为什么如果我按 F5 servlet 会话结束？答案

【问题标题】：Why if I press F5 the servlet session ends?为什么如果我按 F5 servlet 会话结束？
【发布时间】：2016-05-30 13:55:36
【问题描述】：

当我从 index.jsp 登录时，我可以看到登录成功的确认信息，但是如果我按下 F5 按钮，则不会考虑上一个会话并创建新会话...所以我必须再次登录并如果我按 F5 再次...

如何使会话持久化？

index.jsp：

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<%@ page session="true"%>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title> Practica3 </title>
<link rel="stylesheet" type="text/css" href="css/structure.css" />
<script type="text/javascript" src="jquery/jquery-1.7.1.js"></script>
<script type="text/javascript">
$(document).ready(function() {
    $(".menu").click(function(event) {
        $('#content').load('Content',{content: $(this).attr('id')});
           });
});
</script>
</head>

<body>

   <!-- Begin Wrapper -->
   <div id="wrapper">

         <!-- Begin Header -->
         <div id="header">

               This is the Header        

         </div>
         <!-- End Header -->

         <!-- Begin Navigation -->
         <div id="navigation">

         <jsp:include page="menu3.jsp" />

         </div>
         <!-- End Navigation -->

         <!-- Begin Faux Columns -->
         <div id="faux">

               <!-- Begin Left Column -->
               <div id="leftcolumn">



               </div>
               <!-- End Left Column -->

               <!-- Begin Content Column -->
               <div id="content">

               <jsp:include page="login.jsp" />

               </div>
               <!-- End Content Column -->



               <!-- Begin Right Column -->
               <div id="rightcolumn">




               </div>
               <!-- End Right Column -->

         </div>    
         <!-- End Faux Columns --> 

         <!-- Begin Footer -->
         <div id="footer">

               This is the Footer       

         </div>
         <!-- End Footer -->

   </div>
   <!-- End Wrapper -->
</body>
</html>

menu.jsp：

 <%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8" session="false"%>

<script type="text/javascript">
$(document).ready(function() {
    $(".menu").click(function(event) {
        $('#content').load('Content',{content: $(this).attr('id')});
        });
});
</script>


<%HttpSession session = request.getSession(true);
System.out.println("cargamos menu.jsp");
System.out.println("        (menu.jsp)Sesion:"+session);
System.out.println("Sesion(user):"+session.getAttribute("user"));
if ((session != null) && (session.getAttribute("user")!=null)) {

%>
<table>
<tr>
<td> <a class="menu" id="logout.jsp" href=#> Logout </a> </td>
</tr>
</table>    
<% }
else {%>
<table>
<tr>
<td> <a class="menu" id="form.jsp" href=#> Registration </a> </td>
<td> <a class="menu" id="login.jsp" href=#> Login </a> </td>
</tr>
</table>
<%}; %>

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<%@ page import="models.BeanLogin" %>


<script type="text/javascript" src="jquery/jquery-1.7.1.js"></script>
<script type="text/javascript" src="jquery/jquery.validate.js"></script>
<script>
$(document).ready(function(){
    $("#registerForm").validate({
        submitHandler: function(form) {
            $('#content').load('logincontroller',$("#registerForm").serialize());
        }
    });
}

);
</script>
</head>
<body>

<% 
BeanLogin login = null;
if (request.getAttribute("login")!=null) {
    login = (BeanLogin)request.getAttribute("login");
}
else {
    login = new BeanLogin();
}
%>

<form id=registerForm action="/Practica3/logincontroller" method="POST">
<table>
<tr> 
<td> User id </td> 
<td> <input type="text" name="user" value="<%=login.getUser() %>" id="user" class="required" minlength="5"/> </td> 
<%  
    if ( login.getError()[0] == 1) {
        %> 
        <td class="error"> Invalid username or password. </td>  
        <% 
    }
%>
</tr>

<tr>
<td> Password </td> 
<td><input type="password" name="password" placeholder="Password"
    value="<%=login.getPassword()%>" id="password" class="required" minlength="8" /></td>
</tr>
<tr> 
<td> <input name="submit" type="submit" value="Enviar"> </td>
</tr>
</table>
</form>

loginOk.jsp：

<script type="text/javascript">
$(document).ready(function() {
        $('#navigation').load('menu.jsp');   
});
</script>

Logged in!

loginController.jsp：

    /**
     * Servlet implementation class logincontroller
     */
    public class logincontroller extends HttpServlet {
        private static final long serialVersionUID = 1L;
        private static DAO Dao;

        /**
         * @throws Exception 
         * @see HttpServlet#HttpServlet()
         */
        public logincontroller() throws Exception {
            super();
            Dao = new DAO();
            // TODO Auto-generated constructor stub
        }

        /**
         * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
         */
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            // TODO Auto-generated method stub

            BeanLogin login = new BeanLogin();
            BeanUtilities.populateBean(login, request);
            try {
                if (login.isComplete() && checkLogin(login)) {

                    HttpSession session = request.getSession();
                    session.setAttribute("user",login.getUser());
                    System.out.println("Se ha hecho el login."+session.toString());
                    System.out.println("User:"+session.getAttribute("user"));
                    session.setMaxInactiveInterval(10);
                    RequestDispatcher dispatcher = request.getRequestDispatcher("loginOk.jsp");
                    if (dispatcher != null) dispatcher.forward(request, response);
                } else {

                request.setAttribute("login",login);
                RequestDispatcher dispatcher = request.getRequestDispatcher("/login.jsp");
                if (dispatcher != null) dispatcher.forward(request, response);

                }
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

        /**
         * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
         */
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            // TODO Auto-generated method stub
            doGet(request,response);
        }

        protected boolean checkLogin(BeanLogin bean) throws SQLException{
            String query = "SELECT id,password FROM ts1.users;";

            ResultSet rs = Dao.executeQuerySQL(query);

            while(rs.next()){

                if (rs.getString(1).equals(bean.getUser()) && rs.getString(2).equals(bean.getPassword())){
                    return true;
                }
            }

            int[] errors = bean.getError();
            errors[0]++;
            bean.setError(errors);
            return false;
        }


    }

web.xml：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>Practica3</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <servlet>
    <description></description>
    <display-name>Content</display-name>
    <servlet-name>Content</servlet-name>
    <servlet-class>controllers.Content</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>Content</servlet-name>
    <url-pattern>/Content</url-pattern>
  </servlet-mapping>
  <servlet>
    <description></description>
    <display-name>formcontroller</display-name>
    <servlet-name>formcontroller</servlet-name>
    <servlet-class>controllers.formcontroller</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>formcontroller</servlet-name>
    <url-pattern>/formcontroller</url-pattern>
  </servlet-mapping>
  <servlet>
    <description></description>
    <display-name>logincontroller</display-name>
    <servlet-name>logincontroller</servlet-name>
    <servlet-class>controllers.logincontroller</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>logincontroller</servlet-name>
    <url-pattern>/logincontroller</url-pattern>
  </servlet-mapping>
  <servlet>
    <description></description>
    <display-name>closesession</display-name>
    <servlet-name>closesession</servlet-name>
    <servlet-class>controllers.closesession</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>closesession</servlet-name>
    <url-pattern>/closesession</url-pattern>
  </servlet-mapping>
  <servlet>
    <description></description>
    <display-name>logoutcontroller</display-name>
    <servlet-name>logoutcontroller</servlet-name>
    <servlet-class>controllers.logoutcontroller</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>logoutcontroller</servlet-name>
    <url-pattern>/logoutcontroller</url-pattern>
  </servlet-mapping>
  <session-config>
    <session-timeout>-1</session-timeout>
  </session-config>
</web-app>

【问题讨论】：

标签： java jsp session servlets

【解决方案1】：

setMaxInactiveInterval() 方法接受时间为秒。您将会话的最大非活动时间设置为 10 秒。将其设置为更长的时间。

【讨论】：

【解决方案2】：

我假设您在 loginController 转发到的页面上按 F5，该页面应该是 loginOK.jsp。您可能会认为您刷新了页面loginOK.jsp，这绝对不是。实际上，您只是刷新了loginController servlet。

原因是在您的loginController 中，您使用forward 代替重定向。当您的loginOK.jsp 出现时，您浏览器上的 URL 仍然是 loginController 而不是 loginOK.jsp。当您刷新此页面时，loginController 会被刷新。结果，为loginController 创建了一个新请求，并创建了一个新的login 对象。当您检查/验证 loginController 中的 login 对象时，检查/验证将失败。因此，loginController 通过您的else 语句转发到login.jsp。

一种可能的解决方案是使用重定向而不是转发：
response.sendRedirect(...);

但是，我建议您按照 MVC 模式重新设计登录流程，并且不要将 java sn-p/code 放在您的 jsp 页面中。
祝你好运。

【讨论】：