用jsp实现一个简易留言页面：
运行结果如图
1.登录页面： login.jsp
登录页面中检测输入是否为空
<%@ page language="java" contentType="text/html; charset=GBK"
pageEncoding="GBK"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="GBK">
<title>登录页面</title>
</head>
<script type="text/javascript">
function check(){
var one=document.forms[0].name.value;
var two=document.forms[0].pwd.value;
if(!one){
alert("不允许为空！");
return false;}
else if(!two){
alert("不允许为空");
return false;}
else {
document.forms[0].action="check.jsp";}
}
</script>
<body>
<form action="" method="post">
姓名<input type="text" name="name"><br><br>
密码<input type="text" name="pwd"><br>
<input type="submit" name="sub" value="提交" onclick="check()">
<input type="reset" name="res" value="重置">
</form>
</body>
</html>
2.验证页面，验证账号及密码。这里我们设置账号为小写的csdn，密码为123456
check.jsp
<%@ page language="java" contentType="text/html; charset=GBK"
pageEncoding="GBK"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="GBK">
<title>验证页面</title>
</head>
<body>
<% request.setCharacterEncoding("GBK");
String name=request.getParameter("name");
String pwd=request.getParameter("pwd");
if((name.equals("csdn"))&&(pwd.equals("123456"))){
out.print("登录成功,3秒后跳转到留言页面");
session.setAttribute("name",name);
response.setHeader("refresh","3;liuyan.jsp");
}
else{
response.setHeader("refresh","2;login.jsp");
}
%>
</body>
</html>
3.留言页面 liuyan.jsp
<%@page import="java.text.SimpleDateFormat"%>
<%@page import="java.util.*"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"
%><%@ page import="java.util.Date"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>留言页面</title>
</head>
<body>
<%if (session.getAttribute("name")==null){%>
<h1>用户还没有登录</h1>
<%}else {%>
<h1>欢迎<%= session.getAttribute("name")%>光临本系统</h1>
<a href="loginout.jsp">注销登录</a>
<h1>简易留言板</h1>
<form method="post" action="getValue.jsp">
<table border="1">
<tr>
<td align="right">留言标题：</td>
<td align="left"><textarea name="title" rows="1" cols="20"></textarea></td>
</tr>
<tr>
<td align="right">留言内容：</td>
<td align="left"><textarea name="content" rows="4" cols="20"></textarea></td>
</tr>
<%
Date d = new Date();
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String time = df.format(d);
session.setAttribute("time", time);
%>
<tr>
<td colspan="2" align="center">
<input type="submit" name="sub" value="提交">
<input type="reset" name="sub" value="重置">
</td>
</tr>
</table>
</form>
<%}%>
</body>
</html>
4.显示留言页面 getValue.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>查看留言</title>
</head>
<body>
<% request.setCharacterEncoding("UTF-8");
String time = session.getAttribute("time").toString();
%>
<%if (session.getAttribute("name")==null){%>
<h1>用户还没有登录</h1>
<%}else {%>
<h1>欢迎<%= session.getAttribute("name")%>登录本系统</h1>
<a href="loginout.jsp">注销登录</a>
<h2>留言板信息如下：</h2>
<h3>留言标题：<%= request.getParameter("title")%></h3>
<h3>留言内容：<%= request.getParameter("content")%></h3>
<h3>留言时间：<%out.print(time);%></h3>
<%}%>
<h1></h1>
</body>
</html>
5.注销登录页面 loginout.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>注销登录</title>
</head>
<body>
<%
session.invalidate();
response.sendRedirect("login.jsp");
%>
<h1>您已成功退出本系统，两秒后跳转回首页，如果没有，请按<a href="login.jsp"></a>这里</h1>
<% response.setHeader("refresh","2;login.jsp");
%>
</body>
</html>
