EDU.oswego.cs.dl.util.concurrent
Class PropertyChangeMulticaster
- Serializable
public class PropertyChangeMulticaster
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. ]
protected HashMap | children - HashMap for managing listeners for specific properties.
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protected PropertyChangeListener[] | listeners - The array of listeners.
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protected Object | source - The object to be provided as the "source" for any generated events.
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void | addPropertyChangeListener(PropertyChangeListener listener) - Add a VetoableChangeListener to the listener list.
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void | addPropertyChangeListener(String propertyName, PropertyChangeListener listener) - Add a PropertyChangeListener for a specific property.
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void | addPropertyChangeListenerIfAbsent(PropertyChangeListener listener) - Add a PropertyChangeListener to the listener list if it is
not already present.
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void | addPropertyChangeListenerIfAbsent(String propertyName, PropertyChangeListener listener) - Add a PropertyChangeListener for a specific property, if it is not
already registered.
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void | firePropertyChange(PropertyChangeEvent evt) - Fire an existing PropertyChangeEvent to any registered listeners.
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void | firePropertyChange(String propertyName, Object oldValue, Object newValue) - Report a bound property update to any registered listeners.
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void | firePropertyChange(String propertyName, boolean oldValue, boolean newValue) - Report a boolean bound property update to any registered listeners.
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void | firePropertyChange(String propertyName, int oldValue, int newValue) - Report an int bound property update to any registered listeners.
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protected PropertyChangeMulticaster | getChild(String propertyName) - Return the child associated with property, or null if no such
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boolean | hasListeners(String propertyName) - Check if there are any listeners for a specific property.
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protected void | multicast(PropertyChangeEvent evt) - Helper method to relay evt to all listeners.
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void | removePropertyChangeListener(PropertyChangeListener listener) - Remove a PropertyChangeListener from the listener list.
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void | removePropertyChangeListener(String propertyName, PropertyChangeListener listener) - Remove a PropertyChangeListener for a specific property.
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children
protected HashMap children
HashMap for managing listeners for specific properties.
Maps property names to PropertyChangeMulticaster objects.
listeners
protected 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.
PropertyChangeMulticaster
public PropertyChangeMulticaster(Object sourceBean)
Constructs a PropertyChangeMulticaster
object.
sourceBean
- The bean to be given as the source for any events.
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
listener
- The PropertyChangeListener to be added
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.
propertyName
- The name of the property to listen on.listener
- The PropertyChangeListener to be added
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.
listener
- The PropertyChangeListener to be added
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.
propertyName
- The name of the property to listen on.listener
- The PropertyChangeListener to be added
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.
evt
- The PropertyChangeEvent object.
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.
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.
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.
propertyName
- The programmatic name of the property
that was changed.oldValue
- The old value of the property.newValue
- The new value of the property.
getChild
protected PropertyChangeMulticaster getChild(String propertyName)
Return the child associated with property, or null if no such
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.
propertyName
- the property name.
- true if there are one or more listeners for the given property
multicast
protected void multicast(PropertyChangeEvent evt)
Helper method to relay evt to all listeners.
Called by all public firePropertyChange methods.
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.
listener
- The PropertyChangeListener to be removed
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.
propertyName
- The name of the property that was listened on.listener
- The PropertyChangeListener to be removed