java验证用户是否已经登录与实现自动登录方法详解

package cn.hongxin.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.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class LoginFilter implements Filter{
 public void init(FilterConfig filterConfig) throws ServletException {
 }
 public void doFilter(ServletRequest request, ServletResponse response,
  FilterChain chain) throws IOException, ServletException {
 //将request强转成htt...
 HttpServletRequest req = (HttpServletRequest) request;
 //获取session
 HttpSession ss = req.getSession();
 //从session中获取user
 if(ss.getAttribute("user")==null){
  System.err.println("你还没有登录");
  req.getSession().setAttribute("msg", "请你先登录");
  //重定向到登录
  HttpServletResponse resp = (HttpServletResponse) response;
  resp.sendRedirect(req.getContextPath()+"/index.jsp");[W2] 
 }else{
  //放行
  chain.doFilter(request, response);
 }
 }
 public void destroy() {
 }
}

 login
 cn.itcast.filter.LoginFilter
 
 
 login
 /jsps/*
 /views/*
 

 
 ">
  Name:

  auto:
  不自动登录
  

  1天

  1周

  
 
 
 
 你已经登录了:${name}

 退出
 

public void doPost(HttpServletRequest request, HttpServletResponse response)
  throws ServletException, IOException {
 //接收用户姓名
 String name = request.getParameter("name");
 String auto = request.getParameter("auto");
 //将用户信息放到session
 request.getSession().setAttribute("name",name);
 //判断auto是否是-1
 if(!auto.equals("-1")){
  int day = Integer.parseInt(auto);//1|7
  int secOnds= 60*60*24*day;
  //声明COOKIE
  COOKIE c = new COOKIE("autoLogin",name);
  c.setMaxAge(seconds);
  c.setPath(request.getContextPath());
  //保存COOKIE
  response.addCOOKIE(c);
 }
 }

public void doFilter(ServletRequest request, ServletResponse response,
  FilterChain chain) throws IOException, ServletException {
 //在这儿读取COOKIE
 HttpServletRequest req = (HttpServletRequest) request;
 //获取所的有COOKIE
 COOKIE[] cs = req.getCOOKIEs();
 if(cs!=null){
  for(COOKIE c:cs){
  if(c.getName().equals("autoLogin")){//如果存在自动登录的COOKIE
   String value = c.getValue();//用户名称
   //登录成功是指
   req.getSession().setAttribute("name", value);
   break;
  }
  }
 }
 //不管是否自动登录成
 chain.doFilter(request, response);
 }

 auto
 cn.itcast.filter.AutoFilter
 
 
 auto
 /*
 

System.err.println("用户退出");
 //删除整个session
 request.getSession().invalidate();
 COOKIE c = new COOKIE("autoLogin", "ddd");
 c.setMaxAge(0);
 c.setPath(request.getContextPath());
 response.addCOOKIE(c);
// request.getSession().removeAttribute("name");
 response.sendRedirect(request.getContextPath()+"/index.jsp");