The get started page is not that long, and you should be able to kill it in a few hours. At the minimum you get http requests routed to methods and restful json parsed for you automatically. If you want, you can add optional configuration, metrics, healthcheck, logging, db access, views etc.
In my case the Java backend exposes RESTful models via JSON which are consumed by a rails app using Her[0] a great gem that is what ActiveResource should have been. It wires up to Jersey quite easily.
However Spring using JSON as configuration format would be awesome :)
You can use annotation based configuration (meaning Java classes with annotations like @Configuration, @EnableWebMvc etc..) for > 90% of the configuration cases:
http://blog.springsource.org/2011/06/10/spring-3-1-m2-config...
Though, now that I've gotten into the annotation way I like it the most.
:)