web 后端
jsp一共有九大内置对象
- out
- request
- response
- session
- application
- page
- pagecontext
- exception
- config
1.out
- out.println()像客户端打印
- out.flush()讲缓冲区内容输出到客户端
- out.clear()清除缓冲区内容，在flush之后会异常
- out.cleatBuffer()清除，但是不会抛出异常
void.close()关闭输出流
2.requset
3.response
请求转发与请求重定向
4. session
5.application
jsp内置对象实例，实现用户登录
//login.jsp
<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<html>
<head>
<!-- Page title -->
<title>imooc - Login</title>
<!-- End of Page title -->
<!-- Libraries -->
<link type="text/css" href="css/login.css" rel="stylesheet" />
<link type="text/css" href="css/smoothness/jquery-ui-1.7.2.custom.html" rel="stylesheet" />
<script type="text/javascript" src="js/jquery-1.3.2.min.js"></script>
<script type="text/javascript" src="js/easyTooltip.js"></script>
<script type="text/javascript" src="js/jquery-ui-1.7.2.custom.min.js"></script>
<!-- End of Libraries -->
</head>
<body>
<div id="container">
<div class="logo">
<a href="#"><img src="assets/logo.png" alt="" /></a>
</div>
<div id="box">
<form action="dologin.jsp" method="post">
<p class="main">
<label>用户名: </label>
<input name="username" value="" />
<label>密码: </label>
<input type="password" name="password" value="">
</p>
<p class="space">
<input type="submit" value="登录" class="login" style="cursor: pointer;"/>
</p>
</form>
</div>
</div>
</body>
</html>//dologin.jsp
<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
String username ="";
String password ="";
request.setCharacterEncoding("utf-8");//防止中文乱码
username = request.getParameter("username");
password = request.getParameter("password");
//如果用户和密码都等于admin,则登录成功
if("admin".equals(username)&&"admin".equals(password))
{
session.setAttribute("loginUser", username);
request.getRequestDispatcher("login_success.jsp").forward(request, response);
//服务器内部转发 用requset
}
else
{//失败 请求重定向
response.sendRedirect("login_failure.jsp");
}
%>//login_success.jsp
<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<html>
<head>
<!-- Page title -->
<title>imooc - Login</title>
<!-- End of Page title -->
<!-- Libraries -->
<link type="text/css" href="css/login.css" rel="stylesheet" />
<link type="text/css" href="css/smoothness/jquery-ui-1.7.2.custom.html" rel="stylesheet" />
<script type="text/javascript" src="js/jquery-1.3.2.min.js"></script>
<script type="text/javascript" src="js/easyTooltip.js"></script>
<script type="text/javascript" src="js/jquery-ui-1.7.2.custom.min.js"></script>
<!-- End of Libraries -->
</head>
<body>
<div id="container">
<div class="logo">
<a href="#"><img src="assets/logo.png" alt="" /></a>
</div>
<div id="box">
<%
String loginUser = "";
if(session.getAttribute("loginUser")!=null)
{
loginUser = session.getAttribute("loginUser").toString();
//session.getAttribute返回次对话中的指定名称绑定在一起的对象，若没有折返回null
}
%>
欢迎您<font color="red"><%=loginUser%></font>,登录成功！
</div>
</div>
</body>
</html>login_failure.jsp
@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<html>
<head>
<!-- Page title -->
<title>imooc - Login</title>
<!-- End of Page title -->
<!-- Libraries -->
<link type="text/css" href="css/login.css" rel="stylesheet" />
<link type="text/css" href="css/smoothness/jquery-ui-1.7.2.custom.html" rel="stylesheet" />
<script type="text/javascript" src="js/jquery-1.3.2.min.js"></script>
<script type="text/javascript" src="js/easyTooltip.js"></script>
<script type="text/javascript" src="js/jquery-ui-1.7.2.custom.min.js"></script>
<!-- End of Libraries -->
</head>
<body>
<div id="container">
<div class="logo">
<a href="#"><img src="assets/logo.png" alt="" /></a>
</div>
<div id="box">
登录失败！请检查用户或者密码!<br>
<a href="login.jsp">返回登录</a>
</div>
</div>
</body>
</html>
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