如何安全关闭GenericKeyedObjectPool？

Question

我的应用程序中有一个GenericKeyedObjectPool。 我可以用close方法关闭它，但我该如何等待客户返回池（并且池会销毁）每个借用对象到池中？

我需要类似ExecutorService.awaitTermination。

Answer 1

为GenericKeyedObjectPool创建一个包装，其中包含所需的awaitTermination方法。您可以检查close和returnObject调用，并在池关闭并返回每个对象（=当前从该池中借用的实例总数为零）时递减锁存器。

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

您应该安全地关闭它，而不必等待所有的对象返回。

从GenericKeyedObjectPool.html#close()文档：

关闭池。池关闭后，borrowObject（）将失败 with IllegalStateException，但returnObject（Object）和 invalidateObject（Object）将继续工作，返回的对象 将返回销毁。