java - 如何安全地关闭 GenericKeyedObjectPool？

Question

我的应用程序中有一个GenericKeyedObjectPool。我可以使用该close方法将其关闭，但是我应该如何等待客户端将每个借用的对象返回（并且池销毁）池中？

我需要类似的东西ExecutorService.awaitTermination。

Answer 1

GenericKeyedObjectPool为具有所需awaitTermination方法的包装器创建一个包装器。如果池已关闭并且每个对象都已返回（= 当前从该池借用的实例总数为零），您可以检查close和调用并减少锁存器。returnObject

public final class ListenablePool<K, V> {

    private final GenericKeyedObjectPool<K, V> delegate;

    private final CountDownLatch closeLatch = new CountDownLatch(1);

    private final AtomicBoolean closed = new AtomicBoolean();

    public ListenablePool(final KeyedPoolableObjectFactory<K, V> factory) {
        this.delegate = new GenericKeyedObjectPool<K, V>(factory);
    }

    public V borrowObject(final K key) throws Exception {
        return delegate.borrowObject(key);
    }

    public void returnObject(final K key, final V obj) throws Exception {
        try {
            delegate.returnObject(key, obj);
        } finally {
            countDownIfRequired();
        }
    }

    private void countDownIfRequired() {
        if (closed.get() && delegate.getNumActive() == 0) {
            closeLatch.countDown();
        }
    }

    public void close() throws Exception {
        try {
            delegate.close();
        } finally {
            closed.set(true);
            countDownIfRequired();
        }
    }

    public void awaitTermination() throws InterruptedException {
        closeLatch.await();
    }

    public void awaitTermination(final long timeout, final TimeUnit unit) 
            throws InterruptedException {
        closeLatch.await(timeout, unit);
    }

    public int getNumActive() {
        return delegate.getNumActive();
    }

    // other delegate methods
}

Answer 2

关闭它应该是安全的，而无需等待所有对象返回。

来自GenericKeyedObjectPool.html#close()的文档：

关闭池。池关闭后，borrowObject() 将失败并出现 IllegalStateException，但 returnObject(Object) 和 invalidateObject(Object) 将继续工作，返回的对象在返回时被销毁。