listener extension support

[carl harris <ce...@gmail.com>]

In GUAC-1298[1] it is noted that listener support was removed prior to the 0.9.7 release with the new extension module mechanism.

I have an application that needs tunnel-connected and tunnel-closed events and I would like to contribute listener extension support back to the project.

My approach is to 

(1) add a listeners property to the ExtensionManifest and load listener classes in the ExtensionModule

(2) create a ListenerService that is used to notify registered listener instances that were loaded by extensions

(3) inject the ListenerService into TunnelRequestService and AuthenticationService to allow listeners to be notified at the appropriate places in processing tunnel and authentication requests

Before I submit pull requests to the project I wanted to make sure that listener support was still a desired feature and that there isn’t extant work on this feature or elsewhere in the codebase that should be considered. Thanks for any feedback.

carl

[1] https://glyptodon.org/jira/browse/GUAC-1298 <https://glyptodon.org/jira/browse/GUAC-1298>