Akka并发编程——第五节：Actor模型（四）

本节主要内容：
1. 停止Actor

1. 停止Actor

（1）通过ActorSystem.shutdown方法停止全部 Actor的执行

/*
*停止Actor:ActorSystem.shutdown方法
*/
object Example_10 extends App{
  import akka.actor.Actor
  import akka.actor.ActorSystem
  import akka.actor.Props

  class FirstActor extends Actor with ActorLogging{

    var child:ActorRef = context.actorOf(Props[MyActor], name = "myActor")
    def receive = {
      //向MyActor发送消息
      case x => child ! x;log.info("received "+x)
    }
    override def postStop(): Unit = {
      log.info("postStop In FirstActor")
    }
  }

  class MyActor extends Actor with ActorLogging{
    def receive = {
      case "test" => log.info("received test");
      case _      => log.info("received unknown message");
    }
    override def postStop(): Unit = {
      log.info("postStop In MyActor")
    }
  }
  val system = ActorSystem("MyActorSystem")
  val systemLog=system.log

  //创建FirstActor对象
  val firstactor = system.actorOf(Props[FirstActor], name = "firstActor")

  systemLog.info("准备向firstactor发送消息")
  //向firstactor发送消息
  firstactor!"test"
  firstactor! 123
  //关闭ActorSystem，停止全部Acotr执行
  system.shutdown()
}

代码执行结果：

[INFO] [04/02/2016 21:51:34.440] [main] [ActorSystem(MyActorSystem)] 准备向firstactor发送消息
[INFO] [04/02/2016 21:51:34.441] [MyActorSystem-akka.actor.default-dispatcher-4] [akka://MyActorSystem/user/firstActor/myActor] received test
[INFO] [04/02/2016 21:51:34.441] [MyActorSystem-akka.actor.default-dispatcher-2] [akka://MyActorSystem/user/firstActor] received test
[INFO] [04/02/2016 21:51:34.441] [MyActorSystem-akka.actor.default-dispatcher-2] [akka://MyActorSystem/user/firstActor] received 123
[INFO] [04/02/2016 21:51:34.441] [MyActorSystem-akka.actor.default-dispatcher-4] [akka://MyActorSystem/user/firstActor/myActor] received unknown message
[INFO] [04/02/2016 21:51:34.446] [MyActorSystem-akka.actor.default-dispatcher-4] [akka://MyActorSystem/user/firstActor/myActor] postStop In MyActor
[INFO] [04/02/2016 21:51:34.447] [MyActorSystem-akka.actor.default-dispatcher-5] [akka://MyActorSystem/user/firstActor] postStop In FirstActor

（2）通过context.stop方法停止Actor的执行

/*
*停止Actor:context.stop方法
*/
object Example_11 extends App{
  import akka.actor.Actor
  import akka.actor.ActorSystem
  import akka.actor.Props

  class FirstActor extends Actor with ActorLogging{

    var child:ActorRef = context.actorOf(Props[MyActor], name = "myActor")
    def receive = {
      case "stop"=>context.stop(child)
      case x =>{
        //向MyActor发送消息
        child ! x
        log.info("received "+x)
      }

    }
    override def postStop(): Unit = {
      log.info("postStop In FirstActor")
    }
  }

  class MyActor extends Actor with ActorLogging{
    def receive = {
      case "test" => log.info("received test");
      case _      => log.info("received unknown message");
    }
    override def postStop(): Unit = {
      log.info("postStop In MyActor")
    }
  }
  val system = ActorSystem("MyActorSystem")
  val systemLog=system.log

  //创建FirstActor对象
  val firstactor = system.actorOf(Props[FirstActor], name = "firstActor")

  systemLog.info("准备向firstactor发送消息")
  //向firstactor发送消息
  firstactor!"test"
  firstactor! 123
  firstactor!"stop"

}

代码执行结果：

[INFO] [04/02/2016 22:02:48.760] [main] [ActorSystem(MyActorSystem)] 准备向firstactor发送消息
[INFO] [04/02/2016 22:02:48.761] [MyActorSystem-akka.actor.default-dispatcher-5] [akka://MyActorSystem/user/firstActor/myActor] received test
[INFO] [04/02/2016 22:02:48.761] [MyActorSystem-akka.actor.default-dispatcher-2] [akka://MyActorSystem/user/firstActor] received test
[INFO] [04/02/2016 22:02:48.762] [MyActorSystem-akka.actor.default-dispatcher-2] [akka://MyActorSystem/user/firstActor] received 123
[INFO] [04/02/2016 22:02:48.762] [MyActorSystem-akka.actor.default-dispatcher-5] [akka://MyActorSystem/user/firstActor/myActor] received unknown message
[INFO] [04/02/2016 22:02:48.763] [MyActorSystem-akka.actor.default-dispatcher-5] [akka://MyActorSystem/user/firstActor/myActor] postStop In MyActor

代码的重点为

class FirstActor extends Actor with ActorLogging{

    var child:ActorRef = context.actorOf(Props[MyActor], name = "myActor")
    def receive = {
      case "stop"=>context.stop(child)
      case x =>{
        //向MyActor发送消息
        child ! x
        log.info("received "+x)
      }

    }
    override def postStop(): Unit = {
      log.info("postStop In FirstActor")
    }
  }

中的case “stop”=>context.stop(child)，直接通过context.stop方法停止Actor的执行。注意程序中并没有使用system.shutdown方法，因此整个程序的不会停止，例如以下图所看到的

（3）通过akka.actor.PoisonPill消息停止Actor的执行

/*
*停止Actor:使用akka.actor.PoisonPill
*/
object Example_12 extends App{
  import akka.actor.Actor
  import akka.actor.ActorSystem
  import akka.actor.Props
  import akka.actor.PoisonPill

  class FirstActor extends Actor with ActorLogging{

    var child:ActorRef = context.actorOf(Props[MyActor], name = "myActor")
    def receive = {
      //向child发送PoisonPill停止其执行
      case "stop"=>child!PoisonPill
      case x =>{
        //向MyActor发送消息
        child ! x
        log.info("received "+x)
      }

    }
    override def postStop(): Unit = {
      log.info("postStop In FirstActor")
    }
  }

  class MyActor extends Actor with ActorLogging{
    def receive = {
      case "test" => log.info("received test");
      case _      => log.info("received unknown message");
    }
    override def postStop(): Unit = {
      log.info("postStop In MyActor")
    }
  }
  val system = ActorSystem("MyActorSystem")
  val systemLog=system.log

  //创建FirstActor对象
  val firstactor = system.actorOf(Props[FirstActor], name = "firstActor")

  systemLog.info("准备向firstactor发送消息")
  //向firstactor发送消息
  firstactor!"test"
  firstactor! 123
  firstactor!"stop"

}

代码执行结果：

[INFO] [04/02/2016 22:12:09.947] [main] [ActorSystem(MyActorSystem)] 准备向firstactor发送消息
[INFO] [04/02/2016 22:12:09.947] [MyActorSystem-akka.actor.default-dispatcher-2] [akka://MyActorSystem/user/firstActor/myActor] received test
[INFO] [04/02/2016 22:12:09.947] [MyActorSystem-akka.actor.default-dispatcher-4] [akka://MyActorSystem/user/firstActor] received test
[INFO] [04/02/2016 22:12:09.947] [MyActorSystem-akka.actor.default-dispatcher-4] [akka://MyActorSystem/user/firstActor] received 123
[INFO] [04/02/2016 22:12:09.947] [MyActorSystem-akka.actor.default-dispatcher-2] [akka://MyActorSystem/user/firstActor/myActor] received unknown message
[INFO] [04/02/2016 22:12:09.951] [MyActorSystem-akka.actor.default-dispatcher-4] [akka://MyActorSystem/user/firstActor/myActor] postStop In MyActor

代码与Exampel_11中的不同之处在于

//向child发送PoisonPill停止其执行
case "stop"=>child!PoisonPill

它使用不是context.stop方法，而是向MyActor发送了PoisonPill消息，其他代码不变。

另一种gracefulStop方法能够停止Actor的执行，这部分内容等了解完Future类的作用原理之后再来讨论

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