Scala关机挂钩永远不会运行？

斯卡拉多克sys.addShutdownHook说shutdown hooks are NOT guaranteed to be run.现在这是完全合理的,因为如果你向JVM发送一个SIGKILL,或者等同于Windows的JVM,JVM很难运行关闭挂钩.

但是添加的关闭钩子sys.addShutdownHook似乎永远不会运行,尽管那些与Runtime.getRuntime.addShutdownHookdo一起运行.

一个测试 -

scala> val t = new Thread { override def run = println("hi!") }
t: java.lang.Thread = Thread[Thread-4,5,main]

scala> Runtime.getRuntime.addShutdownHook(t)

scala> hi!
george@george-MacBook:~$ scala

(跳过启动消息)

scala> val t = new Thread { override def run = println("hi!") }
t: java.lang.Thread = Thread[Thread-4,5,main]

scala> sys.addShutdownHook(t.run _)
res0: scala.sys.ShutdownHookThread = Thread[shutdownHook1,5,main]

scala> george@george-MacBook:~$

文档说"挂钩是自动注册的:返回的值可以被忽略",所以我们不应该添加返回的线程sys.addShutdownHook (并且无论如何都会导致抛出"IllegalArgumentException:Hook之前注册的").

此外,调用addShutdownHook返回的线程上运行似乎没有做任何事情,这是可疑的.