Тестирование RejectedExecutionHandler в ThreadPoolExecutor

Question

Как я могу убедиться, что мой метод rejectedExecution работает

RejectedExecutionHandler() { 
     @Override 
     public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) { 
      logger.log(Level.INFO, "Name_[" + executorServiceName + "]: All threads busy, processing inline."); 
      r.run(); 
     } 
    }); 

Answer 1

Я бы лично создать ситуацию, когда мой ExecutorServiceвсегда будет отклонять задачу и проверить, что эта задача была вызвана использованием счетчик.

Так, например, мой код может быть что-то вроде этого:

// A single threaded executor service that cannot have more than 1 task in its task queue 
// such that I know that if I provide at least 3 tasks, at least 1 task will be rejected. 
// Why 3? 1 task in the queue + 1 task executed by the thread of the pool 
// = max of tasks that the pool can manage at a given time, so if I add 1 it will be 
// rejected. 
ExecutorService executor = new ThreadPoolExecutor(
    1, 1, 0L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<>(1), 
    Executors.defaultThreadFactory(), myHandler 
); 

// My Counter 
AtomicInteger counter = new AtomicInteger(); 
// Some arbitrary task that lasts long enough to make sure that at least 3 
// tasks will be submitted that will increment my counter once completed 
Runnable task =() -> { 
    try { 
     Thread.sleep(1_000L); 
    } catch (InterruptedException e) { 
     Thread.currentThread().interrupt(); 
    } finally { 
     counter.incrementAndGet(); 
    } 
}; 
try { 
    // Submit 3 tasks 
    executor.submit(task); 
    executor.submit(task); 
    executor.submit(task); 
} finally { 
    // Shutdown the pool and wait until all the submitted tasks have been executed 
    executor.shutdown(); 
    executor.awaitTermination(1L, TimeUnit.MINUTES); 
} 
// Ensure that we have 3 tasks that have been executed 
assertEquals(3, counter.get());