if(vectorLayer.getFeatureDataLoadedListeners() != null
&& vectorLayer.getFeatureDataLoadedListeners().size() > 0) {
// add a behavior to be notified when new data is loaded
VectorFeatureDataLoadedListener vectorFeatureDataLoadedListener =
new VectorFeatureDataLoadedListener(vectorLayer) {
@Override
public void handleDataLoaded(AjaxRequestTarget target, JsonArray features) {
vectorLayer.notifyFeatureDataLoadedListeners(target, features);
}