<filter>  
  <filter-name>SessionInvalidate</filter-name>  
  <filter-class>com.tp.action.SessionCheckFilter</filter-class> //过滤器核心类的class地址 
  <init-param>  
   <param-name>checkSessionKey</param-name> //session中需要检查的key 
   <param-value>users</param-value>  
  </init-param>  
  <init-param>  
   <param-name>redirectURL</param-name> //过滤重定向的地址 
   <param-value>/login.jsp</param-value>  
  </init-param>  
  <init-param>  
   <param-name>notCheckURLList</param-name> //不需要过滤的jsp 
   <param-value>/login.jsp</param-value>  
  </init-param>  
 </filter>  
 <filter-mapping>  
  <filter-name>SessionInvalidate</filter-name> //需要过滤的文件 
  <url-pattern>*.jsp</url-pattern>  
 </filter-mapping> 

package com.tp.action; 
import java.io.IOException;  
import java.util.HashSet;  
import java.util.Set;  
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.HttpServletRequest;  
import javax.servlet.http.HttpServletResponse;  
import javax.servlet.http.HttpSession;  
/** 
 * 用于检测用户是否登陆的过滤器，如果未登录，则重定向到指的登录页面 配置参数 checkSessionKey 需检查的在 Session 中保存的关键字 
 * redirectURL 如果用户未登录，则重定向到指定的页面，URL不包括 ContextPath notCheckURLList 
 * 不做检查的URL列表，以分号分开，并且 URL 中不包括 ContextPath 
 */  
public class SessionCheckFilter implements Filter {  
 protected FilterConfig filterConfig = null;  
 private String redirectURL = null;  
 private Set<String> notCheckURLList = new HashSet<String>();  
 private String sessionKey = null;  
 @Override  
 public void destroy() {  
  notCheckURLList.clear();  
 }  
 @Override  
 public void doFilter(ServletRequest servletRequest,  
   ServletResponse servletResponse, FilterChain filterChain)  
   throws IOException, ServletException {  
  HttpServletRequest request = (HttpServletRequest) servletRequest;  
  HttpServletResponse response = (HttpServletResponse) servletResponse;  
  HttpSession session = request.getSession();  
  if (sessionKey == null) {  
   filterChain.doFilter(request, response);  
   return;  
  }  
  if ((!checkRequestURIIntNotFilterList(request))  
    && session.getAttribute("users") == null) {  
     response.sendRedirect(request.getContextPath() + redirectURL);  
   return;  
  }  
  filterChain.doFilter(servletRequest, servletResponse);  
 }  
 private boolean checkRequestURIIntNotFilterList(HttpServletRequest request) {  
  String uri = request.getServletPath()  
    + (request.getPathInfo() == null ? "" : request.getPathInfo());  
  String temp = request.getRequestURI(); 
  temp = temp.substring(request.getContextPath().length() + 1);  
  // System.out.println("是否包括："+uri+";"+notCheckURLList+"=="+notCheckURLList.contains(uri));  
  return notCheckURLList.contains(uri);  
 }  
 @Override  
 public void init(FilterConfig filterConfig) throws ServletException {  
  this.filterConfig = filterConfig;  
  redirectURL = filterConfig.getInitParameter("redirectURL");  
  sessionKey = filterConfig.getInitParameter("checkSessionKey");  
  String notCheckURLListStr = filterConfig  
    .getInitParameter("notCheckURLList");  
  if (notCheckURLListStr != null) {  
   System.out.println(notCheckURLListStr);  
   String[] params = notCheckURLListStr.split(",");  
   for (int i = 0; i < params.length; i++) {  
    notCheckURLList.add(params[i].trim());  
   }  
  }  
 }  
}