输入用户名密码，判断用户名和密码相同，登陆成功，session中保存用户的用户名，进入主页main.jsp，主页有一个退出按钮，点击，回到登陆页login.jsp。要求：退出登录后，如果在浏览器直接输入主页main.jsp，访问不了，直接跳到登陆页
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<html>
<head>
<title>My JSP 'index.jsp' starting page</title>
</head>
<body>
<script type="text/javascript">
function validate(){
if(loginForm.uname.value==""){
alert("账号不能为空!");
return;
}
if(loginForm.upwd.value==""){
alert("密码不能为空!");
return;
}
loginForm.submit();
}
</script>
<form name="loginForm" action="dologin.jsp" method="post">
用户名:<input type="text" name="uname" ><br>
密码: <input type="password" name="upwd" ><br>
<input type="button" value="登录" onClick="validate()">
</form>
</body>
</html>
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
request.setCharacterEncoding("utf-8");
String uname = request.getParameter("uname");
String upwd = request.getParameter("upwd");
if (uname.equals(upwd)){
session.setAttribute("uname", uname);
request.getRequestDispatcher("index.jsp").forward(request,response);
}
else{
response.sendRedirect("no.jsp");
}
%>
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<html>
<head>
<title>My JSP 'index.jsp' starting page</title>
</head>
<body>
<%
String uname=(String)session.getAttribute("uname");
if(uname==null)
response.sendRedirect("login.jsp");
%>
欢迎你<%=uname %>
<a href="logout.jsp">退出登录</a>
</body>
</html>
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<html>
<head>
<title>My JSP 'index.jsp' starting page</title>
</head>
<body>
<h1>登陆失败！！</h1>
<%response.setHeader("refresh", "3;url=login.jsp");%>
</body>
</html>
和上一题一起，在main.jsp中做一个商品展示，里面显示3个商品名和价格 ,每一个后面有一个加入购物车按钮，main.jsp中有一个按钮（或者超链接）可以显示购物车show.jsp 。（选作：在购物车show.jsp中加删除按钮删除商品
<%@ 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>
<title>My JSP 'index.jsp' starting page</title>
</head>
<body bgcolor=#FFccff>
<%
String uname = (String) session.getAttribute("uname");
//如果他是空，说明没登陆，直接访问该页面了
if (uname == null)
response.sendRedirect("login.jsp");
%>
欢迎你<%=uname%><br>
<br>
<a href="tuichu.jsp">退出登录</a>
<hr>
商品展示：
<br> 欢迎进入水果商城：
<br>
<hr>
<form action="show.jsp" method="post">
请选择要加入购物车的商品：<br> <input type="checkbox" name="list" value="荔枝">
荔枝 9.99/kg<br> <input type="checkbox" name="list" value="桃子">
桃子 6.88/kg<br> <input type="checkbox" name="list" value="西瓜">
西瓜 7.99/kg<br>
<hr>
<input type="submit" value="加入购物车">
</form>
</body>
</html>
<%@ 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>
<title>My JSP 'index.jsp' starting page</title>
</head>
<body bgcolor=#eeccft>
<h2>购物车添加的商品有：</h2>
<%
request.setCharacterEncoding("utf-8");
String listName[] = request.getParameterValues("list");
if (listName == null) {
out.print("购物车为空！");
} else {
for (int i = 0; i < listName.length; i++) {
out.print("(" + (i + 1) + ")" + listName[i] + "<br>");
}
}
%>
</body>
</html>
