使用Filter转换字符集

1，加入类 com.ddy.struts.filter.SetCharacterEncodingFilter

package com.ddy.struts.filter; 
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:[e-mail]">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");
  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); 
 } 
}// EOC

 

2，修改WEB.XML，配置filter

   <filter>
   <filter-name>Set Character Encoding</filter-name>
   <filter-class>
    com.ddy.struts.filter.SetCharacterEncodingFilter
   </filter-class>
   <init-param>
    <param-name>encoding</param-name>
    <param-value>GB2312</param-value>
   </init-param>
   <init-param>
    <param-name>ignore</param-name>
    <param-value>true</param-value>
   </init-param>
  </filter>
  <filter-mapping>
   <filter-name>Set Character Encoding</filter-name>
   <servlet-name>action</servlet-name>
  </filter-mapping> 

 

3，设定jsp页面的编码（必须于上面encoding标签中设定一致）

     <%@ page language="java" contentType="text/html; charset=GB2312"
              pageEncoding="GB2312"%>