Tomás Denis Reyes Sánchez :
I'm learning about the FLOW Stream API in Java and I'm currently creating an example based on the one that is on oracle community. The problem is that I don't get to see the expected output but just the SUBSCRIBING string that is printed inside onSubscribe method. I already checked and found submissionpublisher-on-submit-not-invoking-onnext-of-subscriber on StackOverflow, but didn't work because I was already calling 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();
}
}
And I just get to see:
SUBSCRIBING
Why onNext method is not being called?
Tomás Denis Reyes Sánchez :
You are not passing a ScheduledExecutorService to the Publisher which is basically an ExecutorService which can schedule tasks to run after a delay or to execute repeatedly with a fixed interval of time in between each execution.
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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