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[Java教程]jsp的session完成登陆功能


login.jsp:

 1 <%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%> 2 <% 3 String path = request.getContextPath(); 4 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; 5 %> 6  7 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 8 <html> 9  <head>10   <base href="<%=basePath%>">11   12   <title>用户登录</title>13   14   <meta http-equiv="pragma" content="no-cache">15   <meta http-equiv="cache-control" content="no-cache">16   <meta http-equiv="expires" content="0">  17   <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">18   <meta http-equiv="description" content="This is my page">19   <!--20   <link rel="stylesheet" type="text/css" href="styles.css">21   -->22 23  </head>24  25  <body>26   <h1>用户登录</h1>27   <form action="check" method="post">28     <table border="1" width="250px">29       <tr><td>用户名:</td><td><input type="text" name="userId" /></td></tr>30       <tr><td>密码:</td><td><input type="password" name="passwd" /></td></tr>31       <tr><td></td><td><input type="submit" value="提交" /></td></tr>32     </table>33   </form>34  </body>35 </html>

welcom.jsp

 1 <%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%> 2 <% 3 String path = request.getContextPath(); 4 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; 5 %> 6  7 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 8 <html> 9  <head>10   <base href="<%=basePath%>">11   12   <title>My JSP 'welcome.jsp' starting page</title>13   14   <meta http-equiv="pragma" content="no-cache">15   <meta http-equiv="cache-control" content="no-cache">16   <meta http-equiv="expires" content="0">  17   <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">18   <meta http-equiv="description" content="This is my page">  19  </head>20   <%21     String user=(String) session.getAttribute("user");22     if(user==null){23     %>24     <jsp:forward page="login.jsp" />25     <%} %>26  <body>27 热烈欢迎您:<%=user %>28  </body>29 </html>

web.

 1 <??> 2 <web-app version="2.5"  3   ="http://java.sun.com/  4   ="http://www.w3.org/2001/  5   xsi:schemaLocation="http://java.sun.com/ 6   http://java.sun.com/> 7  <display-name></display-name>   8  <welcome-file-list> 9   <welcome-file>index.jsp</welcome-file>10  </welcome-file-list>11  <servlet>12    <servlet-name>CheckUser</servlet-name>13    <servlet-class>servlet.CheckUser</servlet-class>14  </servlet>15  <servlet-mapping>16    <servlet-name>CheckUser</servlet-name>17    <url-pattern>/check</url-pattern>18  </servlet-mapping>19  20 </web-app>

CheckUser.java

 1 package servlet; 2  3 import java.io.IOException; 4  5 import javax.servlet.RequestDispatcher; 6 import javax.servlet.ServletException; 7 import javax.servlet.http.HttpServlet; 8 import javax.servlet.http.HttpServletRequest; 9 import javax.servlet.http.HttpServletResponse;10 import javax.servlet.http.HttpSession;11 12 public class CheckUser extends HttpServlet {13   @Override14   protected void doPost(HttpServletRequest request,15       HttpServletResponse response) throws ServletException, IOException {16       request.setCharacterEncoding("UTF-8");17       String userId=request.getParameter("userId");18       String passwd=request.getParameter("passwd");19       20       if(userId!=null&&passwd!=null&&userId.equals("gys")&&passwd.equals("gys")){21         HttpSession session=request.getSession();22         session.setAttribute("user", userId);23         RequestDispatcher dispatcher=request.getRequestDispatcher("/welcome.jsp");24         dispatcher.forward(request, response);25       }26       else{27         RequestDispatcher dispatcher=request.getRequestDispatcher("/login.jsp");28         dispatcher.forward(request, response);29       }30   }31 }