FULL PRODUCT VERSION :


A DESCRIPTION OF THE PROBLEM :
If the newValue of the property is null, and the oldValue of the property is null, the property has not changed. You test for .equals() but the code

        if (changeSupport == null ||
(oldValue != null && newValue != null && oldValue.equals(newValue))) {
            return;
        }
        changeSupport.firePropertyChange(propertyName, oldValue, newValue);

misses the case where newValue==oldValue==null

I cannot think of a use case where you'd want to fire a property change in this context for a property has not changed. I'm dealing with a lot of Actions extending AbstractAction, and see tons of extraneous, unnecessary property change events being fired when no property values have actually changed.

A simple fix would be to just include && oldValue == newValue as part of the if statement, ie.:

        if (changeSupport == null ||
                (oldValue != null && newValue != null && oldValue.equals(newValue)) ||
                 oldValue == newValue)
        {
            return;
        }


REPRODUCIBILITY :
This bug can be reproduced always.

CUSTOMER SUBMITTED WORKAROUND :
Override firePropertyChange in the AbstractAction subclass to implement this fix.