asp.net 请求参数错误异常处理

package com.accp.filter;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
public class MyFilter extends HttpServlet implements Filter {
 public void doFilter(ServletRequest request, ServletResponse response,
   FilterChain chain) throws IOException, ServletException {
 
  HttpServletRequest arg0 =(HttpServletRequest)request;
  arg0.getSession().setAttribute("eurl", arg0.getRequestURI());
  chain.doFilter(request, response);
    /***
     *  类需要继承HttpServlet  和 实现接口 Filter (过滤器)
     *  添加一个doFilter 方法（右击选择 Source---- Override/mplement Methods）
     *  定义HttpServletRequest,变量arg0 接收 request （需要转换类型）
     *  arg0.getSession().setAttribute("ErrorUrl", arg0.getRequestURI());
     */
 }
 
 public void init(FilterConfig filterConfig) throws ServletException {
  // TODO Auto-generated method stub
  
 } 
}
------------------Web.Xml的配置
 <filter>
   <filter-name>names</filter-name>
   <filter-class>com.accp.filter.MyFilter</filter-class>
  </filter>
  <filter-mapping>
 
    <filter-name>names</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>
  <error-page>
    <error-code>500</error-code>
    <location>/Error.jsp</location>
  </error-page>