submit方法将不会调用onNext FLOW STREAM API JAVA

Question

我正在学习Java中的FLOW Stream API，目前正在基于oracle community上的示例创建一个示例。问题在于，我看不到预期的输出，而只是看到打印在onSubscribe方法内部的SUBSCRIBING字符串。我已经检查并在StackOverflow上找到了submissionpublisher-on-submit-not-invoking-onnext-of-subscriber，但是由于我已经在调用request(Long N)而无法使用。

import java.util.concurrent.Flow;

public class Computer<T> implements Flow.Subscriber<T> {

    private Flow.Subscription subscription;

    @Override
    public void onSubscribe(Flow.Subscription subscription) {
        this.subscription = subscription;
        System.out.println("SUBSCRIBING");
        this.subscription.request(1);
    }

    @Override
    public void onNext(T item) {
        System.out.println(String.format("Got %s", item.toString()));
        this.subscription.request(1);
    }

    @Override
    public void onError(Throwable throwable) {
        throwable.printStackTrace();
    }

    @Override
    public void onComplete() {
        System.out.println("DONE");
    }

}

-

import java.util.List;
import java.util.concurrent.SubmissionPublisher;

public class Sensor {

    public static void main(String[] args) {
        SubmissionPublisher<String> submissionPublisher = new SubmissionPublisher<>();
        Computer<String> subscriber = new Computer<>();
        submissionPublisher.subscribe(subscriber);

        List<String> items = List.of("1.25", "1.224", "1.55");
        items.forEach(submissionPublisher::submit);
        submissionPublisher.close();
    }

}

我刚看到：

SUBSCRIBING

为什么不调用onNext方法？

Answer 1

您没有将ScheduledExecutorService传递给Publisher，它基本上是一个ExecutorService，可以安排任务在延迟后运行或在每次执行之间以固定的时间间隔重复执行。

import java.util.List;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.SubmissionPublisher;

public class Sensor {

    public static void main(String[] args) {
        ScheduledExecutorService executor = Executors.newScheduledThreadPool(Runtime.getRuntime().availableProcessors());
        SubmissionPublisher<String> submissionPublisher = new SubmissionPublisher<>(executor, 5);
        Computer<String> subscriber = new Computer<>();
        submissionPublisher.subscribe(subscriber);

        List<String> items = List.of("1.25", "1.224", "1.55");
        items.forEach(submissionPublisher::submit);
        submissionPublisher.close();
        executor.shutdown();
    }
}