Actor 两种模式 Tell Ask
Tell 完全异步
Ask 返回 future , 可以同步 异步处理

receive  使用  sender() ! msg  发送结果
发送端 使用  ?  运算符 ，获取 future 后 进行 后续处理

import akka.actor.{Actor, ActorSystem, Props}
import akka.pattern.ask
import akka.util.Timeout

import java.util.concurrent.TimeUnit
import scala.concurrent.ExecutionContext.Implicits.global
import scala.util.{Failure, Success}

class HelloActor extends Actor {
  def receive = {
    // case "hello"  => println("hello back to you.")
    case msg: String => println("msg=" + msg + ",sender=" + sender())
                        sender() ! msg
    case _ => println("what?")
  }
}

object Hello extends App {
  // actor need an ActorSystem
  val system = ActorSystem("HelloSystem")
  // create and start the actor
  val helloActor = system.actorOf(Props[HelloActor], name = "helloActor")
  // send  messages
  helloActor ! "hello"

  implicit val timeout = Timeout(1 ,TimeUnit.SECONDS)
  // ask
  (helloActor ? "hello") .andThen{
    case Success(result) => println("ask result="+result)
    case Failure(err) => println((s"ask error: $err"))
  }

  //  使用 ?  需要 import akka.pattern.ask
  //  Future[Any]
  val future = helloActor ? "hello-ask"

  Thread.sleep(100)
  println("ask future result = "+future)

  Thread.sleep(3000)
  // shutdown the actor system
  system.terminate()
}


msg=hello,sender=Actor[akka://HelloSystem/deadLetters]
msg=tell hello,sender=Actor[akka://HelloSystem/deadLetters]

msg=hello,sender=Actor[akka://HelloSystem/temp/helloActor$a]
msg=hello-ask,sender=Actor[akka://HelloSystem/temp/helloActor$b]
msg=hello ask2,sender=Actor[akka://HelloSystem/temp/helloActor$c]


发送 tell 消息时  ， sender() 获取到 /deadLetters
发送 ask  消息时  ， sender() 获取到 /temp/helloActor$xxx

/temp/ 是系统创建的 用于 ask 模式


完整代码
https://gitee.com/dyyx/hellocode/blob/master/demo/scala/akka/akka-quickstart-scala-maven/src/main/java/com/example/dyyx/hello/Hello.scala