vaadin: getting user logindata from external page

Question

i wrote a normal html login form, that forwards to a vaadin project, where i want to receive the username and password and check if its valid. but i have problems getting this request.

when i add a requesthandler in the init() method of my UI class, i can only get the request data after the second call of the vaadin page (because at the first call of init, the hander ist not added yet)

 @Override
protected void init(VaadinRequest vaadinRequest) {
    setContent(new MainComponent()); 
    VaadinSession.getCurrent().addRequestHandler(
            new RequestHandler() {
                @Override
                public boolean handleRequest(VaadinSession vaadinSession, VaadinRequest vaadinRequest, VaadinResponse vaadinResponse) throws IOException {
                    String username = vaadinRequest.getParameter("username");
                    return false;
                }
            });

so i tried to overwrite the VaadinServlet method doPost, but it does not get triggered. when i overwrite the methode service(HttpServletRequest request, HttpServletResponse response), this method is triggered a serval times for each request, so also not a good place to get just the userdata.

so whats the right way to solve this problem?

Answer 1

i dont't know if this is the best solution, but at least it works. maybe this helps someone.

here a short explanation what i do. i retrieve the posted username and password from the post values of my plain html login formular from another url and see if it is existing in the database. if it exists, it returns the result, otherwise the value ERROR.

i extended the VaadinServlet and overwrote the method service like this

@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    super.service(request, response);

    String username = request.getParameter("username");
    if(username != null) { // called several times, only set when username is returned, otherwise the value remains "error"
        String password = request.getParameter("password");
        this.result = getResult(username, Encrypter.encryp(password));
    }
}

and this is inside my class extended from UI

@Override
protected void init(VaadinRequest vaadinRequest) {        
    MyServlet myServlet = (MyServlet) VaadinServlet.getCurrent();
    String result = myServlet.getResult();

    if(result .equals(MyServlet.ERROR)){ // check if the result set in the servlet is valid, otherwise forward to the loginpage
        goToLogin();
        myServlet.resetResult();
        return;
    }
    myServlet.resetResult();

   ...
}