Personally, I would use dropwizard. Spark's key point seems to be avoiding annotation based constructs.

Compare (Spark):

  public class HelloWorld {
     public static void main(String[] args) {      
        get(new Route("/hello") {
           @Override
           public Object handle(Request request, Response response) {
              return "Hello World!";
           }
        });
     }
  } 

to (JAX-RS, which dropwizard uses)

  @Path("/hello")
  public class HelloWorld {
    @GET
    public String get() {
      return "Hello World";
    }
  }