jsp邮箱登录页面及response对象的转发和重定向
jsp邮箱登录页面；
首先我们新建一个jsp，写邮箱登录页面；
<%@ 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 'index.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="reg"method="post">
邮箱：<input type="text" name="email" /><br />
密码：<input type="password" name="pwd" /><br />
<input type="submit" value="登录" />
</form>
</body>
</html>
效果如下；
接下来我们试着用getParameter方法获取到我们输入的值，新建reg.jsp，在reg中显示出来；
<%@ 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 'reg.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>
<%
String email = request.getParameter("email");
out.println("你的邮箱是："+email);
String pwd = request.getParameter("pwd");
out.println("你的密码是："+pwd);
%>
<br>
</body>
</html>
效果如下；
response对象的转发和重定向；
转发（forward）：直接转发；客户端和浏览器只发出一次请求，Servlet、HTML、jsp或其他信息资源，由第一个信息资源响应请求，在请求对象request中，保存的对象对于每个信息资源是共享的。
重定向（redirect）：简介转发；实际是两次请求，服务器端在响应第一次请求的时候，让浏览器再向另一个URL发出请求，从而打到转发的目的。
还是很难理解的，我们用一段代码来间接的感受一下，在刚才的邮箱登录代码的基础上改一下
index.jsp代码；
<%@ 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 'index.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>
<%
//定义一个msg用来接收错误信息
String msg = "";
msg = (String)request.getAttribute("msg");
if(msg==null){
msg = "";
}
%>
<form action="reg.jsp"method="post">
邮箱：<input type="text" name="name" /><br />
密码：<input type="password" name="pwd" /><br />
<%= msg %>
<input type="submit" value="登录" />
</form>
</body>
</html>
reg.jsp代码
失败就是转发；成功则是重定向。
<%@ 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 'reg.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>
<% String pwd = request.getParameter("pwd");
String name = request.getParameter("name");
//因为这里只为示范就不连接数据库了
//直接定值
if("lisi".equals(name) && "123456".equals(pwd)){
//如果正确则跳到成功页面succes.jsp
//重定向
response.sendRedirect("succes.jsp");
}else{
//如果失败则跳转到登录页面，并且输出错误信息
//转发
request.setAttribute("msg", "密码错误!");
request.getRequestDispatcher("index.jsp").forward(request, response);
}
%>
<br>
</body>
</html>
succes.jsp代码
<%@ 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 'email.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>
<h1 style="color: green;text-align: center;" >登录成功！</h1>
</body>
</html>
下面是效果图；
首先是登录页面的效果图；
这里的域名是http://localhost:8080/Text/index.jsp；
接下来是登录成功的截图；
这里的域名为http://localhost:8080/Text/succes.jsp；
接下来是登录失败的截图；
可是这里的域名却为http://localhost:8080/Text/reg.jsp；
但是我们的代码确实是写的跳到index.jsp，可是却显示的是reg.jsp
//因为这里只为示范就不连接数据库了
//直接定值
if("lisi".equals(name) && "123456".equals(pwd)){
//如果正确则跳到成功页面succes.jsp
//重定向
response.sendRedirect("succes.jsp");
}else{
//如果失败则跳转到登录页面，并且输出错误信息
//转发
request.setAttribute("msg", "密码错误!");
request.getRequestDispatcher("index.jsp").forward(request, response);
这就像A找B借钱，可B没有，所以B找C借，但是A不知道B找C借钱。那么A还钱只会还给B不会还给C，再由B还给C。
所以这里等于reg.jsp转发了index.jsp的页面内容但是域名还是自己的；类似于我们的qq转发的说说类似；
如果还有不解，可找作者私聊