NumberController.groovy

class NumberController {

    static final FiniteDuration DURATION_3_SECONDS = FiniteDuration.create(3, TimeUnit.SECONDS)
    static final TIMEOUT_3_SECONDS = Timeout.durationToTimeout(DURATION_3_SECONDS)

    ActorSystem actorSystem  //actorSystem is injected by Spring via standard Grails behavior

    def random() {
        def requestId = UUID.randomUUID().toString()

        // describe the properties of the desired actor
        def actorType = "NumberActor"
        Props props = SpringExtProvider.get(actorSystem).props(actorType)

        // ask akka to create the actor
        // use unique actor name because this will be an ephemeral, stateless actor
        // managed as a prototype bean in the spring context
        def actorName = "${actorType}-${requestId}"
        ActorRef numberActorRef = actorSystem.actorOf(props, actorName)

        def query = new NumberActor.GetRandomInteger(id: requestId, max: Integer.MAX_VALUE)
        Future<Object> futureResults = ask(numberActorRef, query, TIMEOUT_3_SECONDS)

        Promises.task {
            def randomIntegerResults = Await.result(futureResults, DURATION_3_SECONDS)
            println("randomIntegerResults: " + randomIntegerResults)

            actorSystem.stop(numberActorRef)

            render(contentType: 'application/json') {
                id = requestId
                randomInteger = randomIntegerResults
            }
        }
    }
}