Java Akka 调度 API 抛出 MissingMethodException

Question

Java 8(好吧，Groovy)在这里使用 Akka com.typesafe.akka:akka-actor_2.11:2.5.4。我正在尝试创建一个参与者 (AppMaster)，它创建/拥有/管理另一个参与者 (StateChecker)，并计划发送此 StateChecker每 4 秒发送一条 CheckState 消息:

class CheckState {}

class StateChecker extends AbstractActor {
  // For this question, it really doesn't matter what this actor does
}

class AppMaster extends AbstractActor {
    ActorRef stateChecker

    @Override
    Receive createReceive() {
      receiveBuilder()
            .match(Init, { message ->
              stateChecker = context.actorOf(Props.create(StateChecker, "yes", 20), "state-checker")

              FiniteDuration startDur = Duration.Zero()

              FiniteDuration freqDur = Duration.create(4000, TimeUnit.MILLISECONDS)
              CheckState checkState = new CheckState()
              ExecutionContextExecutor executor = context.system().dispatcher()

              context.system().scheduler().schedule(startDur, freqDur, stateChecker, checkState,
                executor)
            })
        .build()
    }
}

当我运行此程序时，出现以下异常:

groovy.lang.MissingMethodException: No signature of method: akka.actor.LightArrayRevolverScheduler.schedule() is applicable for argument types: (scala.concurrent.duration.FiniteDuration, scala.concurrent.duration.FiniteDuration, akka.actor.LocalActorRef, com.me.myapp.messages.CheckState, akka.dispatch.Dispatcher) values: [0 days, 4000 milliseconds, Actor[akka://myapp/user/myapp-master/o1-keeper#-1837899613], ...]
Possible solutions: schedule(scala.concurrent.duration.FiniteDuration, scala.concurrent.duration.FiniteDuration, java.lang.Runnable, scala.concurrent.ExecutionContext), schedule(scala.concurrent.duration.FiniteDuration, scala.concurrent.duration.FiniteDuration, scala.Function0, scala.concurrent.ExecutionContext), schedule(scala.concurrent.duration.FiniteDuration, scala.concurrent.duration.FiniteDuration, akka.actor.ActorRef, java.lang.Object, scala.concurrent.ExecutionContext, akka.actor.ActorRef)
    at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.unwrap(ScriptBytecodeAdapter.java:58)
    at org.codehaus.groovy.runtime.callsite.PojoMetaClassSite.call(PojoMetaClassSite.java:49)

我添加了日志语句，并且在调度期间抛出异常:

context.system().scheduler().schedule(startDur, freqDur, stateChecker, checkState,
  executor)

知道我需要做什么来解决这个问题吗？由于这是我在使用 Akka 的 Java API 时遇到的问题，因此我确实需要通过 Java API 获得答案。

Answer 1

问题在于您传递给 schedule() 方法的参数与该方法的任何重载版本都不匹配。您可以在 JavaDoc 中看到 schedule() 的重载版本的签名。 .

您尝试使用的版本如下 method :

Cancellable schedule(scala.concurrent.duration.FiniteDuration initialDelay,
                     scala.concurrent.duration.FiniteDuration interval,
                     ActorRef receiver,
                     java.lang.Object message,
                     scala.concurrent.ExecutionContext executor,
                     ActorRef sender)

您缺少最后一个参数，它是一个 ActorRef，被指定为计划消息的发件人。如果 StateChecker 不关心谁向其发送 CheckState 消息，那么最简单的解决方法是传入 null 作为最后一个参数:

context.system()
       .scheduler()
       .schedule(startDur, freqDur, stateChecker, checkState, executor, null)
                                                                     // ^