Akka 指南 之「第 1 部分: Actor 的体系结构」

<!-- Maven -->
<dependency>
  <groupId>com.typesafe.akka</groupId>
  <artifactId>akka-actor_2.11</artifactId>
  <version>2.5.19</version>
</dependency>

<!-- Gradle -->
dependencies {
  compile group: 'com.typesafe.akka', name: 'akka-actor_2.11', version: '2.5.19'
}

<!-- sbt -->
libraryDependencies += "com.typesafe.akka" %% "akka-actor" % "2.5.19"

package com.example;

import akka.actor.AbstractActor;
import akka.actor.AbstractActor.Receive;
import akka.actor.ActorRef;
import akka.actor.ActorSystem;
import akka.actor.Props;

class PrintMyActorRefActor extends AbstractActor {
  static Props props() {
    return Props.create(PrintMyActorRefActor.class, PrintMyActorRefActor::new);
  }

  @Override
  public Receive createReceive() {
    return receiveBuilder()
        .matchEquals("printit", p -> {
          ActorRef secondRef = getContext().actorOf(Props.empty(), "second-actor");
          System.out.println("Second: " + secondRef);
        })
        .build();
  }
}
public class ActorHierarchyExperiments {
  public static void main(String[] args) throws java.io.IOException {
    ActorSystem system = ActorSystem.create("testSystem");

    ActorRef firstRef = system.actorOf(PrintMyActorRefActor.props(), "first-actor");
    System.out.println("First: " + firstRef);
    firstRef.tell("printit", ActorRef.noSender());

    System.out.println(">>> Press ENTER to exit <<<");
    try {
      System.in.read();
    } finally {
      system.terminate();
    }
  }
}

First: Actor[akka://testSystem/user/first-actor#1053618476]
Second: Actor[akka://testSystem/user/first-actor/second-actor#-1544706041]

class StartStopActor1 extends AbstractActor {
  static Props props() {
    return Props.create(StartStopActor1.class, StartStopActor1::new);
  }

  @Override
  public void preStart() {
    System.out.println("first started");
    getContext().actorOf(StartStopActor2.props(), "second");
  }

  @Override
  public void postStop() {
    System.out.println("first stopped");
  }

  @Override
  public Receive createReceive() {
    return receiveBuilder()
        .matchEquals("stop", s -> {
          getContext().stop(getSelf());
        })
        .build();
  }
}

class StartStopActor2 extends AbstractActor {

  static Props props() {
    return Props.create(StartStopActor2.class, StartStopActor2::new);
  }

  @Override
  public void preStart() {
    System.out.println("second started");
  }

  @Override
  public void postStop() {
    System.out.println("second stopped");
  }

  // Actor.emptyBehavior is a useful placeholder when we don't
  // want to handle any messages in the actor.
  @Override
  public Receive createReceive() {
    return receiveBuilder()
        .build();
  }
}

ActorRef first = system.actorOf(StartStopActor1.props(), "first");
first.tell("stop", ActorRef.noSender());

first started
second started
second stopped
first stopped

class SupervisingActor extends AbstractActor {
  static Props props() {
    return Props.create(SupervisingActor.class, SupervisingActor::new);
  }

  ActorRef child = getContext().actorOf(SupervisedActor.props(), "supervised-actor");

  @Override
  public Receive createReceive() {
    return receiveBuilder()
        .matchEquals("failChild", f -> {
          child.tell("fail", getSelf());
        })
        .build();
  }
}

class SupervisedActor extends AbstractActor {
  static Props props() {
    return Props.create(SupervisedActor.class, SupervisedActor::new);
  }

  @Override
  public void preStart() {
    System.out.println("supervised actor started");
  }

  @Override
  public void postStop() {
    System.out.println("supervised actor stopped");
  }

  @Override
  public Receive createReceive() {
    return receiveBuilder()
        .matchEquals("fail", f -> {
          System.out.println("supervised actor fails now");
          throw new Exception("I failed!");
        })
        .build();
  }
}

ActorRef supervisingActor = system.actorOf(SupervisingActor.props(), "supervising-actor");
supervisingActor.tell("failChild", ActorRef.noSender());

supervised actor started
supervised actor fails now
supervised actor stopped
supervised actor started
[ERROR] [03/29/2017 10:47:14.150] [testSystem-akka.actor.default-dispatcher-2] [akka://testSystem/user/supervising-actor/supervised-actor] I failed!
java.lang.Exception: I failed!
        at tutorial_1.SupervisedActor$$anonfun$receive$4.applyOrElse(ActorHierarchyExperiments.scala:57)
        at akka.actor.Actor$class.aroundReceive(Actor.scala:513)
        at tutorial_1.SupervisedActor.aroundReceive(ActorHierarchyExperiments.scala:47)
        at akka.actor.ActorCell.receiveMessage(ActorCell.scala:519)
        at akka.actor.ActorCell.invoke(ActorCell.scala:488)
        at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:257)
        at akka.dispatch.Mailbox.run(Mailbox.scala:224)
        at akka.dispatch.Mailbox.exec(Mailbox.scala:234)
        at akka.dispatch.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
        at akka.dispatch.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
        at akka.dispatch.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
        at akka.dispatch.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)