通用对象池

Question

我正在研究GenericObjectPool，把Cipher放在池中，这样它就可以重用了。

GenericObjectPool<Cipher> pool;

CipherFactory factory = new CipherFactory(); 
this.pool = new GenericObjectPool<Cipher>(factory);
pool.setMaxTotal(10);
pool.setBlockWhenExhausted(true);
pool.setMaxWaitMillis(30 * 1000);

CipherFactory

public class CipherFactory extends BasePooledObjectFactory<Cipher> {

    private boolean running = false;

    @Override
    public Cipher create() throws Exception {
        return Cipher.getInstance("DESede/CBC/NoPadding");
    }

    @Override
    public PooledObject<Cipher> wrap(Cipher arg0) {
        return new DefaultPooledObject<Cipher>(arg0);
    }

    @Override
    public boolean validateObject(PooledObject<Cipher> p) {
        //Ensures that the instance is safe to be returned by the pool
        return true;
    }

    @Override
    public void destroyObject(PooledObject<Cipher> p) {
        //Destroys an instance no longer needed by the pool. 
        System.out.println("destroying");
    }

    @Override
    public void activateObject(PooledObject<Cipher> p) throws Exception { //Reinitialize an instance to be returned by the pool

        setRunning(true);
    }

    @Override
    public void passivateObject(PooledObject<Cipher> p) throws Exception {   // reset the object after the object returns to the pool

        setRunning(false);
    }

    public void setRunning(boolean running) {

        this.running = running;
    }
//    
}

这就是我如何在示例类中实现ObjectPool的方法。

public Key aKey(byte[] tmkByte) throws Exception {

        Cipher cipher = null;
        cipher = pool.borrowObject(); //get the object from the pool
        try {
            System.out.println("****************** After borrow ****************");
            printPool();
            cipher.init(Cipher.DECRYPT_MODE, mkkey, algParamSpec);
            byte[] de = cipher.doFinal(tmkByte);
            SecretKey tmk = new SecretKeySpec(de, "DESede");
            return tmk;
        } catch (Exception e) {
            pool.invalidateObject(cipher);
            cipher = null;
        } finally {
            if (null != cipher) {
                pool.returnObject(cipher);
                System.out.println("****************** After return ****************");
                printPool();
            }
        }
        return (Key) cipher;
    }

printPool

public void printPool() {
        System.out.println("Pool for cipher with instances DESede/CBC/NoPadding");
        System.out.println("Active [" + pool.getNumActive() + "]"); //Return the number of instances currently borrowed from this pool
        System.out.println("Idle [" + pool.getNumIdle() + "]"); //The number of instances currently idle in this pool
        System.out.println("Total Created [" + pool.getCreatedCount() + "]");      
    }

有趣的部分来了。当我运行我的应用程序时，我得到了以下输出：

****************** After borrow ****************
Pool for cipher with instances DESede/CBC/NoPadding
Active [1]
Idle [0]
Waiter [0]
Total Created [1]
****************** After return ****************
Pool for cipher with instances DESede/CBC/NoPadding
Active [0]
Idle [1]
Waiter [0]
Total Created [1]

如果我在没有returnObject到pool的情况下运行应用程序3次

****************** After borrow ****************
Pool for cipher with instances DESede/CBC/NoPadding
Active [1]
Idle [0]
Waiter [0]
Total Created [1]

****************** After return ****************
Pool for cipher with instances DESede/CBC/NoPadding
Active [1]
Idle [0]
Waiter [0]
Total Created [1]

****************** After borrow ****************
Pool for cipher with instances DESede/CBC/NoPadding
Active [2]
Idle [0]
Waiter [0]
Total Created [2]

****************** After return ****************
Pool for cipher with instances DESede/CBC/NoPadding
Active [2]
Idle [0]
Waiter [0]
Total Created [2]

****************** After borrow ****************
Pool for cipher with instances DESede/CBC/NoPadding
Active [3]
Idle [0]
Waiter [0]
Total Created [3]

****************** After return ****************
Pool for cipher with instances DESede/CBC/NoPadding
Active [3]
Idle [0]
Waiter [0]
Total Created [3]

如果我跑了10多次，我就会如愿以偿：

java.util.NoSuchElementException:等待空闲对象的超时

基于输出和代码，我是否正确地实现？

Answer 1

看起来不错，除了: activateObject/passivateObject方法:我没有看到运行变量的任何用法？除此之外，您也不需要在这个方法中做任何事情，它将被调用，在返回对象之前，我不认为这是密码实例所需要的，不是吗？

但是我要回答的原因是:我很肯定你不会因为密码实例使用池而获得任何好处。池的管理、同步、代码维护和附加库将使用更多的资源。

一般的规则是，“按定义”：代码越多意味着性能越低。当然，这并不是完全正确的--我想说的是:如果你想提高性能，你必须在你的改变之前和之后进行测量。不仅仅是millis，还有cpu、内存、gc、io等等。你必须确定的是，你的改变确实取得了进步，而不是相反。

希望能帮上忙..。