final HelloServiceAsync service = HelloServiceAsync.Util.getInstance();
public void onModuleLoad()
{
User user = new User();
final Label l = new Label( "GWT says : " + user.sayHello() );
RootPanel.get().add( l );
Button b = new Button( "click me !" );
RootPanel.get().add( b );
b.addClickHandler( new ClickHandler()