package com.pv.utils;

 import java.io.IOException;

 import java.io.PrintWriter;

 import javax.servlet.*;

 import javax.servlet.http.HttpServletRequest;

 import javax.servlet.http.HttpServletResponse;

 import javax.servlet.http.HttpSession;

 public class RequestFilter implements Filter  {

     private FilterConfig config;

     //实现初始化方法

     public void init(FilterConfig config){

         this.config = config;

     }

     public void destroy(){

         this.config = null;

     }

     @Override

     public void doFilter(ServletRequest req, ServletResponse res,

             FilterChain chain) throws IOException, ServletException {

         // TODO Auto-generated method stub

         req.setCharacterEncoding("utf-8");

         HttpServletRequest request  = (HttpServletRequest) req;

         HttpServletResponse response  = (HttpServletResponse) res;

         HttpSession session = request.getSession();

         //获取客户请求的页面

         String url = request.getServletPath();

         System.out.println("wangming"+url);

         if((!request.getServletPath().equals("/login.jsp"))

             &&(!request.getServletPath().equals("/solar.jsp"))

             &&(!request.getServletPath().equals("/index.jsp"))){

             System.out.println(request.getServletPath());

             if(session.getAttribute("username")==null){

                 session.invalidate();

                 response.setContentType("text/html;charset=gb2312");

                 PrintWriter out = response.getWriter();

                 out.println("<script language='javascript' type='text/javascript'>");

                 out.println("alert('由于你长时间没有操作,导致Session失效!请你重新登录!');top.location.href='" + request.getContextPath() + "/solar.jsp'");

                 out.println("</script>");

             }else{

                 chain.doFilter(request , response );

             }

         }else{

             chain.doFilter(request , response );

         }

     }

 }

 <session-config>

      <session-timeout>1</session-timeout>

 </session-config>

 <filter>

     <filter-name>RequestFilter</filter-name>

     <filter-class>com.pv.utils.RequestFilter</filter-class>

 </filter>

 <filter-mapping>

     <filter-name>RequestFilter</filter-name>

     <url-pattern>*.jsp</url-pattern>

 </filter-mapping>