How do I conditionally serve different JSON objects from a Spring (3.1) backend? I am using Spring Security but I don't understand how I can serve different representations of an object?

I am only interested in the security logic, the other things I already have in place. 

If a user named `Sylvester` is logged in with the role `admin` then he will recieve a bigger JSON object (more data) then a `Arnold` with the role `user`. 

Do I have to use the authentication object see if the user has a particular role? Or are there some annotations or some other magic to do this?