GWT FormPanel onSubmitComplete event not firing when downloading a file - events

Question

I created servlet to download file from a server. In GWT I created a FormPanel and I am able to download a file.
Problem is, that I want to fire an event, when the file is ready. I tried to use onSubmitComplete event, but it isn't firing.
I found a suggestion, to change ContetType to "text/html", but still no luck. I found, that the problem lies in writing to OutputStream - when commented out, event is fired.
Here is my servlet code
public void handleRequest(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html");
response.setHeader("Content-Disposition", "attachment; filename=File.xls");
HSSFWorkbook workbook = new HSSFWorkbook();
try {
workbook = fileCreator.getWorkbook();
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} catch (ParseException e) {
e.printStackTrace();
}
OutputStream out = response.getOutputStream();
workbook.write(out);
out.close();
response.setStatus(HttpServletResponse.SC_OK);
response.getWriter().print("something");
response.flushBuffer();
}
So file is downloaded successfully, but event is not triggered. Even when I just get OutputStream and close it (without writing to it), event stops working.
When I remove whole "writing-to-output-stream" code, event works like a charm.
Any suggestions?
UPDATE
Here is code for FormPanel and its handlers, meby there is a problem?
Form:
downloadFileFormPanel.setEncoding(FormPanel.ENCODING_URLENCODED);
downloadFileFormPanel.setMethod(FormPanel.METHOD_POST);
VerticalPanel panel = new VerticalPanel();
panel.setWidth(UIConstatns.SIZE_100percent);
downloadFileFormPanel.setWidget(panel);
downloadFileButton = new Button(messages.EXPORT_LIMITS());
downloadFileButton.setWidth(UIConstatns.SIZE_100percent);
downloadFileButton.addStyleName("navigation-button");
panel.add(downloadFileButton);
Handlers
private void registerExportLimitsHandler() {
registerHandler(getView().getDownloadFileButton().addClickHandler(new ClickHandler() {
#Override
public void onClick(ClickEvent event) {
getView().showLoadingDialog();
getDownloadFileForm().submit();
}
}));
}
private void registerFormSubmitCompleteHandler() {
getView().getDownloadFileForm().addSubmitCompleteHandler(new SubmitCompleteHandler() {
public void onSubmitComplete(SubmitCompleteEvent event) {
Window.alert("download complete");
getView().hideLoadingDialog();
}
});
}

Answer 1

According to the Javadoc of ServletResponse#getWriter() you can either use response.getOutputStream() or response.getWriter() to write the body of the response, but not both. Furthermore it is better to set the status code of the response before writing the body. Please try the following:
// ...
response.setStatus(HttpServletResponse.SC_OK);
OutputStream out = response.getOutputStream();
workbook.write(out);
out.flush();
out.close();
// response.getWriter().print("something");
// response.flushBuffer();

Answer 2

You did not post the line where you create your FormPanel so I'm not sure if this was your problem:
Looks like the FormPanel(String target) constructor does not work with the SubmitCompleteHandler. With the default constructor it seems to work.