SetCharacterEncodingFilter


1   /*
2    * $Header: /cvsroot/mvnforum/myvietnam/src/net/myvietnam/mvncore/servlet/filter/SetCharacterEncodingFilter.java,v 1.2 2004/06/27 01:20:34 skoehler Exp $
3    * $Revision: 1.2 $
4    * $Date: 2004/06/27 01:20:34 $
5    *
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63  
64  
65  package net.myvietnam.mvncore.servlet.filter;
66  
67  
68  import java.io.IOException  ;
69  import javax.servlet.Filter  ;
70  import javax.servlet.FilterChain  ;
71  import javax.servlet.FilterConfig  ;
72  import javax.servlet.ServletException  ;
73  import javax.servlet.ServletRequest  ;
74  import javax.servlet.ServletResponse  ;
75  
76  
77  /**
78   * <p>Example filter that sets the character encoding to be used in parsing the
79   * incoming request, either unconditionally or only if the client did not
80   * specify a character encoding.  Configuration of this filter is based on
81   * the following initialization parameters:</p>
82   * <ul>
83   * <li><strong>encoding</strong> - The character encoding to be configured
84   *     for this request, either conditionally or unconditionally based on
85   *     the <code>ignore</code> initialization parameter.  This parameter
86   *     is required, so there is no default.</li>
87   * <li><strong>ignore</strong> - If set to "true", any character encoding
88   *     specified by the client is ignored, and the value returned by the
89   *     <code>selectEncoding()</code> method is set.  If set to "false,
90   *     <code>selectEncoding()</code> is called <strong>only</strong> if the
91   *     client has not already specified an encoding.  By default, this
92   *     parameter is set to "true".</li>
93   * </ul>
94   *
95   * <p>Although this filter can be used unchanged, it is also easy to
96   * subclass it and make the <code>selectEncoding()</code> method more
97   * intelligent about what encoding to choose, based on characteristics of
98   * the incoming request (such as the values of the <code>Accept-Language</code>
99   * and <code>User-Agent</code> headers, or a value stashed in the current
100  * user's session.</p>
101  *
102  * @author Craig McClanahan
103  * @version $Revision: 1.2 $ $Date: 2004/06/27 01:20:34 $
104  */
105 
106 public class SetCharacterEncodingFilter implements Filter   {
107 
108 
109     // ----------------------------------------------------- Instance Variables
110 
111 
112     /**
113      * The default character encoding to set for requests that pass through
114      * this filter.
115      */
116     protected String   encoding = null;
117 
118 
119     /**
120      * The filter configuration object we are associated with.  If this value
121      * is null, this filter instance is not currently configured.
122      */
123     protected FilterConfig   filterConfig = null;
124 
125 
126     /**
127      * Should a character encoding specified by the client be ignored?
128      */
129     protected boolean ignore = true;
130 
131 
132     // --------------------------------------------------------- Public Methods
133 
134 
135     /**
136      * Take this filter out of service.
137      */
138     public void destroy() {
139 
140         this.encoding = null;
141         this.filterConfig = null;
142 
143     }
144 
145 
146     /**
147      * Select and set (if specified) the character encoding to be used to
148      * interpret request parameters for this request.
149      *
150      * @param request The servlet request we are processing
151      * @param response The servlet response we are creating
152      * @param chain The filter chain we are processing
153      *
154      * @exception IOException if an input/output error occurs
155      * @exception ServletException if a servlet error occurs
156      */
157     public void doFilter(ServletRequest   request, ServletResponse   response,
158                          FilterChain   chain)
159     throws IOException  , ServletException   {
160 
161         // Conditionally select and set the character encoding to be used
162         if (ignore || (request.getCharacterEncoding() == null)) {
163             String   encoding = selectEncoding(request);
164             if (encoding != null) {
165                 request.setCharacterEncoding(encoding);
166             }
167         }
168 
169         // Pass control on to the next filter
170         chain.doFilter(request, response);
171 
172     }
173 
174 
175     /**
176      * Place this filter into service.
177      *
178      * @param filterConfig The filter configuration object
179      */
180     public void init(FilterConfig   filterConfig) throws ServletException   {
181 
182         this.filterConfig = filterConfig;
183         this.encoding = filterConfig.getInitParameter("encoding");
184         String   value = filterConfig.getInitParameter("ignore");
185 
186         // minhnn begin
187         if (this.encoding != null && this.encoding.equals("")) {
188             // do not allow empty encoding
189             this.encoding = null;
190         }
191         // minhnn end
192 
193         if (value == null)
194             this.ignore = true;
195 
196         // minhnn begin
197         else if (value.equals(""))
198             this.ignore = true;
199         // minhnn end
200 
201         else if (value.equalsIgnoreCase("true"))
202             this.ignore = true;
203         else if (value.equalsIgnoreCase("yes"))
204             this.ignore = true;
205         else
206             this.ignore = false;
207 
208     }
209 
210 
211     // ------------------------------------------------------ Protected Methods
212 
213 
214     /**
215      * Select an appropriate character encoding to be used, based on the
216      * characteristics of the current request and/or filter initialization
217      * parameters.  If no character encoding should be set, return
218      * <code>null</code>.
219      * <p>
220      * The default implementation unconditionally returns the value configured
221      * by the <strong>encoding</strong> initialization parameter for this
222      * filter.
223      *
224      * @param request The servlet request we are processing
225      */
226     protected String   selectEncoding(ServletRequest   request) {
227 
228         return (this.encoding);
229 
230     }
231 
232 
233 }
234
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