Jersey Rest API 立即返回，漫长的任务继续

Question

我的项目中有一个要求，用户调用 REST API - POST 操作来执行长时间等待的任务，现在我们不想让用户等待，而是希望立即通知用户说“任务已接受”，并在后台触发另一个线程来执行长任务。

我已经尝试了以下代码，但是当 API 返回其他线程时，不会记录任何消息或执行任何任务。我在这里错过了什么。

@POST
@Path("/longtask")
@Consumes(MediaType.APPLICATION_JSON)
public Response longTask() {
    LOGGER.info("longTask started by Thread: "+Thread.currentThread().getName());
    executor.submit(
            new Runnable() {
                @Override
                public void run() {
                    new AsyncService().longTask();
                }
            });       
    LOGGER.info("longTask completed by Thread: "+Thread.currentThread().getName());
    return Response.ok(new MyResponse<>("Task Accepted")).build();
}

异步服务

public class AsyncService {

    /**
     *
     */
    public void longTask(){
        LOGGER.info("AsyncService - longTask() Started: "+Thread.currentThread().getName());
        try{
            //Tried thenAcceptAsync as well
            CompletableFuture.supplyAsync(new MyAsyncSupplier()).thenAccept(new MyAsyncConsumer());
        }finally{
            LOGGER.info("AsyncService - longTask() Completed: "+Thread.currentThread().getName());
        }

    }   

}

MyAsyncSupplier() 和 MyAsyncConsumer() 是一些调用数据库并执行长时间等待任务的任务。 MyAsyncSupplier() 和 MyAsyncConsumer() 下的记录器不会打印。我仅使用示例 java 项目和 main() 方法尝试了相同的操作，并且发生了同样的情况。主要完成 System.out 的那一刻不会打印。

[744832b5-deed-4043-11-111] [myproject] 2018-10-08 18:19:16,836 [http-nio-8080-exec-31] INFO  mypackage.MyResource - longTask started by Thread: http-nio-8080-exec-31
[744832b5-deed-4043-11-111] [myproject] 2018-10-08 18:19:16,836 [http-nio-8080-exec-31] INFO  mypackage.MyResource - longTask completed by Thread: http-nio-8080-exec-31
[] [] 2018-10-08 18:19:16,837 [pool-64-thread-1] INFO  mypackage.AsyncService - AsyncService - longTask() Started: pool-64-thread-1
[744832b5-deed-4043-11-11] [myproject] 2018-10-08 18:19:16,844 [http-nio-8080-exec-31] DEBUG mypackage.InitializationResponseFilter - Media Type set to : application/json 

我怎样才能让这个任务继续？

CompletableFuture.supplyAsync(new MyAsyncSupplier()).thenAccept(new MyAsyncConsumer());

更新 1：

由于 MyAsyncSupplier 和 MyAsyncConsumer 类存在一些对象分配问题，上述代码无法正常工作。我进一步调试了代​​码并修复了它的工作原理。

更新 2：

实际上不需要执行者提交。

@POST
@Path("/longtask")
@Consumes(MediaType.APPLICATION_JSON)
public Response longTask() {
    LOGGER.info("longTask started by Thread: "+Thread.currentThread().getName());
    new AsyncService().longTask();
    LOGGER.info("longTask completed by Thread: "+Thread.currentThread().getName());
    return Response.ok(new MyResponse<>("Task Accepted")).build();
}

Answer 1

我认为您发布的代码很好并且可以按预期工作。也许您对 MyAsyncSupplier 和 MyAsyncSupplier 的实现是错误的。这是我的实现，试一试。

public class FunFun {
    ExecutorService executor = Executors.newFixedThreadPool(2);

    public static void main(String[] args) {
        FunFun f = new FunFun();
        f.longTask();
        f.shutdown();
//        Scanner scanner = new Scanner(System.in); changed to use shutdown.
//        scanner.nextLine();
//        System.exit(0);
    }

    public void shutdown() {
        executor.shutdown();
    }

    public String longTask() {
        System.out.println("longTask started by Thread: "+Thread.currentThread().getName());
        executor.submit(
                new Runnable() {
                    @Override
                    public void run() {
                        new AsyncService().longTask();
                    }
                });
        System.out.println("longTask completed by Thread: "+Thread.currentThread().getName());
        return "Task Accepted";
    }

    public class AsyncService {
        public void longTask(){
            System.out.println("AsyncService - longTask() Started: "+Thread.currentThread().getName());
            try{
                //Tried thenAcceptAsync as well
                CompletableFuture.supplyAsync(new MyAsyncSupplier()).   thenAcceptAsync(new MyAsyncConsumer());
            }finally{
                System.out.println("AsyncService - longTask() Completed: "+Thread.currentThread().getName());
            }
        }
    }

    public class MyAsyncSupplier implements Supplier<String>{

        @Override
        public String get() {
            System.out.println("Supplying Food");
            return "Food";
        }

    }

    public class MyAsyncConsumer implements Consumer<String>{

        @Override
        public void accept(String t) {
            System.out.println("Nom Nom " + t);
        }
    }
}

输出：

longTask started by Thread: main
longTask completed by Thread: main
AsyncService - longTask() Started: pool-1-thread-1
Supplying Food
Nom Nom Food
AsyncService - longTask() Completed: pool-1-thread-1