@Bean public Controller controller(){
  if (useQtInterface) {
    return new ControllerQtImplementation();
  }
 else {
    return new ControllerJavaFXImplementation();
  }
}

@ Bean public Controller controller ( ) { if ( useQtInterface ) { return new ControllerQtImplementation ( ) ; } else { return new ControllerJavaFXImplementation ( ) ; } }
this bean represents the ui controller
