线程池相关

支持生产阻塞的线程池, 使用了阻塞生产者的方式. 把队列设为有限队列.队列满了,调用构造时传入的RejectedExecutionHandler去拒绝任务的处理

RejectedExecutionHandler中继续往有界队列中put(阻塞)来添加元素.

new RejectedExecutionHandler() {
	@Override
	public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {
		if (!executor.isShutdown()) {
			try {
				executor.getQueue().put(r);
			} catch (InterruptedException e) {
				// should not be interrupted
			}
		}
	}
};

http://ifeve.com/blocking-threadpool-executor/

 

复习一下线程池队列满了之后的拒绝策略

一复习,拉一串.

谷歌的有个库,

 

提供了一个ThreadFactoryBuilder,可以把一些复杂的参数都写在链式里面.

ThreadFactory namedThreadFactory = new ThreadFactoryBuilder().setNameFormat("ABC-Pool-%d").build();

然后创建线程池

ExecutorService pool = new ThreadPoolExecutor(

3,  //3个core

200,//200个maxPoolSize

0L,//keepAlived time

TimeUnit.MILLISECONDS,  //kepAlivedTime 单位

new LinkedBlockingQueue<Runnable>(1024), //队列, 设为有界

namedThreadFactory, //线程工厂

new ThreadPoolExecutor.AbortPolicy() //拒绝策略, 是RejectedExecutionHandler 的实现

);

其中JDK实现的拒绝策略有4种

AbortPolicy 的实现其实是抛出  throw new RejectedExecutionException("Task " + r.toString() +" rejected from " +e.toString());

DiscardPolicy 的实现是 什么都不做,-->悄悄的丢掉

DiscardOldestPolicy 的实现是, 悄悄的从队列里e.getQueue().poll();掉一个task, 然后把当前task加进去. --->悄悄的顶一个出去.

CallerRunsPolicy的实现是, 让生产者自己做.(生产线程就会阻塞)

 

线程池然后使用 pool.execute(runnable)来执行runnable task.

pool.execute(()->{  //do something  });

可以结合countDownLatch,来阻塞最后的终止.

 

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interface ExecutorService extends Executor 

 executor.execute(()->{});//是执行runnable

executorService.submit 可以submit callabel和runnable

 

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CompletableFuture.runAsync参数是一个runnable,
内部实现是:
--->
asyncRunStage(asyncPool, runnable);
--->
asyncRunStage(screenExecutor(executor), runnable);
--->
CompletableFuture<Void> d = new CompletableFuture<Void>();
executor.execute(new AsyncRun(d, f));

AsyncRun 是一个静态内部类,implements Runnable和Task系某接口
static final class AsyncRun extends ForkJoinTask<Void> implements Runnable, AsynchronousCompletionTask {

executor 是一个线程池
private static final Executor asyncPool = useCommonPool ? ForkJoinPool.commonPool() : new ThreadPerTaskExecutor();

screenExecutor(executor) 其实就是null-check
Null-checks user executor argument, and translates uses of commonPool to asyncPool in case parallelism disabled.