Question

我要在servlet中创建一个会话，并通过requestDispatcher将其发送到下一个servlet或jsp页面。但是问题在于它不应该在另一个选项卡中。如果创建了会话，则应在下一个选项卡中显示该会话，但是当我在下一个选项卡中输入URL时，它将显示一个空白页面。我不知道为什么？请向我解释为什么会发生这种情况。

Home.jsp

<html>
    <head>
        <title>TODO supply a title</title>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
    </head>
    <body>
        <%
            out.println("Name ::" + session.getAttribute("name"));
            if (session.getAttribute("name") != null) {
//                response.sendRedirect("Main.jsp");
                response.sendRedirect("WelcomeServlet");

                //request.getRequestDispatcher("WelcomeServlet").forward(request, response);
            }
        %>
        <div style="width: 200px;height: 100px;border: 1px solid black;padding: 80px;margin: 50px 200px;">
            <form  action="DispacherDemo" method="POST">
                <input type="text" name="user" placeholder="NAME"/><br/><br>
                <input type="password" name="pass" placeholder="PASSWORD"><br/><br>
                <input type="submit" value="submit">
            </form>
        </div>
    </body>
</html>

Servlet

 protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        out.println("Hello world!!!!");
        try {
            HttpSession session = request.getSession();
            out.println("SESSIONID"+session.getId()+" Name "+session.getAttribute("name"));
            String name = request.getParameter("user");
            String password = request.getParameter("pass");

            if ((password.equals("pass") && name.equals("vinay"))||session.getAttribute("name")!=null) {
                if(session.getAttribute("name")!=null){
                    out.println("Servlet session=="+session.getAttribute("name"));
                    RequestDispatcher rd = request.getRequestDispatcher("WelcomeServlet");
                rd.forward(request, response);
                }else{

                session.setAttribute("name", name);

                RequestDispatcher rd = request.getRequestDispatcher("WelcomeServlet");
               rd.forward(request, response);
                }
            } else {
                out.println("<font color='red'><b>You have entered incorrect password</b></font>");
                RequestDispatcher rd = request.getRequestDispatcher("index.html");
                rd.include(request, response);
            }
        } finally {
            out.close();
        }

    }

WelcomeServlet.java

protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        response.setHeader("Cache-Control", "no-cache, no-store, must-revalidate");
        HttpSession session = request.getSession(false);

        try {
            out.println("Name::::"+session.getAttribute("name"));
            if (session.getAttribute("name")==null) {
                out.println("You have to login first!!!!");

                response.sendRedirect("index.html");
            } else {
                String name = (String) session.getAttribute("name");
                out.println("<h2>Welcome " + name + " " + session.getId() + "</h2>");
                out.println("<br/><a href=\"logoutServlet\">Logout</a>");
            }
        } finally {
            out.close();
        }

    }

如果创建会话，则页面也应该对另一个选项卡可见。

我们可以通过requestDispactcher维护会话，并且在打开新标签页时也可以正常工作吗？

0 个答案: