akka创建actor时报错：IllegalArgumentException: no matching constructor found on class $iwC$$iwC$$iwC$$iwC$

在spark-shell中输入范例中的代码：

import akka.actor.Actor
import akka.actor.Props
import akka.event.Logging

class MyActor extends Actor {
  val log = Logging(context.system, this)
  def receive = {
    case "test" ⇒ log.info("received test")
    case _      ⇒ log.info("received unknown message")
  }
}

val system = ActorSystem("MySystem")
  val myActor = system.actorOf(Props[MyActor], name = "myactor")

结果总是遇到如下错误：

scala>   val myActor = system.actorOf(Props[MyActor], name = "myactor")
java.lang.IllegalArgumentException: no matching constructor found on class $iwC$$iwC$$iwC$$iwC$MyActor for arguments []
	at akka.util.Reflect$.error$1(Reflect.scala:81)
	at akka.util.Reflect$.findConstructor(Reflect.scala:93)
	at akka.actor.Props.constructor(Props.scala:194)
	at akka.actor.Props.<init>(Props.scala:213)
	at akka.actor.Props$.apply(Props.scala:69)
	at $iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC.<init>(<console>:24)

百思不得其解！最后终于找到了原因：不能采用内嵌类作为actor类！！！！spark-shell里面的类会被认为是内嵌类，为了避免以上错误，需要单独写类文件。

stackoverflow里面是这么解释的：

Take this example:

class A{
  class B{}
}

I can do new A, but new B will return an error. I have to do:

val a = new A
val b = new a.B

That's why akka failed to create this actor.