CountDownLatch.await()挂起

Question

谁能解释一下为什么在分离的线程中执行countDown时，await方法上的CountDownLatch挂起了？这个测试永远不会结束，有趣的是，在我想执行countDown方法的地方，ThreadPoolTaskExecutor不会执行代码。我确信ThreadPoolTaskExecutor会在不同的线程中执行回调，CountDownLatch::await会被释放。

import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;

...
    private ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();

    @Test
    void nestedInitialization() {
        executor.initialize();
        var beanInitializer = new Initializer(executor);
   
        beanInitializer.initialize(() -> {
            new SomeBean().init();
        });

        sleep(150);
        assertEquals(0, executor.getThreadPoolExecutor().getQueue().size());
        assertTrue(beanInitializer.isInitializationDone());
    }

    class SomeBean {
        private AnotherBean anotherBean = new AnotherBean();

        void init() {
            anotherBean.init();
        }
    }

    class AnotherBean {
        private final Initializer initializer = new Initializer(executor);

        void init() {
            initializer.initialize(this::internalInit);
        }

        void internalInit() {
            sleep(100);
        }
    }

    public class Initializer {

        private ThreadPoolTaskExecutor bootstrapExecutor;

        private final CountDownLatch countDownLatch = new CountDownLatch(2);

        private Initializer(ThreadPoolTaskExecutor bootstrapExecutor) {
            this.bootstrapExecutor = bootstrapExecutor;
        }

        public void initialize(Runnable callback) {
            synchronized (this) {
                if (isNotInitialized()) {
                    countDownLatch.countDown(); // set 1 in latch
                    bootstrapExecutor.execute(() -> {
                        callback.run();
                        countDownLatch.countDown(); //  <-- this doesn't execute                   
                  });
                }
            }

            if (initializationStarted()) {
                try { 
                    countDownLatch.await();
                }
                catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }

        boolean isNotInitialized() { return countDownLatch.getCount() == 2; }

        boolean initializationStarted() { return countDownLatch.getCount() == 1; }

        boolean isInitializationDone() { return countDownLatch.getCount() == 0; }
    }

如果我在await方法中设置了任何超时，任务执行器中的回调将在超时和测试通过后执行……我不能理解这一点。

Answer 1

问题出在池的大小上。默认情况下，ThreadPoolTaskExecutor池中只有一个线程。我增加了corePolSize，现在他的代码可以工作了。谢谢安德烈亚斯！