Class VetoableChangeMulticaster

 class Thing {
   protected Color myColor = Color.red; // an example property
   protected boolean changePending; // track whether in midst of change

   // vetoable listeners:
   protected VetoableChangeMulticaster vetoers =
     new VetoableChangeMulticaster(this);

   // Possibly also some ordinary listeners:
   protected PropertyChangeMulticaster listeners =
     new PropertyChangeMulticaster(this);

   // registration methods, including:
   void addVetoer(VetoableChangeListener l) {
     // Use the `ifAbsent' version to avoid duplicate notifications
     vetoers.addVetoableChangeListenerIfAbsent(l);
   }
   
   public synchronized Color getColor() { // accessor
     return myColor;
   }

   // Simple transactional control for vetos

   public void setColor(int newColor) throws PropertyVetoException {
     Color oldColor = prepareSetColor(newColor);
    
     try {
       vetoers.fireVetoableChange("color", oldColor, newColor);
       commitColor(newColor);
       listeners.firePropertyChange("color", oldColor, newColor);
     }
     catch(PropertyVetoException ex) {
       abortSetColor();
       throw ex;
     }
   }

   // Called on entry to proposed vetoable change from setColor.
   // Throws exception if there is already another change in progress.
   // Returns current color
   synchronized int prepareSetColor(Color c) throws PropertyVetoException {
     // only support one transaction at a time
     if (changePending) 
       throw new PropertyVetoException("Concurrent modification");
       // (Could alternatively wait out other transactions via
       // a wait/notify construction based on changePending.)

     // perhaps some other screenings, like:
     else if (c == null) 
       throw new PropertyVetoException("Cannot change color to Null");
     else {
       changePending = true;
       return myColor;
     }
   }

   synchronized void commitColor(Color newColor) { 
     myColor = newColor;
     changePending = false;
   }

   synchronized void abortSetColor() {
     changePending = false;
   }

 }
 

HashMap for managing listeners for specific properties. Maps property names to VetoableChangeMulticaster objects.

Serial:

The array of listeners. Copied on each update

The object to be provided as the "source" for any generated events.

Serial:

Constructs a VetoableChangeMulticaster object.

Parameters: sourceBean The bean to be given as the source for any events.

Throws: NullPointerException if sourceBean is null

Add a VetoableChangeListener to the listener list. The listener is registered for all properties. If the listener is added multiple times, it will receive multiple change notifications upon any fireVetoableChange.

Parameters: listener The VetoableChangeListener to be added

Add a VetoableChangeListener for a specific property. The listener will be invoked only when a call on fireVetoableChange names that specific property. However, if a listener is registered both for all properties and a specific property, it will receive multiple notifications upon changes to that property.

Parameters: propertyName The name of the property to listen on. listener The VetoableChangeListener to be added

Throws: NullPointerException If listener is null

Add a PropertyChangeListener to the listener list if it is not already present. The listener is registered for all properties. The operation maintains Set semantics: If the listener is already registered, the operation has no effect.

Parameters: listener The PropertyChangeListener to be added

Throws: NullPointerException If listener is null

Add a VetoableChangeListener for a specific property, if it is not already registered. The listener will be invoked only when a call on fireVetoableChange names that specific property.

Parameters: propertyName The name of the property to listen on. listener The VetoableChangeListener to be added

Throws: NullPointerException If listener is null

Report a vetoable property update to any registered listeners. Notifications are sent serially (although in no particular order) to the list of listeners, aborting if one throws PropertyVetoException. Upon this exception, fire a new event reverting this change to all listeners that have already been notified (ignoring any further vetos), suppress notifications to all other listeners, and then rethrow the PropertyVetoException.

No event is fired if old and new are equal non-null.

Parameters: propertyName The programmatic name of the property that was changed. oldValue The old value of the property. newValue The new value of the property.

Throws: PropertyVetoException if a recipient wishes the property change to be rolled back.

Report a vetoable property update to any registered listeners. Notifications are sent serially (although in no particular order) to the list of listeners, aborting if one throws PropertyVetoException. Upon this exception, fire a new event reverting this change to all listeners that have already been notified (ignoring any further vetos), suppress notifications to all other listeners, and then rethrow the PropertyVetoException.

No event is fired if old and new are equal.

This is merely a convenience wrapper around the more general fireVetoableChange method that takes Object values.

Parameters: propertyName The programmatic name of the property that was changed. oldValue The old value of the property. newValue The new value of the property.

Throws: PropertyVetoException if the recipient wishes the property change to be rolled back.

Report a vetoable property update to any registered listeners. Notifications are sent serially (although in no particular order) to the list of listeners, aborting if one throws PropertyVetoException. Upon this exception, fire a new event reverting this change to all listeners that have already been notified (ignoring any further vetos), suppress notifications to all other listeners, and then rethrow the PropertyVetoException.

No event is fired if old and new are equal.

This is merely a convenience wrapper around the more general fireVetoableChange method that takes Object values.

Parameters: propertyName The programmatic name of the property that was changed. oldValue The old value of the property. newValue The new value of the property.

Throws: PropertyVetoException if the recipient wishes the property change to be rolled back.

Report a vetoable property update to any registered listeners. Notifications are sent serially (although in no particular order) to the list of listeners, aborting if one throws PropertyVetoException. Upon this exception, fire a new event reverting this change to all listeners that have already been notified (ignoring any further vetos), suppress notifications to all other listeners, and then rethrow the PropertyVetoException.

No event is fired if old and new are equal and non-null. equal and non-null.

Parameters: evt The PropertyChangeEvent object.

Throws: PropertyVetoException if the recipient wishes the property change to be rolled back.

Return the child associated with property, or null if no such

Check if there are any listeners for a specific property. If propertyName is null, return whether there are any listeners at all.

Parameters: propertyName the property name.

Returns: true if there are one or more listeners for the given property

Helper method to relay evt to all listeners. Called by all public fireVetoableChange methods.

Remove an occurrence of a VetoableChangeListener from the listener list. It removes at most one occurrence of the given listener. If the listener was added multiple times it must be removed mulitple times. This removes a VetoableChangeListener that was registered for all properties, and has no effect if registered for only one or more specified properties.

Parameters: listener The VetoableChangeListener to be removed

Remove a VetoableChangeListener for a specific property. Affects only the given property. If the listener is also registered for all properties, then it will continue to be registered for them.

Parameters: propertyName The name of the property that was listened on. listener The VetoableChangeListener to be removed