EDU.oswego.cs.dl.util.concurrent
Class PropertyChangeMulticaster

java.lang.Object
  EDU.oswego.cs.dl.util.concurrent.PropertyChangeMulticaster

All Implemented Interfaces:

Serializable

public class PropertyChangeMulticaster

extends Object

implements Serializable

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. ]

See Also:

Serialized Form

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(PropertyChangeEvent evt) Fire an existing PropertyChangeEvent to any registered listeners.
void	firePropertyChange(String propertyName, boolean oldValue, boolean newValue) Report a boolean 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, Object oldValue, Object newValue) Report a bound property update 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.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

listeners

protected transient PropertyChangeListener[] listeners

The array of listeners. Copied on each update

source

protected final Object source

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

children

protected HashMap children

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

Constructor Detail

PropertyChangeMulticaster

public PropertyChangeMulticaster(Object sourceBean)

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

getChild

protected PropertyChangeMulticaster getChild(String propertyName)

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

addPropertyChangeListener

public void addPropertyChangeListener(PropertyChangeListener listener)

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

addPropertyChangeListenerIfAbsent

public void addPropertyChangeListenerIfAbsent(PropertyChangeListener listener)

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

removePropertyChangeListener

public void removePropertyChangeListener(PropertyChangeListener listener)

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

addPropertyChangeListener

public void addPropertyChangeListener(String propertyName,
                                      PropertyChangeListener listener)

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

public void addPropertyChangeListenerIfAbsent(String propertyName,
                                              PropertyChangeListener listener)

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

removePropertyChangeListener

public void removePropertyChangeListener(String propertyName,
                                         PropertyChangeListener listener)

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

multicast

protected void multicast(PropertyChangeEvent evt)

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

firePropertyChange

public void firePropertyChange(String propertyName,
                               Object oldValue,
                               Object newValue)

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

public void firePropertyChange(String propertyName,
                               int oldValue,
                               int newValue)

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

public void firePropertyChange(String propertyName,
                               boolean oldValue,
                               boolean newValue)

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

public void firePropertyChange(PropertyChangeEvent evt)

Fire an existing PropertyChangeEvent to any registered listeners. No event is fired if the given event's old and new values are equal and non-null.

Parameters:

evt - The PropertyChangeEvent object.

hasListeners

public boolean hasListeners(String propertyName)

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