How can we implement the SubmissionPublisher class in Java 9?

Since Java 9, we can create Reactive Streams by introducing four core interfaces: Publisher, Subscriber, Subscription, Processor, and one concrete class: SubmissionPublisher that implements the Publisher interface. Each interface plays a different role, corresponding to the principles of Reactive Streams. We can use the submit() method of SubmissionPublisher class to publish the provided item to each subscriber.

Syntax

<strong>public class SubmissionPublisher<T> extends Object implements Flow.Publisher<T>, AutoCloseable</strong>

In the below example, we can implement the SubmissionPublisher class

Example

import java.util.concurrent.Flow.Subscriber;
import java.util.concurrent.Flow.Subscription;
import java.util.concurrent.SubmissionPublisher;

class MySubscriber<T> implements <strong>Subscriber<T></strong> {
   private <strong>Subscription </strong>subscription;
   private String name;
   public MySubscriber(String name) {
      this.name = name;
   }
   <strong>@Override</strong>
   public void <strong>onComplete()</strong> {
      System.out.println(name + ": onComplete");
   }
   <strong>@Override</strong>
   public void <strong>onError</strong>(Throwable t) {
      System.out.println(name + ": onError");
      t.printStackTrace();
   }
  <strong> @Override</strong>
   public void <strong>onNext</strong>(T msg) {
      System.out.println(name + ": " + msg.toString() + " received in onNext");
      subscription.<strong>request</strong>(1);
   }
   <strong>@Override</strong>
   public void <strong>onSubscribe</strong>(Subscription subscription) {
      System.out.println(name + ": onSubscribe");
      this.subscription = subscription;
      subscription.<strong>request</strong>(1);
   }
}

<strong>// Main class</strong>
public class FlowTest {
   public static void main(String args[]) {
      <strong>SubmissionPublisher<String></strong> publisher = new <strong>SubmissionPublisher</strong><>();
      MySubscriber<String> subscriber = new MySubscriber<>("Mine");
      MySubscriber<String> subscriberYours = new MySubscriber<>("Yours");
      MySubscriber<String> subscriberHis = new MySubscriber<>("His");
      MySubscriber<String> subscriberHers = new MySubscriber<>("Her");

      publisher.<strong>subscribe</strong>(subscriber);
      publisher.<strong>subscribe</strong>(subscriberYours);
      publisher.<strong>subscribe</strong>(subscriberHis);
      publisher.<strong>subscribe</strong>(subscriberHers);

      publisher.<strong>submit</strong>("One");
      publisher.<strong>submit</strong>("Two");
      publisher.<strong>submit</strong>("Three");
      publisher.<strong>submit</strong>("Four");
      publisher.<strong>submit</strong>("Five");

      try {
         Thread.sleep(1000);
      } catch(InterruptedException e) {
         e.printStackTrace();
      }
      publisher.close();
   }
}

Output

<strong>Yours: onSubscribe
His: onSubscribe
Mine: onSubscribe
His: One received in onNext
Yours: One received in onNext
Mine: One received in onNext
Yours: Two received in onNext
His: Two received in onNext
Yours: Three received in onNext
Mine: Two received in onNext
Yours: Four received in onNext
His: Three received in onNext
Yours: Five received in onNext
Mine: Three received in onNext
Her: onSubscribe
His: Four received in onNext
Her: One received in onNext
Mine: Four received in onNext
Her: Two received in onNext
His: Five received in onNext
Her: Three received in onNext
Mine: Five received in onNext
Her: Four received in onNext
Her: Five received in onNext
Yours: onComplete
His: onComplete
Mine: onComplete
Her: onComplete</strong>