PropertyChangeMulticaster

This class is interoperable with java.beans.PropertyChangeSupport, but relies on a streamlined copy-on-write scheme similar to that used in CopyOnWriteArrayList. This leads to much better performance in most event-intensive programs. It also adheres to clarified semantics of add and remove operations.

Sample usage.

 class Thing {
   protected Color myColor = Color.red; // an example property

   protected PropertyChangeMulticaster listeners =
     new PropertyChangeMulticaster(this);

   // registration methods, including:
   void addListener(PropertyChangeListener l) {
     // Use the `ifAbsent' version to avoid duplicate notifications
     listeners.addPropertyChangeListenerIfAbsent(l);
   }
  
  public synchronized Color getColor() { // accessor
    return myColor;
  }

   // internal synchronized state change method; returns old value
   protected synchronized Color assignColor(Color newColor) { 
     Color oldColor = myColor;
     myColor = newColor; 
     return oldColor;
   }

   public void setColor(Color newColor) {
     // atomically change state
     Color oldColor = assignColor(newColor);
     // broadcast change notification without holding synch lock
     listeners.firePropertyChange("color", oldColor, newColor);
   }
 }

[ Introduction to this package. ]

Field Summary
protected HashMap	children HashMap for managing listeners for specific properties.
protected PropertyChangeListener[]	listeners The array of listeners.
protected Object	source The object to be provided as the "source" for any generated events.

Constructor Summary
	PropertyChangeMulticaster(Object sourceBean) Constructs a `PropertyChangeMulticaster` object.

Method Summary
void	addPropertyChangeListener(PropertyChangeListener listener) Add a VetoableChangeListener to the listener list.
void	addPropertyChangeListener(String propertyName, PropertyChangeListener listener) Add a PropertyChangeListener for a specific property.
void	addPropertyChangeListenerIfAbsent(PropertyChangeListener listener) Add a PropertyChangeListener to the listener list if it is not already present.
void	addPropertyChangeListenerIfAbsent(String propertyName, PropertyChangeListener listener) Add a PropertyChangeListener for a specific property, if it is not already registered.
void	firePropertyChange(String propertyName, Object oldValue, Object newValue) Report a bound property update to any registered listeners.
void	firePropertyChange(String propertyName, int oldValue, int newValue) Report an int bound property update to any registered listeners.
void	firePropertyChange(String propertyName, boolean oldValue, boolean newValue) Report a boolean bound property update to any registered listeners.
void	firePropertyChange(PropertyChangeEvent evt) Fire an existing PropertyChangeEvent to any registered listeners.
protected PropertyChangeMulticaster	getChild(String propertyName) Return the child associated with property, or null if no such
boolean	hasListeners(String propertyName) Check if there are any listeners for a specific property.
protected void	multicast(PropertyChangeEvent evt) Helper method to relay evt to all listeners.
void	removePropertyChangeListener(PropertyChangeListener listener) Remove a PropertyChangeListener from the listener list.
void	removePropertyChangeListener(String propertyName, PropertyChangeListener listener) Remove a PropertyChangeListener for a specific property.

PropertyChangeMulticaster

Constructs a PropertyChangeMulticaster object.

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

Throws: NullPointerException if sourceBean is null

Method Detail

addPropertyChangeListener

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 firePropertyChange

Parameters: listener The PropertyChangeListener to be added

Throws: NullPointerException If listener is null

addPropertyChangeListener

Add a PropertyChangeListener for a specific property. The listener will be invoked only when a call on firePropertyChange 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 PropertyChangeListener to be added

Throws: NullPointerException If listener is null

addPropertyChangeListenerIfAbsent

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

addPropertyChangeListenerIfAbsent

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

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

Throws: NullPointerException If listener is null

firePropertyChange

Report a bound property update to any registered listeners. No event is fired if old and new are equal and 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.

firePropertyChange

Report an int bound property update to any registered listeners. No event is fired if old and new are equal and non-null.

This is merely a convenience wrapper around the more general firePropertyChange 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.

firePropertyChange

Report a boolean bound property update to any registered listeners. No event is fired if old and new are equal and non-null.

This is merely a convenience wrapper around the more general firePropertyChange 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.

firePropertyChange

getChild

hasListeners

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

multicast

removePropertyChangeListener

Remove a PropertyChangeListener 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 PropertyChangeListener that was registered for all properties, and has no effect if registered for only one or more specified properties.

Parameters: listener The PropertyChangeListener to be removed

removePropertyChangeListener

Remove a PropertyChangeListener 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 PropertyChangeListener to be removed

Class PropertyChangeMulticaster