For what its worth, I've sort of answered this question after working on some other production projects.
- Home brew: Using Spring AOP to pointcut around the method calls prior to executing API method code is one home-brew way if you have your own algorithm to implement. This ends up being pretty elegant and flexible as you can capture a lot of metadata prior to deciding what to do with the request.
- API Management Service: If you're talking about a production system and you have the budget, probably the best way to go is to delegate this to an API Management layer like Apigee or Mashery.
Advantage is that it separates the concerns so its easier to change and allows you to focus just on your API. This is especially helpful if business stakeholders are involved and you need a good UI and dictionary of terms.
Disadvantage, of course is the cost and the vendor lock in.
Hope this helps someone!