Question

为什么Await.result(f, t)将重新抛出由f引发的异常，而它不会重新抛出致命错误？

是错误还是预期行为？

以下REPL序列再现了行为：

scala> import scala.concurrent.duration._
import scala.concurrent.duration._

scala> import scala.concurrent._
import scala.concurrent._

scala> val ec = scala.concurrent.ExecutionContext.global
ec: scala.concurrent.ExecutionContextExecutor = scala.concurrent.impl.ExecutionContextImpl@2d2217da

scala> Await.result(Future{throw new RuntimeException()}(ec), Duration.Inf)
java.lang.RuntimeException
    at $anonfun$1.apply(<console>:15)
    at $anonfun$1.apply(<console>:15)
    at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24)
    at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24)
    at scala.concurrent.impl.ExecutionContextImpl$$anon$3.exec(ExecutionContextImpl.scala:107)
    at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
    at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
    at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
    at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)


scala> Await.result(Future{throw new LinkageError()}(ec), Duration.Inf)
scala.NotImplementedError: an implementation is missing
    at $line28.$read$$iw$$iw$$iw$$iw$$iw$$iw$$anonfun$1.apply(<console>:15)
    at $line28.$read$$iw$$iw$$iw$$iw$$iw$$iw$$anonfun$1.apply(<console>:15)
    at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24)
    at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24)
    at scala.concurrent.impl.ExecutionContextImpl$$anon$3.exec(ExecutionContextImpl.scala:107)
    at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
    at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
    at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
    at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)
    (hanging - needs ctrl-c)

两次执行之间的区别在于第一次执行将终止执行，第二次将打印堆栈跟踪然后挂起，永远等待（虽然不确定）。

Edit1：将NotImplementedError替换为LinkageError，因为在{2.1}中修改了NotImplementedError行为，而LinkageError保持不变。

Edit2：添加＆＃34;致命＆＃34;描述问题中的错误。

Answer 1

这是因为scala.util.NonFatal（在Future的实现中使用）与NotImplementedError不匹配，导致它被视为致命的。在2.11中，这已经改变了，NotImplementedError不再是致命的。请参阅this commit。

Await.result（...）Scala 2.10中致命错误和异常处理之间的区别

1 个答案: