helloButton.addClickHandler(new ClickHandler() {
@Override
public void onClick(ClickEvent event) {
GwtActionServiceAsync service = GWT.create(GwtActionService.class);
((ServiceDefTarget) service).setServiceEntryPoint(GWT.getModuleBaseURL() + "rpc");
service.execute(new HelloAction(nameField.getText()), new AsyncCallback<HelloResponse>() {
@Override
public void onFailure(Throwable caught) {
GWT.log("Failed to send hello", caught);
}