@Override
public void addListener(InvalidationListener listener) {
if( fxInvalidationListeners == null ) {
fxInvalidationListeners = new ArrayList<InvalidationListener>();
dbInvalidationListener = new IChangeListener() {
@Override
public void handleChange(ChangeEvent event) {
for( InvalidationListener l : fxInvalidationListeners.toArray(new InvalidationListener[0]) ) {
l.invalidated(WrappedValue.this);