Java desktop DbxWebAuth with withRedirectUri NPE

Hi everyone, as I wrote in the object, I get an NPE on the line:

 HttpSession session = request.getSession(true);

Hi everyone, as I wrote in the object, I get an NPE on the line:

I'm using this code to prevent the user from manually entering the verification code into my app. from the example codes I found HttpServletRequest is not initialized (null). Do you have any examples examples? Thank you
This is the complete code

public static void main(String[] args) throws DbxException, IOException, URISyntaxException {

        HttpServletRequest request = null;
        HttpServletResponse response = null;

        DbxRequestConfig config = new DbxRequestConfig("berry120_dropbox_example"); //Client name can be whatever you like

        DbxAppInfo appInfo = new DbxAppInfo("my_code", "my_code");
        DbxWebAuth webAuth = new DbxWebAuth(config, appInfo);

        //redirect URL 
        String redirectUri = "http://localhost:8080";
        HttpSession session = request.getSession(true);

        DbxSessionStore csrfTokenStore = new DbxStandardSessionStore(session, "vj38b0mkkxnnbjg");

        DbxWebAuth.Request authRequest = DbxWebAuth.newRequestBuilder()
                .withRedirectUri(redirectUri, csrfTokenStore)
                .build();

        String authorizePageUrl = webAuth.authorize(authRequest);
        try {
            response.sendRedirect(authorizePageUrl);

        } catch (IOException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }