ThreadPoolExecutor 线程池源码分析-基于jdk8

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测试demo, ThreadPoolExecutorTest:

 

public class ThreadPoolExecutorTest {
	public static void main(String[] args) throws InterruptedException {
		final boolean isFair = false;
		ArrayBlockingQueue arrayBlockingQueue = new ArrayBlockingQueue(10, isFair);
//		arrayBlockingQueue.add(new MyThreadTask(10086));
		
		final int corePoolSize = 3;
		final int maximumPoolSize = 6;
		ThreadPoolExecutor threadPool = new ThreadPoolExecutor(
				corePoolSize, maximumPoolSize,
		        1, TimeUnit.SECONDS,
		        arrayBlockingQueue,
		        new ThreadPoolExecutor.CallerRunsPolicy());
		
//		threadPool.allowCoreThreadTimeOut(true);
//		Integer result = 9;
		for (int index = 1; index <= 10; index++) {
			Thread tempNewThread = new MyThreadTask(index);
		    threadPool.execute(tempNewThread);
//			result = threadPool.submit(new MyThreadTask(i), result);
		}
	    
//	    threadPool.shutdown();
	}
}

ThreadPoolExecutor 抽出来的一些核心方法:

 

 

public class ThreadPoolExecutor extends AbstractExecutorService {

	private final BlockingQueue workQueue;
	private final ReentrantLock mainLock = new ReentrantLock();
	private final HashSet workers = new HashSet();
	
	/***
	 * 线程中真正执行的Worker线程
	 */
	private final class Worker extends AbstractQueuedSynchronizer implements Runnable {
	/** Thread this worker is running in.  Null if factory fails. */
        final Thread thread;
        /** Initial task to run.  Possibly null. */
        Runnable firstTask;
        /** Per-thread task counter */
        volatile long completedTasks;
        
		Worker(Runnable firstTask) {
			setState(-1); // inhibit interrupts until runWorker
			this.firstTask = firstTask;
			this.thread = getThreadFactory().newThread(this);
		}

		/***
		 * 代理, 执行上层的runWorker方法;
		 */
		public void run() {
			runWorker(this);
		}
	}

	/***
	 * 把firstTask 添加到核心线程, 并启动;
	 * @param firstTask
	 * @param core 是否是核心线程
	 * @return
	 */
	private boolean addWorker(Runnable firstTask, boolean core) {
		boolean workerStarted = false;
		boolean workerAdded = false;
		Worker w = null;
		try {
			w = new Worker(firstTask);
			final Thread t = w.thread;
			if (t != null) {
				int rs = runStateOf(ctl.get());
				if (rs < SHUTDOWN || (rs == SHUTDOWN && firstTask == null)) {
					workers.add(w);
					int s = workers.size();
					if (s > largestPoolSize)
						largestPoolSize = s;
					workerAdded = true;
				}
				if (workerAdded) {
					t.start();
					workerStarted = true;
				}
			}
		} finally {
			if (!workerStarted)
				addWorkerFailed(w);
		}
		return workerStarted;
	}

	/***
	 * 从 workQueue 的线程等待队列中获取线程(后面准备执行);
	 * @return
	 */
	private Runnable getTask() {
		boolean timedOut = false; // Did the last poll() time out?
		for (;;) {
			try {
				Runnable r = timed ? workQueue.poll(keepAliveTime, TimeUnit.NANOSECONDS) : workQueue.take();
				if (r != null)
					return r;
				timedOut = true;
			} catch (InterruptedException retry) {
				timedOut = false;
			}
		}
	}

	/***
	 * 运行Worker线程; 
	 * 
	 * while (task != null || (task = getTask()) != null) 
	 * 第一次判断是当前的核心线程;
	 * 第二个判断是核心线程第一次执行完毕, 则从workQueue中获取线程继续执行;
	 * 
	 * task.run();
	 * 直接调用的run方法(外层已经有worker的线程包装起的)
	 */
	final void runWorker(Worker w) {
		Thread wt = Thread.currentThread();
		Runnable task = w.firstTask;
		w.firstTask = null;
		w.unlock(); // allow interrupts
		boolean completedAbruptly = true;
		try {
			while (task != null || (task = getTask()) != null) {
				w.lock();
				// If pool is stopping, ensure thread is interrupted;
				// if not, ensure thread is not interrupted. This
				// requires a recheck in second case to deal with
				// shutdownNow race while clearing interrupt
				if ((runStateAtLeast(ctl.get(), STOP) || (Thread.interrupted() && runStateAtLeast(ctl.get(), STOP)))
						&& !wt.isInterrupted())
					wt.interrupt();
				try {
					beforeExecute(wt, task);
					Throwable thrown = null;
					try {
						task.run();
					} catch (RuntimeException x) {
						thrown = x;
						throw x;
					} catch (Error x) {
						thrown = x;
						throw x;
					} catch (Throwable x) {
						thrown = x;
						throw new Error(x);
					} finally {
						afterExecute(task, thrown);
					}
				} finally {
					task = null;
					w.completedTasks++;
					w.unlock();
				}
			}
			completedAbruptly = false;
		} finally {
			processWorkerExit(w, completedAbruptly);
		}
	}

	/***
	 * 执行, 线程池执行线程的总入口
	 * @param command
	 */
	public void execute(Runnable command) {
		int c = ctl.get();
		// 核心线程执行
		if (workerCountOf(c) < corePoolSize) {
			if (addWorker(command, true))
				return;
			c = ctl.get();
		}
		// 核心已经多了, 添加到 workQueue
		if (isRunning(c) && workQueue.offer(command)) {
			int recheck = ctl.get();
			if (!isRunning(recheck) && remove(command))
				reject(command);
			else if (workerCountOf(recheck) == 0)
				addWorker(null, false);
		} else if (!addWorker(command, false))
			reject(command);
	}

	/**
	 * 其中一个拒绝策略
	 */
	public static class CallerRunsPolicy implements RejectedExecutionHandler {
		public CallerRunsPolicy() {
		}
		public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
			if (!e.isShutdown()) {
				r.run();
			}
		}
	}
}