import javax.servlet.*; import java.io.IOException;
/** * <p>Filter that sets the character encoding to be used in parsing the * incoming request, either unconditionally or only if the client did not * specify a character encoding. Configuration of this filter is based on * the following initialization parameters:</p> * <ul> * <li><strong>encoding</strong> - The character encoding to be configured * for this request, either conditionally or unconditionally based on * the <code>ignore</code> initialization parameter. This parameter * is required, so there is no default.</li> * <li><strong>ignore</strong> - If set to "true", any character encoding * specified by the client is ignored, and the value returned by the * <code>selectEncoding()</code> method is set. If set to "false, * <code>selectEncoding()</code> is called <strong>only</strong> if the * client has not already specified an encoding. By default, this * parameter is set to "true".</li> * </ul> * * <p>Although this filter can be used unchanged, it is also easy to * subclass it and make the <code>selectEncoding()</code> method more * intelligent about what encoding to choose, based on characteristics of * the incoming request (such as the values of the <code>Accept-Language</code> * and <code>User-Agent</code> headers, or a value stashed in the current * user's session.</p> * * @author <a href="mailto:jwtronics@yahoo.com">John Wong</a> * * @version $Id: SetCharacterEncodingFilter.java,v 1.1 2002/04/10 13:59:27 johnwong Exp $ */
public class SetCharacterEncodingFilter implements Filter {
// ----------------------------------------------------- Instance Variables
/** * The default character encoding to set for requests that pass through * this filter. */ protected String encoding = null;
/** * The filter configuration object we are associated with. If this value * is null, this filter instance is not currently configured. */ protected FilterConfig filterConfig = null;
/** * Should a character encoding specified by the client be ignored? */ protected boolean ignore = true;
// --------------------------------------------------------- Public Methods
/** * Take this filter out of service. */ public void destroy() {
this.encoding = null; this.filterConfig = null;
}
/** * Select and set (if specified) the character encoding to be used to * interpret request parameters for this request. * * @param request The servlet request we are processing * @param result The servlet response we are creating * @param chain The filter chain we are processing * * @exception IOException if an input/output error occurs * @exception ServletException if a servlet error occurs */ public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
// Conditionally select and set the character encoding to be used if (ignore || (request.getCharacterEncoding() == null)) { String encoding = selectEncoding(request); if (encoding != null) request.setCharacterEncoding(encoding); }
// Pass control on to the next filter chain.doFilter(request, response);
}
/** * Place this filter into service. * * @param filterConfig The filter configuration object */ public void init(FilterConfig filterConfig) throws ServletException {
this.filterConfig = filterConfig; this.encoding = filterConfig.getInitParameter("encoding"); PropsUtil.ENCODING = this.encoding; String value = filterConfig.getInitParameter("ignore"); if (value == null) this.ignore = true; else if (value.equalsIgnoreCase("true")) this.ignore = true; else if (value.equalsIgnoreCase("yes")) this.ignore = true; else this.ignore = false;
}
// ------------------------------------------------------ Protected Methods
/** * Select an appropriate character encoding to be used, based on the * characteristics of the current request and/or filter initialization * parameters. If no character encoding should be set, return * <code>null</code>. * <p> * The default implementation unconditionally returns the value configured * by the <strong>encoding</strong> initialization parameter for this * filter. * * @param request The servlet request we are processing */ protected String selectEncoding(ServletRequest request) {
return (this.encoding);
}
}
|