java - 提交方法不会调用 onNext FLOW STREAM API JAVA

Question

我正在学习 Java 中的 FLOW Stream API，我目前正在创建一个基于 oracle community 上的示例的示例.问题是我看不到预期的输出，而只看到打印在 onSubscribe 方法中的 SUBSCRIBING 字符串。我已经检查并找到了submissionpublisher-on-submit-not-invoking-onnext-of-subscriber在 StackOverflow 上，但没有用，因为我已经在调用 request(Long N)。

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();
    }

}

我刚刚看到:

SUBSCRIBING

为什么 onNext 方法没有被调用？

Answer 1

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

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();
    }
}