Question

我有一个如下所示的调度程序。它意味着每30分钟向Actor系统中的另一个actor发送一条消息。当我在eclipse IDE中为scala运行它时，此代码工作正常。但是，当我在MicroKernel中抛出此代码（使用可引导以便Microkernel可以调用它）时，我得到一个例外

java.lang.NoSuchMethodError：akka.actor.ActorSystem.dispatcher（）Lscala / concurrent / ExecutionContext; 完整的堆栈跟踪如下。我怀疑该问题可能与在此上下文中无效的“import system.dispatcher”行有关。或者调度程序试图过早地触发消息。

请帮忙......

scheduler.scala：

import akka.actor.Actor
import akka.actor.Props
import scala.concurrent.duration._
import akka.actor._
import java.sql.Timestamp;
import java.util.Date;

class Scheduler extends Actor with ActorLogging {
    import transactions._

    val system = ActorSystem("Daemon")
    import system.dispatcher
    log.info("Scheduler initializing.")
    system.scheduler.schedule( 30 milliseconds, (1000*60*30 ) milliseconds){ 
                self! updateUows(new Timestamp(new java.util.Date().getTime()))}

    def receive = {

    case updateUows(time) => { 
        log.info("updateuow to be sent.")
        context.parent!updateUows(time) 
    }
    }

}

完整的堆栈跟踪：

    [DEBUG] [07/26/2013 15:38:23.324] [Daemon-akka.actor.default-dispatcher-4] [EventStream(akka://Daemon)] Default Loggers started
Uncaught error from thread [Daemon-akka.actor.default-dispatcher-4] shutting down JVM since 'akka.jvm-exit-on-fatal-error' is enabled for ActorSystem[Daemon[ERROR] [07/26/2013
15:38:23.960] [Daemon-akka.actor.default-dispatcher-4] [ActorSystem(Daemon)] Uncaught error from thread [Daemon-akka.actor.default-dispatcher-4] shutting down JVM since 'akka
.jvm-exit-on-fatal-error' is enabled
java.lang.NoSuchMethodError: akka.actor.ActorSystem.dispatcher()Lscala/concurrent/ExecutionContext;
        at org.exactearth.PVDaemon.Scheduler$$anonfun$receive$1.applyOrElse(Scheduler.scala:25)
        at akka.actor.ActorCell.receiveMessage(ActorCell.scala:425)
        at akka.actor.ActorCell.invoke(ActorCell.scala:386)
        at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:230)
        at akka.dispatch.Mailbox.run(Mailbox.scala:212)
        at akka.dispatch.ForkJoinExecutorConfigurator$MailboxExecutionTask.exec(AbstractDispatcher.scala:506)
        at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
        at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
        at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
        at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)
]

java.lang.NoSuchMethodError: akka.actor.ActorSystem.dispatcher()Lscala/concurrent/ExecutionContext;
        at org.exactearth.PVDaemon.Scheduler$$anonfun$receive$1.applyOrElse(Scheduler.scala:25)
        at akka.actor.ActorCell.receiveMessage(ActorCell.scala:425)
        at akka.actor.ActorCell.invoke(ActorCell.scala:386)
        at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:230)
        at akka.dispatch.Mailbox.run(Mailbox.scala:212)
        at akka.dispatch.ForkJoinExecutorConfigurator$MailboxExecutionTask.exec(AbstractDispatcher.scala:506)
        at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
        at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
        at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
        at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)

Shutting down Akka...
Shutting down .............(my program)

Answer 1

它应该使用ActorSystem创建Actors，如下面的代码所示：

case object StartSched

class Test extends Actor with ActorLogging {
  def receive = {
    case StartSched =>
      context.system.scheduler.schedule( 30 milliseconds, (1000*60*30) milliseconds){
        self ! updateUows(new Timestamp(new java.util.Date().getTime()))
      }
  }
}

object Main {
  def main(args: Array[String]) {
    val sys = ActorSystem("Test")
    sys.actorOf(Props[Test])
  }
}

要在MicroKernel中启动它，您应该扩展Bootable特征并重载两个方法：startup和shutdown。 Docs

在Actor 中创建ActorSystem是一个非常糟糕的决定。

Answer 2

我的代码存在的问题是它试图创建ActorSystem。

并导入system.dispatcher是代码失败的原因。

相反，行import scala.concurrent.ExecutionContext.Implicits.global提供了要使用的默认executionContext。

感谢Alex指导我正确的方向。

case object StartSched

class Scheduler extends Actor with ActorLogging {
    import transactions._
    log.info("Scheduler initializing.")
    self!StartSched
    def receive = {
    case StartSched =>{
    import scala.concurrent.ExecutionContext.Implicits.global
    context.system.scheduler.schedule( 30 milliseconds, (1000*60*30) milliseconds){
        self ! updateUows(new Timestamp(new java.util.Date().getTime()))
      }
    }
    case updateUows(time) => { 
        log.info("updateuow to be sent.")
        context.parent!updateUows(time) 
    }
    case _=>{log.info("Don't know why we reached here.")}

}
}

Answer 3

罗兰在评论中的回答是正确的。 Scala中的java.lang.NoSuchMethodError通常意味着您使用二进制不兼容的库。

您可以在IDE项目和Microkernel应用程序中使用不同的主要Scala版本，或使用不同的主要Akka版本。

Akka Scheduler仅在MicroKernel中抛出异常，但在scclipse的eclipse IDE中工作正常

3 个答案: