Major Description
It would be nice if you could use the external service (i.e., ExternalLink) with a page that doesn't implement
the IExternalPage interface.
Instead, it could simply get and invoke the listener named "activateExternalPage" (or would a different name be more appropriate?)
This would make it easier for "external pages" to access the listener parameters, since (as a listener method), they can be provided as Java method parameters.
In fact, I would deprecate IExternalPage after implementing this change.