做了一个登陆页面login.jsp，输入用户名和设定的密码，经过check.jsp，跳转进入success.jsp
success点jsp实现的功能是显示“Hello！ +之前输入的用户名”可是我运行出来的结果是
“hello ！null”，没有达到预期的效果
以下是各个页面的代码
login.jsp的代码
<%@ page language="java" import="java.util.*" pageEncoding="gb2312"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
</head>
<body>
<form name="f1" id="f1" action="check.jsp" method="post" >
<table>
<tr>
<td>用户名:</td>
<td><input type="text" name="username"></td>
</tr>
<tr>
<td>密码：</td>
<td><input type="password" name="password"></td>
</tr>
<tr>
<td><input type="submit" name="submit" value="提交"></td>
</table>
</form>
</body>
</html>
check.jsp的代码
<%
String s_name="";
String s_pass="";
s_name=request.getParameter("username");
s_pass=request.getParameter("password");
if("admin".equals(s_name)&&"pass".equals(s_pass))
{
response.sendRedirect("success.jsp");
response.setStatus(HttpServletResponse.SC_MOVED_PERMANENTLY);
response.setHeader("Location","success.jsp");
}
else
{
response.sendRedirect("login.jsp");
response.setStatus(HttpServletResponse.SC_MOVED_PERMANENTLY);
response.setHeader("Location","login.jsp");
}
%>
success.jsp页面的代码
<%@ page language="java" import="java.util.*" pageEncoding="gb2312"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
</head>
<body>
<center><%String a1=request.getParameter("username"); %>
<h1>Hello! <%=a1 %></h1>
</center>
</body>
</html>
------解决方案--------------------
你在check.jsp那里把response.sendRedirect("success.jsp");
改成response.sendRedirect("succeed.jsp?s_name="+username);
因为session他只保存一次页面跳转后的值，如果要继续为下一页服务，就要传参
------解决方案--------------------
check.jsp的代码
<%
String s_name="";
String s_pass="";
s_name=request.getParameter("username");
s_pass=request.getParameter("password");
if("admin".equals(s_name)&&"pass".equals(s_pass))
{
request.getSession(false).setAttribute("userName", s_name);
response.sendRedirect("success.jsp");
response.setStatus(HttpServletResponse.SC_MOVED_PERMANENTLY);
response.setHeader("Location","success.jsp");
}
else
{
response.sendRedirect("login.jsp");
response.setStatus(HttpServletResponse.SC_MOVED_PERMANENTLY);
response.setHeader("Location","login.jsp");
}
%>
<%@ page language="java" import="java.util.*" pageEncoding="gb2312"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
</head>
<body>
<center><%Object userNameObj = request.getSession(false).getAttribute("userName");
String userName = new String();
userName = userNameObj != null ? userName.toString() : "Hey, guy. You haven't signed on yet.Get to sign on first then you are alowed to use this page.";%>
<h1>Hello! <%=userName %></h1>
</center>
</body>
</html>
------解决方案--------------------
你用的是重定向 所以不是同一个request
这里应该用转发
------解决方案--------------------
check.jsp里，sendRedirect和下面setStatus+setHeader有一个是多余的
浏览器会重定向到success.jsp，要获取到前面的用户信息，可以像一楼等传递请求参数，或者服务器把数据保存起来，像2楼一样的用session