code: protected void fireVetoableChange(PropertyChangeEvent event) throws PropertyVetoException {
      if (isEventDispatchEnabled()) {
        Assert.notNull(event, "The PropertyChangeEvent cannot be null!");
        if (vetoableChangeSupport.hasListeners(event.getPropertyName())) {
          vetoableChangeSupport.fireVetoableChange(event);
        }
      }
    }
docs: Notifies all VetoableChangeListeners of a property change event occurring on this Bean.  The change to
  the property may potentially be vetoed by one of the VetoableChangeListeners listening to property changes
  on this Bean, resulting in preventing the value of the property to change.
  
  @param event the PropertyChangeEvent indicating the property who's value is changing.
  @throws NullPointerException if the PropertyChangeEvent is null.
  @throws PropertyVetoException if the property change is vetoed by a VetoableChangeListener listening to
  property changes on this Bean.
  @see java.beans.PropertyChangeEvent
  @see java.beans.VetoableChangeListener
  @see java.beans.VetoableChangeSupport#fireVetoableChange(java.beans.PropertyChangeEvent)
  @see java.beans.VetoableChangeSupport#hasListeners(String)