Java ExcutorService优雅关闭方式

关闭时可使用如下代码

1public static void waitUntilTerminate(final ExecutorService executorService, final int timeout) {
2        try {
3            executorService.shutdown();
4            if (!executorService.awaitTermination(timeout, TimeUnit.SECONDS)) { //超时后直接关闭
5                executorService.shutdownNow();
6            }
7        } catch (InterruptedException e) { //awaitTermination 出现中断异常也将触发关闭
8            executorService.shutdownNow();
9        }
10    }

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

1public class ShutDownUtilsTest {
2
3    private ExecutorService executorService;
4
5    @Before
6    public void init() {
7        executorService = Executors.newFixedThreadPool(1);
8    }
9
10    @Test
11    public void shutDownOKTest() {
12        ShutDownUtils.waitUntilTerminate(executorService, 1);
13
14        CommonUtils.sleep(1); //等待线程处理中断
15        Assert.assertTrue(executorService.isTerminated());
16    }
17
18    @Test
19    public void shutDownNowFailTest() {
20        executorService.execute(this::canNotStopThread);
21        ShutDownUtils.waitUntilTerminate(executorService, 0);
22
23        CommonUtils.sleep(1); //等待线程处理中断
24        Assert.assertFalse(executorService.isTerminated());
25    }
26
27    @Test
28    public void shutDownNowOKTest() {
29        executorService.execute(this::stopThread);
30        ShutDownUtils.waitUntilTerminate(executorService, 0);
31
32        CommonUtils.sleep(1); //等待线程处理中断
33        Assert.assertTrue(executorService.isTerminated());
34    }
35
36    private void canNotStopThread() {
37        for (long i = 0; i < Long.MAX_VALUE; i++) {
38        }
39    }
40
41    private void stopThread() {
42        for (long i = 0; i < Long.MAX_VALUE && !Thread.currentThread().isInterrupted(); i++) {
43        }
44    }
45}

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