Filter问题！！

【Servlet filter】:
package com.ite.softdev.offical.sysman.signon.web;import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import java.net.URL;
import com.ite.softdev.offical.common.utility.UtilDebug;/**
 * <p>Title: 中国大唐集团本部办公系统平台</p>
 * <p>Description:用户登录过滤程序：SignOnFilter.java </p>
 * <p>Copyright: Copyright (c) 2004</p>
 * <p>Company: 长沙亿泰科技有限公司2</p>
 * @author [email protected]
 * @version 1.0
 */public class SignOnFilter
    implements Filter {  public static final String module = SignOnFilter.class.getName();
  public static final String FORM_SIGNON_URL = "index.jsp";
  private FilterConfig Config = null;
  //Handle the passed-in FilterConfig
  public void init(FilterConfig Config) {
    this.Config = Config;  }  //Process the request/response pair
  public void doFilter(ServletRequest req, ServletResponse res,
                       FilterChain chain) throws IOException, ServletException {
    try {
      res.setContentType("text/html;charset=GBK");
      String strURL = new String( ( (HttpServletRequest) req).
                                 getRequestURL());
      if (strURL.endsWith("index.jsp") || strURL.endsWith("不过滤的jsp2.jsp"))
          {
            //res.sendRedirect("main.jsp");
  
          chain.doFilter(req, res);
      }
    }
      catch (ServletException sx) {
        Config.getServletContext().log(sx.getMessage());
      }
      catch (IOException iox) {
        Config.getServletContext().log(iox.getMessage());
      }
  }  /**
  public void validateSignOn(ServletRequest req, ServletResponse res,
                       FilterChain filter) throws IOException, ServletException
  {  }
  **/
  public void destroy() {
    this.Config = null;  }
}
【jsp]】
<%@ page contentType="text/html; charset=GBK" %>
<%@ page import ="com.ite.softdev.offical.common.utility.Test" %><body leftmargin="0" topmargin="0" marginwidth="0" marginheight="0" >
<form name="userSignon" action="j_signon_check" method="POST">
<table width="100%" height=100% border="0" align="center" cellspacing="0" cellpadding=0 bgcolor="#ffa600">
  <tr>
    <td height="100%" width=100% colspan="0" align=center valign=middle>
      <table width="770" height="450" border="0" cellpadding="0" cellspacing="0" style="border: 1px solid #000000">
        <tr>
          <td colspan="3" valign="bottom" background="images/signon.jpg" />
              <table width="100%" height=150 border="0" cellspacing="2" cellpadding=0>
                <tr>
                  <td align="right" valign="middle">
                  <font color="#FFFFFF">用户名：</font>&nbsp;
                  <input name="textfield" type="text" size="10" class="logintext">&nbsp;&nbsp;<font color="#FFFFFF">
                  密码：</font>&nbsp;<input name="textfield2" type="password" size="10" class="logintext">&nbsp;&nbsp;
                  <input type="image" src="images/login.gif" size=3>
                   <input type="checkbox" value="j_remember_username" size=3>  </td>
                  <td valign="middle" width=60 nowrap></td>
       </tr>
              </table>
            </td>
        </tr>
      </table> </td>
  </tr>
</table>
</form>
</body>
</html>
【xml]
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
  <filter>
    <filter-name>SignOnFilter</filter-name>
    <filter-class>com.ite.softdev.offical.sysman.signon.web.SignOnFilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>SignOnFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>
</web-app>