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
com.jgoodies.binding.list.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
java.util.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.ExtendedPropertyChangeSupport(Object,boolean) .
By default all calls to #firePropertyChange will then
check the identity, not the equality. Second, you can invoke
ExtendedPropertyChangeSupport.firePropertyChange(PropertyChangeEvent,boolean) or
ExtendedPropertyChangeSupport.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.
author:
Mattias Neuling
author:
Karsten Lentzsch
version:
$Revision: 1.8 $
See Also: PropertyChangeSupport
See Also: PropertyChangeEvent
See Also: PropertyChangeListener
See Also: Object.equals(Object)
See Also: java.util.List.equals(Object) | 