[melted]

Much as I dislike inheritance, "annotating a POJO" is even worse. How do you debug it if things go wrong?

[sk5t]

Same as any other code--via debug step-through, or logging, centered on the code that processes the annotations. It's actually much saner than heaps of "marker interfaces" and is readily testable.

[agentgt]

Annotated methods are also much easier (to debug) than a ton of callbacks and in theory have less GC stress.