com.jgoodies.binding.beans
Class ExtendedPropertyChangeSupport

java.lang.Object
  extended by java.beans.PropertyChangeSupport
      extended by com.jgoodies.binding.beans.ExtendedPropertyChangeSupport
All Implemented Interfaces:
java.io.Serializable

public final class ExtendedPropertyChangeSupport
extends java.beans.PropertyChangeSupport

Differs from its superclass PropertyChangeSupport in that it can check for changed values using #equals or ==. Useful if you want to ensure that a PropertyChangeEvent is fired if the old and new value are not the same but if they are equal.

The Java Bean Specification recommends to not throw a PropertyChangeEvent if the old and new value of a bound Bean property are equal (see chapter 7.4.4). This can reduce the number of events fired and helps avoid loops. Nevertheless a bound property may fire an event if the old and new value are equal.

An example for a condition where the identity check == is required and the #equals test fails is class SelectionInList. If the contained ListModel changes its value, an internal listener is removed from the old value and added to the new value. The listener must be moved from the old instance to the new instance even if these are equal. The PropertyChangeSupport doesn't fire a property change event if such a ListModel is implemented as a List. This is because instances of List are equal if and only if all list members are equal and if they are in the same sequence.

This class provides two means to fire an event if the old and new value are equal but not the same. First, you enable the identity check in constructor ExtendedPropertyChangeSupport(Object, boolean). By default all calls to #firePropertyChange will then check the identity, not the equality. Second, you can invoke firePropertyChange(PropertyChangeEvent, boolean) or firePropertyChange(String, Object, Object, boolean) and enable or disable the identity check for this call only.

TODO: (Issue #5) Use WeakReferences to refer to registered listeners.

TODO: (Issue #6) Add an optional check for valid property name when adding a listener for a specific property.

TODO: (Issue #7) Add an optional strict check for existing property names when firing a named property change.

TODO: (Issue #8) Add an option to ensure that update notifications are performed in the event dispatch thread. In case a bean is changed in a thread other than the event dispatch thread, such a feature would help complying with Swing's single thread rule.

TODO: (Issue #11) Consider adding an option that saves update notifications if 'checkIdentity' is true but the value types can be compared safely via #equals, for example Strings, Booleans and Numbers.

Version:
$Revision: 1.10 $
Author:
Mattias Neuling, Karsten Lentzsch
See Also:
PropertyChangeSupport, PropertyChangeEvent, PropertyChangeListener, Object.equals(Object), List.equals(Object), Serialized Form

Constructor Summary
ExtendedPropertyChangeSupport(java.lang.Object sourceBean)
          Constructs an ExtendedPropertyChangeSupport object.
ExtendedPropertyChangeSupport(java.lang.Object sourceBean, boolean checkIdentityDefault)
          Constructs an ExtendedPropertyChangeSupport object with the specified default test method for differences between the old and new property values.
 
Method Summary
 void firePropertyChange(java.beans.PropertyChangeEvent evt)
          Fires the specified PropertyChangeEvent to any registered listeners.
 void firePropertyChange(java.beans.PropertyChangeEvent evt, boolean checkIdentity)
          Fires an existing PropertyChangeEvent to any registered listeners.
 void firePropertyChange(java.lang.String propertyName, java.lang.Object oldValue, java.lang.Object newValue)
          Reports a bound property update to any registered listeners.
 void firePropertyChange(java.lang.String propertyName, java.lang.Object oldValue, java.lang.Object newValue, boolean checkIdentity)
          Reports a bound property update to any registered listeners.
 
Methods inherited from class java.beans.PropertyChangeSupport
addPropertyChangeListener, addPropertyChangeListener, fireIndexedPropertyChange, fireIndexedPropertyChange, fireIndexedPropertyChange, firePropertyChange, firePropertyChange, getPropertyChangeListeners, getPropertyChangeListeners, hasListeners, removePropertyChangeListener, removePropertyChangeListener
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

ExtendedPropertyChangeSupport

public ExtendedPropertyChangeSupport(java.lang.Object sourceBean)
Constructs an ExtendedPropertyChangeSupport object.

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

ExtendedPropertyChangeSupport

public ExtendedPropertyChangeSupport(java.lang.Object sourceBean,
                                     boolean checkIdentityDefault)
Constructs an ExtendedPropertyChangeSupport object with the specified default test method for differences between the old and new property values.

Parameters:
sourceBean - The object provided as the source for any generated events.
checkIdentityDefault - true enables the identity check by default
Method Detail

firePropertyChange

public void firePropertyChange(java.beans.PropertyChangeEvent evt)
Fires the specified PropertyChangeEvent to any registered listeners. Uses the default test (#equals vs. ==) to determine whether the event's old and new values are different. No event is fired if old and new value are the same.

Overrides:
firePropertyChange in class java.beans.PropertyChangeSupport
Parameters:
evt - The PropertyChangeEvent object.
See Also:
PropertyChangeSupport.firePropertyChange(PropertyChangeEvent)

firePropertyChange

public void firePropertyChange(java.lang.String propertyName,
                               java.lang.Object oldValue,
                               java.lang.Object newValue)
Reports a bound property update to any registered listeners. Uses the default test (#equals vs. ==) to determine whether the event's old and new values are different. No event is fired if old and new value are the same.

Overrides:
firePropertyChange in class java.beans.PropertyChangeSupport
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.
See Also:
PropertyChangeSupport.firePropertyChange(String, Object, Object)

firePropertyChange

public void firePropertyChange(java.beans.PropertyChangeEvent evt,
                               boolean checkIdentity)
Fires an existing PropertyChangeEvent to any registered listeners. The boolean parameter specifies whether differences between the old and new value are tested using == or #equals. No event is fired if old and new value are the same.

Parameters:
evt - The PropertyChangeEvent object.
checkIdentity - true to check differences using == false to use #equals.

firePropertyChange

public void firePropertyChange(java.lang.String propertyName,
                               java.lang.Object oldValue,
                               java.lang.Object newValue,
                               boolean checkIdentity)
Reports a bound property update to any registered listeners. No event is fired if the old and new value are the same. If checkIdentity is true an event is fired in all other cases. If this parameter is false, an event is fired if old and new values are not equal.

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.
checkIdentity - true to check differences using == false to use #equals.


Copyright © 2002-2008 JGoodies Karsten Lentzsch. All Rights Reserved.