java - 在主线程中运行 Flow

Question

我再次将 RxJava 与 Java 9 Flow 进行比较。我看到默认情况下 Flow 是异步的，我想知道是否有办法让它同步运行。

有时我们只想将它用于糖语法而不是用于 Nio，并拥有更同质的代码。

在 RxJava 中，默认情况下它是同步的，您可以在管道中使用 observerOn 和 subscribeOn 使其异步运行。

Flow 中是否有任何运算符使其在主线程中运行？

问候。

Answer 1

您可以按照 Flow 中的说明定义您的自定义 Publisher 用于使用同步执行。

A very simple publisher that only issues (when requested) a single TRUE item to a single subscriber. Because the subscriber receives only a single item, this class does not use buffering and ordering control.

class OneShotPublisher implements Publisher<Boolean> {
   private final ExecutorService executor = ForkJoinPool.commonPool(); // daemon-based
   private boolean subscribed; // true after first subscribe
   public synchronized void subscribe(Subscriber<? super Boolean> subscriber) {
     if (subscribed)
       subscriber.onError(new IllegalStateException()); // only one allowed
     else {
       subscribed = true;
       subscriber.onSubscribe(new OneShotSubscription(subscriber, executor));
     }
   }
   static class OneShotSubscription implements Subscription {
     private final Subscriber<? super Boolean> subscriber;
     private final ExecutorService executor;
     private Future<?> future; // to allow cancellation
     private boolean completed;
     OneShotSubscription(Subscriber<? super Boolean> subscriber,
                         ExecutorService executor) {
       this.subscriber = subscriber;
       this.executor = executor;
     }
     public synchronized void request(long n) {
       if (n != 0 && !completed) {
         completed = true;
         if (n < 0) {
           IllegalArgumentException ex = new IllegalArgumentException();
           executor.execute(() -> subscriber.onError(ex));
         } else {
           future = executor.submit(() -> {
             subscriber.onNext(Boolean.TRUE);
             subscriber.onComplete();
           });
         }
       }
     }
     public synchronized void cancel() {
       completed = true;
       if (future != null) future.cancel(false);
     }
   }
 }