扩展ThreadPoolExector

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在实际开发中使用线程池时，通常我们都不会直接使用如下的方式来创建一个线程池，而是通过新建ThreadPoolExecutor对象或者继承ThreadPoolExecutor类，及配置相关属性来新建一个线程池，这样有很多好处大家都知道，有什么不太清楚的可以参照 Executor 框架小结一文。

ExecutorService executorService = Executors.newFixedThreadPool(10);ExecutorService executorService2 = Executors.newSingleThreadExecutor();ExecutorService executorService3 = Executors.newCachedThreadPool();

那么如何对我们新建的进行扩展呢？我们在这里采用的是新建一个继承ThreadPoolExecutor的类AroundThreadPool，扩展的功能是beforeExecute方法和afterExecute方法，这两个方法都是ThreadPoolExecutor类中空实现的方法，我们可以在AroundThreadPool类中重写。

protected void beforeExecute(Thread t, Runnable r) { }protected void afterExecute(Runnable r, Throwable t) { }

重写的功能主要是，对已处理的任务的计数和处理时间的监控，具体代码如下：

public class AroundThreadPool extends ThreadPoolExecutor {public AroundThreadPool(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue,RejectedExecutionHandler handler) {super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, handler);}private final ThreadLocal<Long> startTime = new ThreadLocal<Long>();private final Logger log = Logger.getLogger("AroundThreadPool");private final AtomicLong numTasks = new AtomicLong();private final AtomicLong totalTime = new AtomicLong();@Overrideprotected void beforeExecute(Thread t, Runnable r) {super.beforeExecute(t, r);log.fine(String.format("Thread %s: start %s", t, r));startTime.set(System.nanoTime());System.out.println(startTime);}@Overrideprotected void afterExecute(Runnable r, Throwable t) {long endTime = System.nanoTime();long taskTime = endTime - startTime.get();numTasks.incrementAndGet();totalTime.addAndGet(taskTime);log.fine(String.format("Thread %s: end %s, time=%dns", t, r, taskTime));super.afterExecute(r, t);System.out.println(endTime);}}

大致上我们可以对任务进行简单的监控了。

测试类的代码：

public static void main(String[] args) {ExecutorService scheduledExecutorService = new AroundThreadPool(5, 10, 60, TimeUnit.SECONDS, new LinkedBlockingDeque<>(1000),new ThreadPoolExecutor.AbortPolicy());for (int i = 0; i < 80; i++) {scheduledExecutorService.submit(new Runnable() {@Overridepublic void run() {System.out.println("hhh");}});}}

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