Implementation independent subscribe / handler implementation

[davidsowerby]

Currently only the publishing side of an event bus is independent of the implementation.

Assuming we want to provide for MBassador and Vert.x as a minimum, with a preference to include Guava as well, to achieve the same independence for the subscribe element, the following needs to be addressed:

• MBassador and Guava use different annotations to identify handlers. Vert.x does not seem to use annotations at all
• Some specialised annotations are used (for example @enveloped in MBassador)
• Filtering is applied through annotations in MBassador
• Sync / Async handling is selected through MBassador @handler attributes
• Dead message handling

Whether it is worth the effort is debatable ... but as a first step maybe the MBassador annotations could be re-purposed when used in a Vert.x environment

[davidsowerby]

Take a look at MBassador Feature SyncPubSub and its use of MetaDataReader