在Java 9中，我们如何实现Subscriber接口？

Java 9 通过引入一些接口来支持创建反应式流： Publisher、Subscriber、Subscription和实现Publisher 接口的SubmissionPublisher 类。每个接口可以根据反应式流的原则扮演不同的角色。

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我们可以使用Subscriber 接口订阅由publisher发布的数据。我们需要实现Subscriber 接口并为抽象方法提供实现。

Flow.Subscriber接口的方法：

• onComplete()：当Publisher对象完成其角色时调用此方法。
• onError()：当Publisher出现问题并通知Subscriber时调用此方法。
• onNext()：当Publisher有新信息要通知给所有Subscribers时调用此方法。
• onSubscribe()：当Publisher添加Subscriber时调用此方法。

示例

import java.util.concurrent.Flow;
import java.util.concurrent.SubmissionPublisher;
import java.util.stream.IntStream;

public class SubscriberImplTest {
   public static class Subscriber implements Flow.Subscriber {
      private Flow.Subscription subscription;
      private boolean isDone;
      
      @Override
      public void onSubscribe(Flow.Subscription subscription) {
         System.out.println("Subscribed");
         this.subscription = subscription;
         this.subscription.request(1);
      }
      @Override
      public void onNext(Integer item) {
         System.out.println("Processing " + item);
         this.subscription.request(1);
      }
      @Override
      public void onError(Throwable throwable) {
         throwable.printStackTrace();
      }
      @Override
      public void onComplete() {
         System.out.println("Processing done");
         isDone = true;
      }
   }
   public static void main(String args[]) throws InterruptedException {
      SubmissionPublisher publisher = new SubmissionPublisher<>();
      Subscriber subscriber = new Subscriber();
      publisher.subscribe(subscriber);
      IntStream intData = IntStream.rangeClosed(1, 10);
      intData.forEach(publisher::submit);
      publisher.close();
      while(!subscriber.isDone) {
         Thread.sleep(10);
      }
      System.out.println("Done");
   }
}

输出

Subscribed
Processing 1
Processing 2
Processing 3
Processing 4
Processing 5
Processing 6
Processing 7
Processing 8
Processing 9
Processing 10
Processing done
Done