session保存用户登录

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>登录</title>
</head>
<body>
登录页面<br>
<%
//销毁session
session.invalidate();%>
<form action="testPW.jsp" method="post">
用户名：<input type="text" name="username"/>
密码：<input type="password" name="password"/>
<input type="submit" value="登录"/></form>
</body>
</html>

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
//验证 用户登录信息是否正确
String un= request.getParameter("username");
String pw= request.getParameter("password");
if (un!=""&&pw!="")
{
    //如果正确，就创建session，并跳转到main.jsp
    if(un.equals("tom")&&pw.equals("123"))
    {
        session.setAttribute("username", un);
        //跳转到系统主页面
        response.sendRedirect("Main.jsp");
    }
    else
    {
        //否则提示登陆错误
        out.print("用户名或密码错误");
    }
}
else
{
    out.print("请以正确的方式登录");
}



//%>
</body>
</html>

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>

<% //检查session,取得session信息 
    Object obj=session.getAttribute("username");
    if(obj!=null)
    {
        out.print("欢迎登陆");
    }
    else
    {
        out.print("会话超时，请重新登录系统");
        response.setHeader("refResh", "3;URL=Login.jsp");
    }%>
    主页面
    <br>
    <a href="Login.jsp">退出登录</a>
</body>
</html>

session保存用户登录

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