JDK异步回调

https://www.cnblogs.com/qq931399960/p/15555152.html中的实现，无论是join还是futuretask都会阻塞主线程，影响效率

JDK8出现了一个新的类CompletableFuture，可以很容易的实现异步回调，使用该类实现订餐外卖

    private static Logger logger = LoggerFactory.getLogger(OrderMealPlatformJDK8.class);

    static Boolean merchantFinish = null;
    static Boolean courierFinish = null;

    public static void main(String[] args) {
        try {
            CompletableFuture.runAsync(() -> {
                try {
                    logger.info("起锅烧油");
                    logger.info("炒菜");
                    // 5s炒菜时间
                    Thread.sleep(5000);
                    logger.info("盛饭");
                    logger.info("打包");
                    merchantFinish = true;
                } catch (Exception e) {
                    logger.error("", e);
                }
                if (courierFinish != null) {
                    sendMeal(merchantFinish, courierFinish);
                }
            });

            CompletableFuture.runAsync(() -> {
                try {
                    logger.info("抢单");
                    logger.info("规划路线");
                    // 3s赶路时间
                    Thread.sleep(3000);
                    logger.info("赶路");
                    logger.info("到店");
                    courierFinish = true;
                } catch (Exception e) {
                    logger.error("", e);
                }
                if (merchantFinish != null) {
                    sendMeal(merchantFinish, courierFinish);
                }
            });
        } catch (Exception e) {
            logger.error("", e);
        }

        logger.info("继续发布订单消息");
    }

    private static void sendMeal(boolean merchantResult, boolean courierResult) {
        if (merchantResult && courierResult) {
            logger.info("快递员开始送餐 。。。");
        } else if (merchantResult && !courierResult) {
            logger.error("外卖员车子被偷了，不能够送餐");
        } else if (!merchantResult && courierResult) {
            logger.error("商家厨师家里临时有事，请假了，做不了饭");
        } else {
            logger.error("外卖员车子被偷，商家厨师请假了 。。。 ");
        }
    }

运行结果如下：

18:24:38.425 [ForkJoinPool.commonPool-worker-1] INFO com.demo.order.OrderMealPlatformJDK8 - 起锅烧油
18:24:38.425 [main] INFO com.demo.order.OrderMealPlatformJDK8 - 继续发布订单消息
18:24:38.425 [ForkJoinPool.commonPool-worker-2] INFO com.demo.order.OrderMealPlatformJDK8 - 抢单
18:24:38.429 [ForkJoinPool.commonPool-worker-1] INFO com.demo.order.OrderMealPlatformJDK8 - 炒菜
18:24:38.429 [ForkJoinPool.commonPool-worker-2] INFO com.demo.order.OrderMealPlatformJDK8 - 规划路线

可以发现，这个结果与我们期望的不一致，并且从线程名称可以看出，使用到了默认的ForkJoinPool线程池，该线程池的关闭不受我们控制，解决以上问题，可以使用自定义线程池来处理

    private static Logger logger = LoggerFactory.getLogger(OrderMealPlatformJDK8.class);

    static Boolean merchantFinish = null;
    static Boolean courierFinish = null;

    public static void main(String[] args) {
        ThreadPoolExecutor pool = null;
        try {
            pool = new ThreadPoolExecutor(2, 2, 1000, TimeUnit.MILLISECONDS, new ArrayBlockingQueue<Runnable>(4));
            CompletableFuture.runAsync(() -> {
                try {
                    logger.info("起锅烧油");
                    logger.info("炒菜");
                    // 5s炒菜时间
                    Thread.sleep(5000);
                    logger.info("盛饭");
                    logger.info("打包");
                    merchantFinish = true;
                } catch (Exception e) {
                    logger.error("", e);
                }
                if (courierFinish != null) {
                    sendMeal(merchantFinish, courierFinish);
                }
            }, pool);

            CompletableFuture.runAsync(() -> {
                try {
                    logger.info("抢单");
                    logger.info("规划路线");
                    // 3s赶路时间
                    Thread.sleep(3000);
                    logger.info("赶路");
                    logger.info("到店");
                    courierFinish = true;
                } catch (Exception e) {
                    logger.error("", e);
                }
                if (merchantFinish != null) {
                    sendMeal(merchantFinish, courierFinish);
                }
            }, pool);
        } catch (Exception e) {
            logger.error("", e);
        } finally {
            // 模拟真实使用线程池情况,如果直接在这里执行shutdownThreadPoolGracefully方法，则main方法会阻塞（原因还不清楚）
            ThreadPoolRunnable tpr = new ThreadPoolRunnable(pool);
            Thread closePool = new Thread(tpr);
            closePool.start();
        }

        logger.info("继续发布订单消息");
    }

    private static void sendMeal(boolean merchantResult, boolean courierResult) {
        if (merchantResult && courierResult) {
            logger.info("快递员开始送餐 。。。");
        } else if (merchantResult && !courierResult) {
            logger.error("外卖员车子被偷了，不能够送餐");
        } else if (!merchantResult && courierResult) {
            logger.error("商家厨师家里临时有事，请假了，做不了饭");
        } else {
            logger.error("外卖员车子被偷，商家厨师请假了 。。。 ");
        }
    }

class ThreadPoolRunnable implements Runnable {
    private Logger logger = LoggerFactory.getLogger(ThreadPoolRunnable.class);

    private ExecutorService pool;

    public ThreadPoolRunnable(ExecutorService pool) {
        this.pool = pool;
    }

    @Override
    public void run() {
        // 如果在main方法的finally中执行该方法，则会出现main方法被阻塞（原因未知），此处模拟
        shutdownThreadPoolGracefully(pool);
    }

    private void shutdownThreadPoolGracefully(ExecutorService pool) {
        if (pool == null) {
            return;
        }
        if (!(pool instanceof ExecutorService) || pool.isTerminated()) {
            return;
        }

        try {
            // 拒绝新任务的提交，并等待所有任务有序的执行完成
            pool.shutdown();
        } catch (Exception e) {
            logger.error("", e);
        }

        try {
            // 等待60s使线程池中的任务执行完
            if (!pool.awaitTermination(60, TimeUnit.SECONDS)) {
                // 将鲜橙汁状态设置为STOP，中断所有线程，清空工作队列，取出所有未完成的任务返回给调用者
                pool.shutdownNow();

                if (!pool.awaitTermination(60, TimeUnit.SECONDS)) {
                    // 再次尝试60s
                    logger.error("线程池未正常执行结束");

                }
            }
        } catch (Exception e) {
            pool.shutdownNow();
        }

        // 仍然未关闭
        if (!pool.isTerminated()) {
            try {
                for (int i = 0; i < 1000; i++) {
                    if (pool.awaitTermination(10, TimeUnit.MILLISECONDS)) {
                        break;
                    }
                    pool.shutdownNow();
                }
            } catch (Exception e) {
                logger.error("", e);
            }
        }
    }
}

运行结果：

18:27:53.856 [main] INFO com.demo.order.OrderMealPlatformJDK8 - 继续发布订单消息
18:27:53.856 [pool-1-thread-2] INFO com.demo.order.OrderMealPlatformJDK8 - 抢单
18:27:53.856 [pool-1-thread-1] INFO com.demo.order.OrderMealPlatformJDK8 - 起锅烧油
18:27:53.859 [pool-1-thread-2] INFO com.demo.order.OrderMealPlatformJDK8 - 规划路线
18:27:53.859 [pool-1-thread-1] INFO com.demo.order.OrderMealPlatformJDK8 - 炒菜
18:27:56.860 [pool-1-thread-2] INFO com.demo.order.OrderMealPlatformJDK8 - 赶路
18:27:56.860 [pool-1-thread-2] INFO com.demo.order.OrderMealPlatformJDK8 - 到店
18:27:58.860 [pool-1-thread-1] INFO com.demo.order.OrderMealPlatformJDK8 - 盛饭
18:27:58.860 [pool-1-thread-1] INFO com.demo.order.OrderMealPlatformJDK8 - 打包
18:27:58.860 [pool-1-thread-1] INFO com.demo.order.OrderMealPlatformJDK8 - 快递员开始送餐 。。。