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:

  • Field Details

    • 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 Details

    • 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 Details

    • 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