java中runnable

去年年底，我正在運(yùn)行預(yù)定的任務(wù)來監(jiān)視Neo4j集群，而我遇到的問題之一是有時(shí)會(huì)退出監(jiān)視。

最終我意識(shí)到這是因?yàn)镽untimeException被拋出到Runnable方法中，而我沒有處理它。 以下代碼演示了該問題：

import java.util.ArrayList; import java.util.List; import java.util.concurrent.*;public class RunnableBlog {public static void main(String[] args) throws ExecutionException, InterruptedException {ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor();executor.scheduleAtFixedRate(new Runnable() {@Overridepublic void run() {System.out.println(Thread.currentThread().getName() + " -> " + System.currentTimeMillis());throw new RuntimeException("game over");}}, 0, 1000, TimeUnit.MILLISECONDS).get();System.out.println("exit");executor.shutdown();} }

如果運(yùn)行該代碼，我們將看到RuntimeException，但是執(zhí)行器不會(huì)退出，因?yàn)榫€程在沒有通知的情況下就死了：

Exception in thread "main" pool-1-thread-1 -> 1391212558074 java.util.concurrent.ExecutionException: java.lang.RuntimeException: game overat java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:252)at java.util.concurrent.FutureTask.get(FutureTask.java:111)at RunnableBlog.main(RunnableBlog.java:11)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.lang.reflect.Method.invoke(Method.java:601)at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120) Caused by: java.lang.RuntimeException: game overat RunnableBlog$1.run(RunnableBlog.java:16)at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:351)at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:178)at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:178)at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)at java.lang.Thread.run(Thread.java:722)

當(dāng)時(shí)我最終添加了一個(gè)try catch塊并打印如下異常：

public class RunnableBlog {public static void main(String[] args) throws ExecutionException, InterruptedException {ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor();executor.scheduleAtFixedRate(new Runnable() {@Overridepublic void run() {try {System.out.println(Thread.currentThread().getName() + " -> " + System.currentTimeMillis());throw new RuntimeException("game over");} catch (RuntimeException e) {e.printStackTrace();}}}, 0, 1000, TimeUnit.MILLISECONDS).get();System.out.println("exit");executor.shutdown();} }

據(jù)我所知，這允許異常被識(shí)別，并且執(zhí)行Runnable的線程不會(huì)死亡。

java.lang.RuntimeException: game over pool-1-thread-1 -> 1391212651955at RunnableBlog$1.run(RunnableBlog.java:16)at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:351)at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:178)at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:178)at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)at java.lang.Thread.run(Thread.java:722) pool-1-thread-1 -> 1391212652956 java.lang.RuntimeException: game overat RunnableBlog$1.run(RunnableBlog.java:16)at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:351)at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:178)at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:178)at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)at java.lang.Thread.run(Thread.java:722) pool-1-thread-1 -> 1391212653955 java.lang.RuntimeException: game overat RunnableBlog$1.run(RunnableBlog.java:16)at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:351)at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:178)at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:178)at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)at java.lang.Thread.run(Thread.java:722)

這很好，使我能夠繼續(xù)監(jiān)視集群。

但是，我最近開始閱讀“ Java Concurrency in Practice ”（購(gòu)買后僅6年！），并且意識(shí)到這可能不是處理RuntimeException的正確方法。

public class RunnableBlog {public static void main(String[] args) throws ExecutionException, InterruptedException {ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor();executor.scheduleAtFixedRate(new Runnable() {@Overridepublic void run() {try {System.out.println(Thread.currentThread().getName() + " -> " + System.currentTimeMillis());throw new RuntimeException("game over");} catch (RuntimeException e) {Thread t = Thread.currentThread();t.getUncaughtExceptionHandler().uncaughtException(t, e);}}}, 0, 1000, TimeUnit.MILLISECONDS).get();System.out.println("exit");executor.shutdown();} }

我看不到這兩種方法之間的差異很大，因此如果有人可以向我解釋為什么這種方法比我以前的捕獲異常并打印堆棧跟蹤的方法更好，那將是一個(gè)很好的選擇。

參考： Java：通過Mark Needham博客博客的JCG合作伙伴 Mark Needham在Runnable中處理RuntimeException 。

翻譯自: https://www.javacodegeeks.com/2014/02/java-handling-a-runtimeexception-in-a-runnable.html

java中runnable

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