Java ExcutorService优雅关闭方式解析

关闭时可使用如下代码

public static void waitUntilTerminate(final ExecutorService executorService, final int timeout) {
   try {
     executorService.shutdown();
     if (!executorService.awaitTermination(timeout, TimeUnit.SECONDS)) { //超时后直接关闭
       executorService.shutdownNow();
     }
   } catch (InterruptedException e) { //awaitTermination 出现中断异常也将触发关闭
     executorService.shutdownNow();
   }
 }

但是实际使用中，可能会出现即使使用了shutdownNow方法，还是无法终止线程的问题，那是因为你的线程无法被中断

shutdownNow方法简单理解就是给在运行的线程发一个中断信号，如果你的线程忽略这个信号，那就无法停下来

举个例子来说明这个问题

public class ShutDownUtilsTest {

private ExecutorService executorService;

@Before
 public void init() {
   executorService = Executors.newFixedThreadPool(1);
 }

@Test
 public void shutDownOKTest() {
   ShutDownUtils.waitUntilTerminate(executorService, 1);

CommonUtils.sleep(1); //等待线程处理中断
   Assert.assertTrue(executorService.isTerminated());
 }

@Test
 public void shutDownNowFailTest() {
   executorService.execute(this::canNotStopThread);
   ShutDownUtils.waitUntilTerminate(executorService, 0);

CommonUtils.sleep(1); //等待线程处理中断
   Assert.assertFalse(executorService.isTerminated());
 }

@Test
 public void shutDownNowOKTest() {
   executorService.execute(this::stopThread);
   ShutDownUtils.waitUntilTerminate(executorService, 0);

CommonUtils.sleep(1); //等待线程处理中断
   Assert.assertTrue(executorService.isTerminated());
 }

private void canNotStopThread() {
   for (long i = 0; i < Long.MAX_VALUE; i++) {
   }
 }

private void stopThread() {
   for (long i = 0; i < Long.MAX_VALUE && !Thread.currentThread().isInterrupted(); i++) {
   }
 }
}

从上面的测试用例可以看到canNotStopThread无法被shutDownNow终止

然而stopThread可以被正常终止，因为通过Thread.currentThread().isInterrupted()在判断线程是否收到了中断信号

来源：https://www.cnblogs.com/migoo/p/11062154.html