Get file in a gwt

Hi all! Sorry but I have some dudes.

I want fill a ListBox (gwt) with a file txt. But some issues happen. I am doing a RequestBuilder in the widget

        Request request = builder.sendRequest(null, new RequestCallback() {
            public void onError(Request request, Throwable exception) {
                displayError("Couldn't retrieve txt");

            public void onResponseReceived(Request request,
                    Response response) {
                if (200 == response.getStatusCode()) {
                } else {
          "404!!!");    }
    } catch (RequestException e) {
        displayError("Couldn't retrieve txt");

and in a servlet the next:

protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
String rootPath = “”;
rootPath = System.getProperty(“catalina.home”);
File file = new File(rootPath+ File.separator +“file.txt”);
if (!file.exists()) {
throw new ServletException("File doesn’t exists on server: " + context);
InputStream fis = new FileInputStream(file);
String mimeType = ctx.getMimeType(file.getAbsolutePath());
resp.setContentType(mimeType != null ? mimeType
: “application/octet-stream”);
resp.setContentLength((int) file.length());
resp.setHeader(“Content-Disposition”, “attachment; filename="”
+ “one.txt” + “"”);
ServletOutputStream os = resp.getOutputStream();
byte bufferData = new byte[1024]
int read = 0;
while ((read = != -1) {
os.write(bufferData, 0, read);
System.out.println(“File downloaded at client successfully”);

But doesn’t works. Never enters in the doGet. And I test the widget (without vaadin implementations, only with the google toolkit) and works. I don’t know if I have to send a Vaddin Request in the doGet or something like that.

Thank you so much!