Why is onSubmitComplete() not executed after submitting FormPanel? - servlets

Question

I have a form for submitting credit card information data:
<g:FormPanel ui:field="creditCardForm" action="/app/create-credit-card" method="post">
<g:HTML>
<input data-braintree-name="number" value="4111111111111111"/>
<input data-braintree-name="cvv" value="100"/>
<input data-braintree-name="expiration_date" value="10/20"/>
<input data-braintree-name="postal_code" value="94107"/>
<input data-braintree-name="cardholder_name" value="John Smith"/>
</g:HTML>
</g:FormPanel>
But for some reason the SubmitCompleteHandler does not come into action when the POST is done:
this.creditCardForm.addSubmitHandler(new SubmitHandler() {
#Override
public void onSubmit(SubmitEvent event) {
LOGGER.fine("onSubmit()");
}
});
this.creditCardForm.addSubmitCompleteHandler(new SubmitCompleteHandler() {
#Override
public void onSubmitComplete(SubmitCompleteEvent event) {
LOGGER.fine("complete ..");
LOGGER.fine("Submit result: " + event.getResults());
}
});
The Servlet resturns just a String and writes some debug messages:
public class CreateCreditCardServlet extends HttpServlet implements Servlet {
private final static Logger LOGGER = Logger.getLogger(CreateCreditCardServlet.class.getName());
#Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, java.io.IOException { LOGGER.debug("#########################################################");
LOGGER.debug("doPost");
LOGGER.debug("#########################################################");
resp.getOutputStream().println("This is servlet response");
}
}
I see the response coming in the developer tool but why is the handler not getting called?

Answer 1

From the FormPanel documentation:
The back-end server is expected to respond with a content-type of
'text/html', meaning that the text returned will be treated as HTML.
If any other content-type is specified by the server, then the result
HTML sent in the onFormSubmit event will be unpredictable across
browsers, and the onSubmitComplete event may not fire at all.
So, in the servlet you need to do something like that:
resp.setContentType("text/html")