Fake a GWT Synchronous RPC call

Question

First of all, I know that doing a synchronous call is \"wrong\", and know that \"is not possible\".

But, in a situation a lot complex (i dont know how to explain), i

Answer 1

GWT calls XMLHttpRequest.open() whith true as its third parameter which means the call will be asynchronous. I solved a similar need for testing purposes just forcing this third parameter to be always false:

private static native void fakeXMLHttpRequestOpen() /*-{
   var proxied = $wnd.XMLHttpRequest.prototype.open;

   (function() {
       $wnd.XMLHttpRequest.prototype.open =
           function() {
                arguments[2] = false;
                return proxied.apply(this, [].slice.call(arguments));
            };
        })();
}-*/;

After invoking fakeXMLHttpRequestOpen(), any further use of XMLHttpRequest will act synchronously. For instance:

remoteSvc.getResult(new AsyncCallback() {
    @Override
    public void onSuccess(String result) {
        GWT.log("Service called!");
    }

    @Override
    public void onFailure(Throwable caught) {
        GWT.log("Service failed...");
    }
}

GWT.log("Last message");

will allways render:

Service called!
Last message

See https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/open for XMLHttpRequest.open() specification.