文件共有四个web.xml、login.jsp、logout.jsp、welcome.jsp四个文件
测试环境：Tomcat 6.0.x
假设项目名称是LoginSample，我的目录结构是这样的
...\webapps\LoginSample\WEB-INF\web.xml
...\webapps\LoginSample\login.jsp
...\webapps\LoginSample\logout.jsp
...\webapps\LoginSample\welcome.jsp
web.xml源码清单：
<web-app xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee " version="2.4"> <welcome-file-list> <welcome-file>welcome.jsp</welcome-file> </welcome-file-list> </web-app>
login.jsp源码清单：
<%@ page contentType="text/html;charset=UTF-8" %> <html> <head> <title>JSP简单登录实例</title> </head> <body> <h2>请登录</h2> <form method="POST" > Login Name: <input type="text"><br> Login Password: <input type="text" ><br> <input type="submit" value="Send"><br> <form> <% if (request.getParameter("Name") != null && request.getParameter("Password") != null) { String Name = request.getParameter("Name"); String Password = request.getParameter("Password"); if (Name.equals("a") && Password.equals("a")) { session.setAttribute("Login", "OK"); session.setAttribute("myCount", new Integer(1)); response.sendRedirect("welcome.jsp"); } else { %> 登录失败:用户名或密码不正确～ <% } } %> </body> </html>
logout.jsp源码清单：
<%@ page contentType="text/html;charset=UTF-8" %> <html> <% session.setAttribute("Login", ""); %> <body> <h2>你已经退出登录</h2> </body> </html>
welcome.jsp源码清单：
<%@ page contentType="text/html" pageEncoding="UTF-8" import="java.util.*"%> <html> <body> <h2>欢迎页面(测试session)</h2> <% String Login = (String)session.getAttribute("Login"); int nCount=0; if (Login != null && Login.equals("OK")) { Integer myCount = (Integer)session.getAttribute("myCount"); if(myCount!=null) { nCount = myCount.intValue(); nCount = nCount + 1; session.setAttribute("myCount",new Integer(nCount)); } %> 登录成功,myCount=<%=nCount%></br> <input type=button value="退出"> <% } else { %> <jsp:forward page="login.jsp"/> <% } %> </body> </html>