从servlet读取响应到html页面

以下是我的要求

Login.html页面以及表单中的用户名和密码文本字段

Login.html-->提交btn->调用LoginServlet

LoginServlet-->来自数据库的已验证用户

成功时-->调用DashboardServlet和DashboardServlet-->调用Dashboard.html

如何读取Dashboard.html上的响应对象[我在这里从DashboardServlet传递用户名]

如果第4步失败-->LoginServlet将再次调用Login.html-->如何读取此页面上的响应对象，假设我将发出警报（用户身份验证失败）

登录servlet

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    System.out.println("I am in doPost of LoginServlet");
    String userName = request.getParameter("username");
    String passWord = request.getParameter("password");

    if(LoginDao.validate(userName, passWord))
    {
        HttpSession session=request.getSession();  
        if(session.isNew())
           {
            //New session creation
              session=request.getSession(true);
           }
            else
            {
               session = request.getSession(false);
            }

         //setting attribute on session
         session.setAttribute("userName",userName);
         //send request to Welcome.jsp page
         //response.sendRedirect("/Dashboard.html");
         response.sendRedirect("/zmcwebadmin/dashBoardServlet");
         response.getWriter().write(String.valueOf(userName));
         System.out.println("I have connected to DB");
    }

    else
    {
        //response.sendRedirect("error.html");
        String data = "User name and password do not match";
        response.setContentType("text/plain");
        response.setCharacterEncoding("UTF-8");
        response.getWriter().write(data);
        /*RequestDispatcher rd = request.getRequestDispatcher("Loginpage.html"); -- This solution works
        rd.forward(request, response);*/
        //response.sendRedirect("Loginpage.html");
        request.setAttribute("error", "Unknown login, try again");
        response.sendRedirect("/zmcwebadmin/html/Login.html");
        //doGet(request, response);

        System.out.println("I have not connected to server");
       }
      }

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


    System.out.println("I am in doGet of dashBoardServlet");
    //New writing on 19th March where initial control given to servlet

        HttpSession session = request.getSession(false); 
        if(session.getAttribute("userName") == null) //session is not created
            response.sendRedirect("/zmcwebadmin/html/LoginPage.html");
        else
            response.sendRedirect("/zmcwebadmin/html/Dashboard.html");
}

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

    System.out.println("I am in doPost of dashBoardServlet");
    String scannerState = request.getParameter("scannerState");
    System.out.println("Dashboard servlet called, scannerState: " + scannerState);
    System.out.println("I am in dashBoardServlet");
    ZebraDbDao zebraDbDao = new ZebraDbDao();
    List<Scanner> scannerList;

    try {
        scannerList = zebraDbDao.getScannerDetail(scannerState);
        System.out.println("I got the scanner list");
        String json = new Gson().toJson(scannerList);
        response.setContentType("application/json");
        response.setCharacterEncoding("UTF-8");
        response.getWriter().write(json);
    } catch (SQLException e) {

        e.printStackTrace();
    } // online scanner
}

仪表板servlet

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    System.out.println("I am in doPost of LoginServlet");
    String userName = request.getParameter("username");
    String passWord = request.getParameter("password");

    if(LoginDao.validate(userName, passWord))
    {
        HttpSession session=request.getSession();  
        if(session.isNew())
           {
            //New session creation
              session=request.getSession(true);
           }
            else
            {
               session = request.getSession(false);
            }

         //setting attribute on session
         session.setAttribute("userName",userName);
         //send request to Welcome.jsp page
         //response.sendRedirect("/Dashboard.html");
         response.sendRedirect("/zmcwebadmin/dashBoardServlet");
         response.getWriter().write(String.valueOf(userName));
         System.out.println("I have connected to DB");
    }

    else
    {
        //response.sendRedirect("error.html");
        String data = "User name and password do not match";
        response.setContentType("text/plain");
        response.setCharacterEncoding("UTF-8");
        response.getWriter().write(data);
        /*RequestDispatcher rd = request.getRequestDispatcher("Loginpage.html"); -- This solution works
        rd.forward(request, response);*/
        //response.sendRedirect("Loginpage.html");
        request.setAttribute("error", "Unknown login, try again");
        response.sendRedirect("/zmcwebadmin/html/Login.html");
        //doGet(request, response);

        System.out.println("I have not connected to server");
       }
      }

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


    System.out.println("I am in doGet of dashBoardServlet");
    //New writing on 19th March where initial control given to servlet

        HttpSession session = request.getSession(false); 
        if(session.getAttribute("userName") == null) //session is not created
            response.sendRedirect("/zmcwebadmin/html/LoginPage.html");
        else
            response.sendRedirect("/zmcwebadmin/html/Dashboard.html");
}

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

    System.out.println("I am in doPost of dashBoardServlet");
    String scannerState = request.getParameter("scannerState");
    System.out.println("Dashboard servlet called, scannerState: " + scannerState);
    System.out.println("I am in dashBoardServlet");
    ZebraDbDao zebraDbDao = new ZebraDbDao();
    List<Scanner> scannerList;

    try {
        scannerList = zebraDbDao.getScannerDetail(scannerState);
        System.out.println("I got the scanner list");
        String json = new Gson().toJson(scannerList);
        response.setContentType("application/json");
        response.setCharacterEncoding("UTF-8");
        response.getWriter().write(json);
    } catch (SQLException e) {

        e.printStackTrace();
    } // online scanner
}

/**
*@参见HttpServlet#doGet（HttpServletRequest请求，HttpServletResponse
*（答复）
*/
受保护的void doGet（HttpServletRequest请求、HttpServletResponse响应）
抛出ServletException、IOException{
//TODO自动生成的方法存根
System.out.println（“我在dashBoardServlet的doGet中”）；
//3月19日的新文章，其中初始控制权授予servlet
HttpSession session=request.getSession（false）；
如果（session.getAttribute（“userName”）==null）//未创建会话
sendRedirect（“/zmcwebadmin/html/LoginPage.html”）；
其他的
sendRedirect（“/zmcwebadmin/html/Dashboard.html”）；
}
/**
*@参见HttpServlet#doPost（HttpServletRequest，HttpServletResponse
*（答复）
*/
受保护的void doPost（HttpServletRequest请求、HttpServletResponse响应）
抛出ServletException、IOException{
//TODO自动生成的方法存根
System.out.println（“我在dashBoardServlet的doPost中”）；
字符串scannerState=request.getParameter（“scannerState”）；
System.out.println（“被调用的仪表板servlet，scannerState:+scannerState”）；
System.out.println（“我在dashBoardServlet中”）；
ZebraDbDao ZebraDbDao=新的ZebraDbDao（）；
列表扫描列表；
试一试{
scannerList=zebraDbDao.getScannerDetail（scannerState）；
System.out.println（“我得到了扫描列表”）；
字符串json=new Gson（）.toJson（扫描列表）；
setContentType（“应用程序/json”）；
响应。setCharacterEncoding（“UTF-8”）；
response.getWriter（）.write（json）；
}捕获（SQLE异常）{
e、 printStackTrace（）；
}//在线扫描仪
}

Dashboard.html

   <script>

  function changeLogoutImage() {
    var image = document.getElementById('logoutbtn'); /* function for logout image*/
    if (image.src.match("_selected")) {
        image.src = "../Images/logout_deselected.png";
    } else {
        image.src = "../Images/logout_selected-18.png";
    }
}

   $(document).ready(function(){ 
   $('#form_logout').submit(function()  
  {
    $form = $(this);
$.post($form.attr('action'), $form.serialize(),  function(responseText)  {
$('#usenameText').text(responseText);                                    
        });
        return false;                                                            
    });
});

函数changeLogoutImage（）{
var image=document.getElementById（'logoutbtn'）；/*用于注销映像的函数*/
if（image.src.match（“\u selected”））{
image.src=“../Images/logout\u deselected.png”；
}否则{
image.src=“../Images/logout_selected-18.png”；
}
}
$（文档）.ready（函数（）{
$（'#表单_注销'）。提交（函数（）
{
$form=$（此项）；
$.post（$form.attr（'action'），$form.serialize（），函数（responseText）{
$（'usenameText'）.text（responseText）；
});
返回false；
});
});

ZMC服务器
用户名

您无需任何额外步骤即可访问响应对象：

但您正在会话中存储警报，例如，

${sessionScope.userName}

。还有一件事：您需要使用jsp访问它们，普通html不行。“我忘了提那件事了！”彼得谢谢你的回答。我限制自己使用jsp，并希望通过html或任何javascript方法实现。恐怕这是不可能的，或者我的知识还不够。您可以访问响应对象，而无需任何额外步骤：

但您正在会话中存储警报，即

${sessionScope.userName}

例如，还有一件事：您需要使用jsp来访问它们，普通html是不行的。“我忘了提那件事了！”彼得谢谢你的回答。我限制自己使用jsp，并希望通过html或任何javascript方法实现。我担心这是不可能的，或者我的知识还不够。