Reactive Stream API

Reactive stream is a specification created by engineers from netflix, lightbend and vmware. It contains 4 interfaces

• Reactive Streams is a specification that provides a standard for asynchronous stream processing with non-blocking back pressure.
• It defines a set of interfaces and contracts that enable interoperability between different reactive libraries and components.
• It defines a set of rules for asynchronous stream processing with non-blocking back pressure
• The Reactive Streams API allows developers to build reactive applications and stream processing pipelines in a consistent and composable manner.
• Reactive streams are introduced in java9

Reactive streams are immutable

1. Publisher
2. Subscriber
3. Subscription
4. Processor

Publisher

• A Publisher is a provider of a potentially unbounded number of sequenced elements, publishing them according to the demand received from its Subscriber(s)
• Publisher represents the datasource eg: database, remoteservers etc. which holds the data.
• A Publisher can serve multiple Subscribers subscribed subscribe(Subscriber)

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public interface publisher<T>{
  public void subscribe(Subscriber s);
}

subscribe

• Request Publisher to start streaming data.
• This is a "factory method" and can be called multiple times, each time starting a new Subscription.
• Each Subscription will work for only a single Subscriber.
• A Subscriber should only subscribe once to a single Publisher.
• If the Publisher rejects the subscription attempt or otherwise fails it will signal the error via Subscriber.onError(Throwable).
• Parameters:s - the Subscriber that will consume signals from this Publisher

Subscriber

public interace subscriber<T>{
  public void onSubscribe(Subscriber s);
  public void onNext(T t);
  public void onError(Throwable t);
  public void onComplete();
}

Subscription

public interace Subscription<T>{
  public void request(long n);
  public void cancel();
}

Processor

processor extends Subscriber and publisher

public interface Processor<T, R> extends Subscriber<T>, Publisher<R>{
}