chapter08_线程池的使用_4_扩展ThreadPoolExecutor

最新推荐文章于 2025-10-31 11:29:39 发布

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本文介绍如何通过扩展ThreadPoolExecutor类中的hook方法，实现对线程执行前后及线程池关闭时的操作。具体展示了TimingThreadPool类的实现，该类记录了每个任务的执行时间和平均执行时间。

ThreadPoolExecutor类中提供了几个hook方法

  class ThreadPoolExecutor {

      ...

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

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

      protected void terminated() { }

      ...
  }

所以这几个方法可以自己扩展

beforeExecute是在执行任务前被调用；aferExecute在执行任务后被调用（无论是否抛出异常都会执行）；terminated在线程池关闭时调用

  public class TimingThreadPool extends ThreadPoolExecutor {

      public TimingThreadPool() {

          super(1, 1, 0L, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>());
      }

      private final ThreadLocal<Long> startTime = new ThreadLocal<Long>();
      private final Logger log = Logger.getLogger("TimingThreadPool");
      private final AtomicLong numTasks = new AtomicLong();
      private final AtomicLong totalTime = new AtomicLong();

      protected void beforeExecute(Thread t, Runnable r) {

          super.beforeExecute(t, r);
          log.fine(String.format("Thread %s: start %s", t, r));
          startTime.set(System.nanoTime());
      }

      protected void afterExecute(Runnable r, Throwable t) {

          try {
              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));
          } finally {
              super.afterExecute(r, t);
          }
      }

      protected void terminated() {

          try {
              log.info(String.format("Terminated: avg time=%dns", totalTime.get() / numTasks.get()));
          } finally {
              super.terminated();
          }
      }
  }