JSP数据交互（application、cookie）

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关于作用域的对比：

page<request<session<application

其中page的作用域是当前页面

request的作用域是一次请求（即可以跳转页面）

session的作用域是一次会话（N次请求）

application的作用域是整个应用（N次会话）

Cookie的作用：

对特定对象的追踪

统计网页浏览次数

简化登陆

<%Cookie[] cookies = request.getCookies();if(cookies!=null){for(int i=0;i<cookies.length;i++){if(cookies[i].getName().equals("uname")){  response.sendRedirect(path+"/welcome.jsp");}}}   %>

简单登陆注销

<%@ 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%>">        <title>My JSP 'do.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">-->  </head>    <body>     <form action="/Day02_02/do.jsp" method="post">         <input name="uname"/>          <input name="upwd" type="password"/>          <input type="submit" value="Login"/>      </form>  </body></html>

do.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("utf-8");String uname = request.getParameter("uname");String upwd = request.getParameter("upwd");if ("admin".equals(uname) && "admin".equals(upwd)) {session.setAttribute("uname", uname);request.getRequestDispatcher("success.jsp").forward(request,response);} else {response.sendRedirect("login.jsp");}session.setAttribute("uname", uname);Cookie cookie = new Cookie("uname", uname);Cookie cookiepwd = new Cookie("uname", upwd);response.addCookie(cookie);response.addCookie(cookiepwd);%>

sussece.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("utf-8");String uname = request.getParameter("uname");String upwd = request.getParameter("upwd");if ("admin".equals(uname) && "admin".equals(upwd)) {session.setAttribute("uname", uname);request.getRequestDispatcher("success.jsp").forward(request,response);} else {response.sendRedirect("login.jsp");}session.setAttribute("uname", uname);Cookie cookie = new Cookie("uname", uname);Cookie cookiepwd = new Cookie("uname", upwd);response.addCookie(cookie);response.addCookie(cookiepwd);%>

效果图如下：

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