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

问题描述

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。问题是我看不到预期的输出，而只是在onSubscribe方法内部打印的 SUBSCRIBING 字符串。我已经检查并在 StackOverflow 上找到了submissionpublisher-on-submit-not-invoking-onnext-of-subscriber，但没有工作，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();
    }

}

我只是看到：

SUBSCRIBING

为什么onNext方法没有被调用？

标签： javareactive-programmingpublish-subscribejava-9

解决方案

您没有将 a 传递ScheduledExecutorService给Publisher它，它基本上是一个 ExecutorService ，它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();
    }
}

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