Paul,


A PropertyChangeListener receives PropertyChangeEvent objects which are
quite generic.

It seems to me that if the type of events that are going to be
generated is unknown, then PropertyChangeListener/PropertyChangeEvent
might be the right way.

If however, the type of events are known in advance and their number
small (number of types), then writing a specific interface (see
o.a.l.spi.LoggerEventListener, HierarchyEventListener) might be most
appropriate.

Do you know the types of events you are interested in for the plugins?

At 03:41 PM 9/5/2003 +1000, Paul Smith wrote:
Could we extend Plugins to support the concept of
PropertyChangeListeners (java.bean package stuff)?

PropertyChangeListener and associated classes are a great way of binding
objects together and being notified when certain properties change.
This allows for a very nicely decoupled design, particular in GUI's.

What I would propose to do is modify PluginSkeleton to add the following
methods:

public void addPropertyChangeListener(PropertyChangeListener l);
public void removePropertyChangeListener(PropertyChangeListener l);

For each setter property in PluginSkeleton and it's children, modify the
method to fire a PropertyChangeEvent.  Listeners can then modify
themselves based on the old/new value accordingly.

We can use the PropertyChangeSupport class to do most of the heavy
lifting.  Since Swing uses these classes extensively, they have been
optimized to ensure that if no-one is listening, as little CPU/memory as
possible is wasted.

Does anyone have any objects, or comments?

cheers,

Paul Smith


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