Rest.li: A REST+JSON framework for robust, scalable service architectures
github.com
github.com
That said, it looks ok, and it does promote fairly rigorous API design, in terms of schemas, auto generating client code, and things like that - but you can apply those concepts to any protocol, it doesn't make it REST.
Why the need for all the code generation? And the huge "DATA Data Schema and Templates"? When you can control serialization thru a set of annotations in fairly standarized manner? I don't understand selling point.
Spray seems like a better option than this. If you want first-class async capability on the JVM, that's what Akka is for anyways, might as well just use it.
This seems a bit clunkier, is all.