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Akka/Scala example source code file (SupervisedAsk.java)

This example Akka source code file (SupervisedAsk.java) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Akka and Scala source code examples by using tags.

All credit for the original source code belongs to akka.io; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Akka tags/keywords

actor, actorref, akka, askparam, asktimeout, concurrent, duration, exception, object, override, pattern, props, throwable, time, timeout, untypedactor

The SupervisedAsk.java Akka example source code

package docs.pattern;

import java.util.concurrent.TimeoutException;

import scala.concurrent.Future;
import scala.concurrent.duration.Duration;

import akka.actor.Actor;
import akka.actor.ActorKilledException;
import akka.actor.ActorRef;
import akka.actor.ActorRefFactory;
import akka.actor.Cancellable;
import akka.actor.OneForOneStrategy;
import akka.actor.Props;
import akka.actor.Scheduler;
import akka.actor.Status;
import akka.actor.SupervisorStrategy;
import akka.actor.SupervisorStrategy.Directive;
import akka.actor.Terminated;
import akka.actor.UntypedActor;
import akka.japi.Function;
import akka.pattern.Patterns;
import akka.util.Timeout;

public class SupervisedAsk {

  private static class AskParam {
    Props props;
    Object message;
    Timeout timeout;

    AskParam(Props props, Object message, Timeout timeout) {
      this.props = props;
      this.message = message;
      this.timeout = timeout;
    }
  }

  private static class AskTimeout {
  }

  public static class AskSupervisorCreator extends UntypedActor {

    @Override
    public void onReceive(Object message) throws Exception {
      if (message instanceof AskParam) {
        ActorRef supervisor = getContext().actorOf(
            Props.create(AskSupervisor.class));
        supervisor.forward(message, getContext());
      } else {
        unhandled(message);
      }
    }
  }

  public static class AskSupervisor extends UntypedActor {
    private ActorRef targetActor;
    private ActorRef caller;
    private AskParam askParam;
    private Cancellable timeoutMessage;

    @Override
    public SupervisorStrategy supervisorStrategy() {
      return new OneForOneStrategy(0, Duration.Zero(),
          new Function<Throwable, Directive>() {
            public Directive apply(Throwable cause) {
              caller.tell(new Status.Failure(cause), self());
              return SupervisorStrategy.stop();
            }
          });
    }

    @Override
    public void onReceive(Object message) throws Exception {
      if (message instanceof AskParam) {
        askParam = (AskParam) message;
        caller = getSender();
        targetActor = getContext().actorOf(askParam.props);
        getContext().watch(targetActor);
        targetActor.forward(askParam.message, getContext());
        Scheduler scheduler = getContext().system().scheduler();
        timeoutMessage = scheduler.scheduleOnce(askParam.timeout.duration(),
            self(), new AskTimeout(), context().dispatcher(), null);
      } else if (message instanceof Terminated) {
        Throwable ex = new ActorKilledException("Target actor terminated.");
        caller.tell(new Status.Failure(ex), self());
        timeoutMessage.cancel();
        getContext().stop(self());
      } else if (message instanceof AskTimeout) {
        Throwable ex = new TimeoutException("Target actor timed out after "
            + askParam.timeout.toString());
        caller.tell(new Status.Failure(ex), self());
        getContext().stop(self());
      } else
        unhandled(message);
    }
  }

  public static Future<Object> askOf(ActorRef supervisorCreator, Props props,
      Object message, Timeout timeout) {
    AskParam param = new AskParam(props, message, timeout);
    return Patterns.ask(supervisorCreator, param, timeout);
  }

  synchronized public static ActorRef createSupervisorCreator(
      ActorRefFactory factory) {
    return factory.actorOf(Props.create(AskSupervisorCreator.class));
  }
}

Other Akka source code examples

Here is a short list of links related to this Akka SupervisedAsk.java source code file:

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