java web过滤器之用户登录过滤


package cn.itcast.filters;

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.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

public class UserAccessFilter implements Filter {

 public void doFilter(ServletRequest req, ServletResponse res,

   FilterChain chain) throws IOException, ServletException {

  HttpServletRequest request = (HttpServletRequest) req;

  HttpServletResponse response = (HttpServletResponse) res;

  StringBuffer sb = request.getRequestURL();

  String url = sb.toString();

  HttpSession session = request.getSession(false);

  if (url.contains("/LoginServlet")||url.contains("/ToLoginJspServlet")||url.contains("/login.jsp")) {

   chain.doFilter(request, response);

  } else {

   if (session != null) {

    Object o = session.getAttribute("UserInfo");

    if (o != null) {

     chain.doFilter(request, response);

    } else {

     response.sendRedirect("ToLoginJspServlet");

    }

   } else {

    response.sendRedirect("ToLoginJspServlet");

   }

  }

 }

 public void init(FilterConfig arg0) throws ServletException {

 }

 public void destroy() {

 }

}