RESTEasy JSON Generation

[firepod]

We have the following RESTful web service response method:

@GET
@Path("/user/{uid}")
@Produces("application/json")
public Response findUser(@PathParam("uid") String userId) {

    User user = ...
    
    return Response.ok(user).build();
    
}

Does RESTEasy generate the actual JSON sting from the supplied domain object when build() is called, or does it happen after the method returns?

We're trying to identify what portion of our response time is spent on JSON generation.

Reference: Using Wildfly8.1 on Java8.

Thanks.