Actor - Actor API

顶级Actor

import akka.actor.{ActorSystem, DeadLetter}

object AkkaActor extends App {

  import DemoActor._

  println("Hello, world!")
  val system = ActorSystem("mySystem")
  val demoActor = system.actorOf(props(42), "demoActor")
  system.eventStream.subscribe(demoActor, classOf[DeadLetter])
  println(s"demoActor created !")
  demoActor ! 88
  println(s"ready to kill demoActor's child")
  demoActor ! "kill"
}

1. 创建顶级actordemoActor
2. 订阅deadLetter
3. 发送消息 88
4. 停止 demoActor下的myActor

demoActor

import akka.actor.{Actor, ActorIdentity, ActorLogging, DeadLetter, Identify, Props, Terminated}
object DemoActor {
  /**
    * Create Props for an actor of this type.
    *
    * @param magicNumber The magic number to be passed to this actor’s constructor.
    * @return a Props for creating this actor, which can then be further configured
    *         (e.g. calling `.withDispatcher()` on it)
    */
  def props(magicNumber: Int): Props = Props(new DemoActor(magicNumber))
}

class DemoActor(magicNumber: Int) extends Actor with ActorLogging {

  import MyActor._

  println(s"magicNumber: $magicNumber")
  val myActor = context.actorOf(MyActor.props, "myActor")
  val identifyId = 1
  println(s"create myActor: ${myActor.path}")
  context.actorSelection("myActor") ! Identify(identifyId)

  context.watch(myActor)
  println("watching myActor")


  def receive = {
    case ActorIdentity(`identifyId`, Some(ref)) =>
      println(s"get actorRef: $ref")
    case ActorIdentity(`identifyId`, None) => println("not found the actorRef")
    case x: Int =>
      myActor ! Greeting(s"Vincent Guo with params $x")

    case "kill" =>
      context.stop(myActor);
      println("stopping myActor")
      myActor ! Greeting(s"after kill")
    case DeadLetter(msg, from, to) =>
      log.info("get DEAD LETTER")
      self ! msg
    case Terminated(`myActor`) => println(s"$myActor finished")
    case m => println(m)
  }

}

1. 创建子Actor myActor
2. 用actorSelection 以路径才获得actorRef
3. watch 用来监听 myActor的 Terminated 事件
4. context.stop(myActor) 停止子actor

myActor

class MyActor extends Actor {
  val log = Logging(context.system, this)

  import MyActor._

  override def preStart(): Unit = {
    println(s"${self} preStart")
  }

  override def postStop(): Unit = {
    println(s"${self} postStop")
  }

  override def preRestart(reason: Throwable, message: Option[Any]): Unit = {
    println(s"${self} preRestart")
    context.children foreach { child ⇒
      context.unwatch(child)
      context.stop(child)
    }
    println("ready to invoke postStop")
    postStop()
  }

  override def postRestart(reason: Throwable): Unit = {
    println(s"${self} postRestart")
    println(s"ready to preStart")
    preStart()
  }

  def receive = {
    case Greeting(greeter) =>
      log.info(s"I was greeted by $greeter.")
    case Goodbye => log.info("Someone said goodbye to me.")
  }
}

1. override actor生命周期
2. 获取事件并打印

Output

Hello, world!
magicNumber: 42
demoActor created !
ready to kill demoActor's child
create myActor: akka://mySystem/user/demoActor/myActor
Actor[akka://mySystem/user/demoActor/myActor#1608259142] preStart
watching myActor
stopping myActor
get actorRef: Actor[akka://mySystem/user/demoActor/myActor#1608259142]
Actor[akka://mySystem/user/demoActor/myActor#1608259142] postStop
[INFO] [04/27/2017 22:21:22.664] [mySystem-akka.actor.default-dispatcher-4] [akka://mySystem/user/demoActor/myActor] I was greeted by Vincent Guo with params 88.
[INFO] [04/27/2017 22:21:22.670] [mySystem-akka.actor.default-dispatcher-3] [akka://mySystem/user/demoActor/myActor] Message [MyActor$Greeting] from Actor[akka://mySystem/user/demoActor#751608355] to Actor[akka://mySystem/user/demoActor/myActor#1608259142] 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'.
[INFO] [04/27/2017 22:21:22.670] [mySystem-akka.actor.default-dispatcher-3] [akka://mySystem/user/demoActor] get DEAD LETTER
Greeting(after kill)
Actor[akka://mySystem/user/demoActor/myActor#1608259142] finished

1. 可以看到actor的启动和stop过程
2. 用路径获取actorRef成功
3. 死信消息拿到