Used to clean up a desktop.
There are two ways to use this interface.
First: add the listener at the run time
Call {@link Desktop#addListener} to register it.
Second: use configuration
- Specify a class that implements this interface in WEB-INF/zk.xml as a listener.
- Then, each time ZK loader is destroying a desktop, an instnace of the specified class is instantiated and {@link #cleanup} is called.
@author tomyeh