java - jsp:forward 删除jsp页面中的所有html

Question

我对使用 jsp 和 servlet 很陌生，所以请耐心等待。我正在构建的网站有一个登录表单来访问其余页面。当您登录时，它会使用您的用户名设置一个 cookie，其目的是让其他页面在您尝试访问它们时检查此 cookie。

登录表单在操作中运行此登录 Servlet:

public class LoginServlet extends HttpServlet implements Constants {

/**
 * Processes requests for both HTTP <code>GET</code> and <code>POST</code>
 * methods.
 *
 * @param request servlet request
 * @param response servlet response
 * @throws ServletException if a servlet-specific error occurs
 * @throws IOException if an I/O error occurs
 */
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {


    String Username = request.getParameter("username");
    String password = request.getParameter("password");

    if (StringUtils.isStringEmpty(Username) || StringUtils.isStringEmpty(password)) {

        RequestDispatcher rd = request.getRequestDispatcher("/index.html");
        rd.forward(request, response);

    } else {
        System.out.println(Username + password);
        UserManager uMgr = new UserManager();
        User user = uMgr.loginUser(Username, password);
        if (user == null) {
            RequestDispatcher rd = request.getRequestDispatcher("/login.jsp");
            rd.forward(request, response);
        } else {

            if (user.isIsAdmin() == TRUE) {
                Cookie loginCookie = new Cookie("ADMIN", Username);
                //setting cookie to expiry in 30 mins
                loginCookie.setMaxAge(30*60);
                response.addCookie(loginCookie);
                request.getSession(true).setAttribute(SESSION_ADMIN, user);

                RequestDispatcher rd = request.getRequestDispatcher("index.jsp");
                rd.forward(request, response);


            } else {
                RequestDispatcher rd = request.getRequestDispatcher("/login.jsp");
                rd.forward(request, response);
            }
        }
    }

}

// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
/**
 * Handles the HTTP <code>GET</code> method.
 *
 * @param request servlet request
 * @param response servlet response
 * @throws ServletException if a servlet-specific error occurs
 * @throws IOException if an I/O error occurs
 */
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    processRequest(request, response);
}

/**
 * Handles the HTTP <code>POST</code> method.
 *
 * @param request servlet request
 * @param response servlet response
 * @throws ServletException if a servlet-specific error occurs
 * @throws IOException if an I/O error occurs
 */
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    processRequest(request, response);
}

/**
 * Returns a short description of the servlet.
 *
 * @return a String containing servlet description
 */
@Override
public String getServletInfo() {
    return "Short description";
}// </editor-fold>

}

在index.jsp页面上，我有一段代码要在开始正文标记之后运行:

<jsp:forward page="CookieServlet"/>

这是 CookieServlet:

public class CookieServlet extends HttpServlet {

/**
 * Processes requests for both HTTP <code>GET</code> and <code>POST</code>
 * methods.
 *
 * @param request servlet request
 * @param response servlet response
 * @throws ServletException if a servlet-specific error occurs
 * @throws IOException if an I/O error occurs
 */
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    String userName = null;
    Cookie[] cookies = request.getCookies();
    if(cookies !=null){
    for(Cookie cookie : cookies){
        if(cookie.getName().equals("ADMIN")) userName = cookie.getValue();
    }
    }
    if(userName == null) response.sendRedirect("login.jsp");
}

// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
/**
 * Handles the HTTP <code>GET</code> method.
 *
 * @param request servlet request
 * @param response servlet response
 * @throws ServletException if a servlet-specific error occurs
 * @throws IOException if an I/O error occurs
 */
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    processRequest(request, response);
}

/**
 * Handles the HTTP <code>POST</code> method.
 *
 * @param request servlet request
 * @param response servlet response
 * @throws ServletException if a servlet-specific error occurs
 * @throws IOException if an I/O error occurs
 */
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    processRequest(request, response);
}

/**
 * Returns a short description of the servlet.
 *
 * @return a String containing servlet description
 */
@Override
public String getServletInfo() {
    return "Short description";
}// </editor-fold>

}

登录代码有效，它为我创建了 cookie，检查 cookie 的 cookieservlet 也检查了 cookie，但没有任何 HTML 显示在带有 <jsp:forward page="CookieServlet"/> 的任何页面上。在里面。有什么问题的想法吗？

Answer 1

当您转发时，您会从一页转到另一页。当然，新页面上的信息与旧页面上的信息是不同的。如果您导航到某个页面并且仍然显示旧页面，这将是一个错误。