 | * (the "License"); you may not use this file except in compliance with |
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7 | * the License. You may obtain a copy of the License at |
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8 | * |
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9 | * http://www.apache.org/licenses/LICENSE-2.0 |
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10 | * |
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11 | * Unless required by applicable law or agreed to in writing, software |
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12 | * distributed under the License is distributed on an "AS IS" BASIS, |
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13 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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14 | * See the License for the specific language governing permissions and |
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15 | * limitations under the License. |
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16 | */ |
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17 | |
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18 | package filters; |
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19 | |
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20 | |
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21 | import java.io.IOException; |
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22 | import javax.servlet.Filter; |
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23 | import javax.servlet.FilterChain; |
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24 | import javax.servlet.FilterConfig; |
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25 | import javax.servlet.ServletException; |
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26 | import javax.servlet.ServletRequest; |
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27 | import javax.servlet.ServletResponse; |
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28 | |
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29 | |
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30 | /** |
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31 | * <p>Example filter that sets the character encoding to be used in parsing the |
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32 | * incoming request, either unconditionally or only if the client did not |
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33 | * specify a character encoding. Configuration of this filter is based on |
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34 | * the following initialization parameters:</p> |
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35 | * <ul> |
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36 | * <li><strong>encoding</strong> - The character encoding to be configured |
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37 | * for this request, either conditionally or unconditionally based on |
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38 | * the <code>ignore</code> initialization parameter. This parameter |
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39 | * is required, so there is no default.</li> |
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40 | * <li><strong>ignore</strong> - If set to "true", any character encoding |
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41 | * specified by the client is ignored, and the value returned by the |
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42 | * <code>selectEncoding()</code> method is set. If set to "false, |
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43 | * <code>selectEncoding()</code> is called <strong>only</strong> if the |
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44 | * client has not already specified an encoding. By default, this |
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45 | * parameter is set to "true".</li> |
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46 | * </ul> |
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47 | * |
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48 | * <p>Although this filter can be used unchanged, it is also easy to |
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49 | * subclass it and make the <code>selectEncoding()</code> method more |
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50 | * intelligent about what encoding to choose, based on characteristics of |
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51 | * the incoming request (such as the values of the <code>Accept-Language</code> |
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52 | * and <code>User-Agent</code> headers, or a value stashed in the current |
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53 | * user's session.</p> |
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54 | * |
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55 | * @author Craig McClanahan |
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56 | * @version $Revision: 500674 $ $Date: 2007-01-28 00:15:00 +0100 (Sun, 28 Jan 2007) $ |
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57 | */ |
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58 | |
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59 | public class SetCharacterEncodingFilter implements Filter { |
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60 | |
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61 | |
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62 | // ----------------------------------------------------- Instance Variables |
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63 | |
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64 | |
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65 | /** |
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66 | * The default character encoding to set for requests that pass through |
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67 | * this filter. |
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68 | */ |
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69 | protected String encoding = null; |
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70 | |
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71 | |
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72 | /** |
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73 | * The filter configuration object we are associated with. If this value |
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74 | * is null, this filter instance is not currently configured. |
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75 | */ |
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76 | protected FilterConfig filterConfig = null; |
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77 | |
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78 | |
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79 | /** |
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80 | * Should a character encoding specified by the client be ignored? |
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81 | */ |
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82 | protected boolean ignore = true; |
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83 | |
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84 | |
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85 | // --------------------------------------------------------- Public Methods |
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86 | |
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87 | |
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88 | /** |
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89 | * Take this filter out of service. |
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90 | */ |
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91 | public void destroy() { |
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92 | |
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93 | this.encoding = null; |
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94 | this.filterConfig = null; |
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95 | |
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96 | } |
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97 | |
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98 | |
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99 | /** |
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100 | * Select and set (if specified) the character encoding to be used to |
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101 | * interpret request parameters for this request. |
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102 | * |
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103 | * @param request The servlet request we are processing |
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104 | * @param result The servlet response we are creating |
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105 | * @param chain The filter chain we are processing |
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106 | * |
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107 | * @exception IOException if an input/output error occurs |
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108 | * @exception ServletException if a servlet error occurs |
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109 | */ |
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110 | public void doFilter(ServletRequest request, ServletResponse response, |
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111 | FilterChain chain) |
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112 | throws IOException, ServletException { |
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113 | |
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114 | // Conditionally select and set the character encoding to be used |
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115 | if (ignore || (request.getCharacterEncoding() == null)) { |
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116 | String encoding = selectEncoding(request); |
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117 | if (encoding != null) |
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118 | request.setCharacterEncoding(encoding); |
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119 | } |
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120 | |
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121 | // Pass control on to the next filter |
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122 | chain.doFilter(request, response); |
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123 | |
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124 | } |
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125 | |
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126 | |
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127 | /** |
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128 | * Place this filter into service. |
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129 | * |
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130 | * @param filterConfig The filter configuration object |
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131 | */ |
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132 | public void init(FilterConfig filterConfig) throws ServletException { |
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133 | |
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134 | this.filterConfig = filterConfig; |
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135 | this.encoding = filterConfig.getInitParameter("encoding"); |
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136 | String value = filterConfig.getInitParameter("ignore"); |
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137 | if (value == null) |
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138 | this.ignore = true; |
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139 | else if (value.equalsIgnoreCase("true")) |
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140 | this.ignore = true; |
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141 | else if (value.equalsIgnoreCase("yes")) |
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142 | this.ignore = true; |
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143 | else |
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144 | this.ignore = false; |
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145 | |
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146 | } |
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147 | |
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148 | |
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149 | // ------------------------------------------------------ Protected Methods |
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150 | |
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151 | |
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152 | /** |
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153 | * Select an appropriate character encoding to be used, based on the |
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154 | * characteristics of the current request and/or filter initialization |
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155 | * parameters. If no character encoding should be set, return |
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156 | * <code>null</code>. |
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157 | * <p> |
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158 | * The default implementation unconditionally returns the value configured |
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159 | * by the <strong>encoding</strong> initialization parameter for this |
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160 | * filter. |
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161 | * |
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162 | * @param request The servlet request we are processing |
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163 | */ |
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164 | protected String selectEncoding(ServletRequest request) { |
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165 | |
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166 | return (this.encoding); |
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167 | |
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168 | } |
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169 | |
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170 | |
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171 | } |
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