jsp实现用户自动登录功能

理解并掌握Cookie的作用以及利用cookie实现用户的自动登录功能，实现下图效果

当服务器判断出该用户是首次登录的时候，会自动跳转到登录界面等待用户登录，并填入相关信息。通过设置Cookie的有效期限来保存用户的信息，关闭浏览器后，验证是否能够自动登录，若能登录，则打印欢迎信息；否则跳转到登录页面。

login.jsp

%@ page language="java" import="java.util.*" pageEncoding="utf-8"%
%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%
%request.setCharacterEncoding("GB2312"); %
!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
html
 head
 base href="%=basePath%" rel="external nofollow" rel="external nofollow" 
 
 titleMy JSP 'login.jsp' starting page/title
 
 meta http-equiv="pragma" content="no-cache"
 meta http-equiv="cache-control" content="no-cache"
 meta http-equiv="expires" content="0" 
 meta http-equiv="keywords" content="keyword1,keyword2,keyword3"
 meta http-equiv="description" content="This is my page"
 !--
 link rel="stylesheet" type="text/css" href="styles.css" rel="external nofollow" rel="external nofollow" 
 --
 script type="text/javascript"
 window.onload = function(){
  //获取submit
  var submit = document.getElementById("submit");
  var name = document.getElementById("name");
  //为submit绑定单击响应函数
  submit.onclick = function(){
  
  times = document.getElementsByName("time");
  var count=0;
  for(var i=0;itimes.length;i++){
   if(times[i].checked == true){
   count++;
   }
  }
  if(count=2){
   alert("只能选择一个选项");
   return false;
  }
  
  }; 
  
 };
 
 /script
 /head
 
 body
 !-- 设置html页面 --
 form action="sucess.jsp" method="post"
 用户名：input name="username" /br/
  input type="checkbox" name="time" value="notSave" /不保存
  input type="checkbox" name="time" value="aDay" /一天
  input type="checkbox" name="time" value="aWeek" /一周
  input type="checkbox" name="time" value="forever" /永久
  br/br/
  input type="submit" name="submit" id="submit" value="登录"/
 /form
 % 
 //读取session值
 String val= (String)session.getAttribute("name");
 //如果session不存在
 if(val==null){
  val ="不存在";
 }
 out.print("当前""+val+""用户可自动登录");
 %

 /body
/html

sucess.jsp

%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%
%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%

!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
html
 head
 base href="%=basePath%" rel="external nofollow" rel="external nofollow" 
 
 titleMy JSP 'show.jsp' starting page/title
 
 meta http-equiv="pragma" content="no-cache"
 meta http-equiv="cache-control" content="no-cache"
 meta http-equiv="expires" content="0" 
 meta http-equiv="keywords" content="keyword1,keyword2,keyword3"
 meta http-equiv="description" content="This is my page"
 !--
 link rel="stylesheet" type="text/css" href="styles.css" rel="external nofollow" rel="external nofollow" 
 --

 /head 
 body 
%
 //获取username
 String name = request.getParameter("username");
 //判断用户名是否存在
 if(name != null  !name.trim().equals("")){ 
 String[] time = request.getParameterValues("time");
 //设置session值，便于login页面读取
 session.setAttribute("name", name);
 //设置Cookie
 Cookie Cookie = new Cookie("name",name);
 //根据提交选项设置cookie保存时间
 if(time != null){
  for(int i=0;itime.length;i++){
  //不保存Cookie
  if(time[i].equals("notSave")){
   Cookie.setMaxAge(0); 
  }
  //保存一天Cookie
  if(time[i].equals("aDay")){
   Cookie.setMaxAge(60*60*24);
  }
  //保存一周Cookie
  if(time[i].equals("aWeek")){
   Cookie.setMaxAge(60*60*24*7);
  }
  //永久保存Cookie，设置为100年
  if(time[i].equals("forever")){
   Cookie.setMaxAge(60*60*24*365*100);
  }
  }
 }  
 
 //在客户端保存Cookie
 response.addCookie(Cookie);
 } 
 else{%
  %--用户名不存在则进行判断是否已有cookie --%
 %
 //获取cookie
 Cookie[] cookies = request.getCookies();
 
 //cookie存在
 if(cookies != null  cookies.length  0){
  for(Cookie cookie:cookies){
  //获取cookie的名字
  String cookieName = cookie.getName();
  //判断是否与name相等
  if(cookieName.equals("name")){
   //获取cookie的值
   String value = cookie.getValue();
   name = value;
   }
  }
  }
 }
 if(name != null  !name.trim().equals("")){
 out.print("您好: " + name+"欢迎登录");
 }
 else{//否则重定向到登录界面
  out.print("您还没有注册，2秒后转到注册界面！");
 response.setHeader("refresh","2;url=login.jsp");
 %
 如果没有自动跳转，请点击a href="login.jsp" rel="external nofollow" 此处/a进行跳转
 %
 //response.sendRedirect("login.jsp");
 }
%
 
 /body
/html

实现效果：

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