How to send a message to an actor from outside in Play Framework 2?

Question

I am new to Akka and trying to write some code in Play Framework 2 in Java and use Akka. To create an actor and send a test message to it, I have:


public class Global extends GlobalSettings {

    @Override
    public void onStart(Application app) {
        final ActorRef testActor = Akka.system().actorOf(Props.create(TestActor.class), "testActor");
        testActor.tell("hi", ActorRef.noSender());
    }
}

This work perfectly fine and I see that my actor received my message, here is the code for my actor:


public class TestActor extends UntypedActor {

    @Override
    public void onReceive(Object message) throws Exception {
        if(message.toString().equals("hi")){
            System.out.println("I received a HI");
        }else{
            unhandled(message);
        }
    }
}

Very simple. However, If I try to send a message from a controller:


public static Result index() {
        final ActorRef testActor = Akka.system().actorFor("testActor");
        testActor.tell("hi", ActorRef.noSender());
        return ok(index.render("Your new application is ready."));
    }

I get this message on terminal:

[INFO] [09/20/2014 11:40:30.850] [application-akka.actor.default-dispatcher-4] [akka://application/testActor] Message [java.lang.String] from Actor[akka://application/deadLetters] to Actor[akka://application/testActor] was not delivered. [1] dead letters encountered. This logging can be turned off or adjusted with configuration settings 'akka.log-dead-letters' and 'akka.log-dead-letters-during-shutdown'.

Can someone help me with this? why the first usage works and the second one fails? Thanks

I suggest you to pass ActorRef to controller instead of using actorFor method. — Mustafa Simav

Marius Soutier Marius Soutier · Accepted Answer · 2014-09-20T20:07:43

The actorFor method requires the entire path, and your actor lives in the user space, so you have to use actorFor("/user/testActor"). Currently you are sending it to application/testActor, which would be a top-level actor in the ActorSystem itself.

By the way, actorFor is deprecated (at least in the Scala API) and replaced by actorSelection.

For more information, refer to the excellent documentation.

How to send a message to an actor from outside in Play Framework 2?

2 Answers