DataHandler should not cache a default command map in currentCommandMap.
The reason is that if the client has never called
DataHandler.setCommandMap, or has called setCommandMap(null), then there's
no semantically defined point at which a default commmand map is cached,
and hence calling CommandMap.setDefaultCommandMap will no longer affect a
particular DataHandler instance.

Suggested fix: Instead of calling private synchronized void
initDefaultCommandMap(), and then access currentCommandMap, use this
whereever a CommandMap is needed:

private synchronized CommandMap getCommandMap() {
if (currentCommandMap != null)
return currentCommandMap;
else
return CommandMap.getDefaultCommandMap();

}

There's really no performance penalty for not caching it, since if no
changes have been made, it's been cached by CommandMap anyway. The issue is ensuring consistancy of behavior between DataHandler instances when the default commmand map has been swapped.