Publisher
Subscriber
Subscription
Processor
-----------------------------------
public interface Publisher<T> {
/**
* Request {@link Publisher} to start streaming data.
* <p>
* This is a "factory method" and can be called multiple times, each time starting a new {@link Subscription}.
* <p>
* Each {@link Subscription} will work for only a single {@link Subscriber}.
* <p>
* A {@link Subscriber} should only subscribe once to a single {@link Publisher}.
* <p>
* If the {@link Publisher} rejects the subscription attempt or otherwise fails it will
* signal the error via {@link Subscriber#onError}.
*
* @param s the {@link Subscriber} that will consume signals from this {@link Publisher}
*/
public void subscribe(Subscriber<? super T> s);
}public interface Subscriber<T> {
/**
* Invoked after calling {@link Publisher#subscribe(Subscriber)}.
* <p>
* No data will start flowing until {@link Subscription#request(long)} is invoked.
* <p>
* It is the responsibility of this {@link Subscriber} instance to call {@link Subscription#request(long)} whenever more data is wanted.
* <p>
* The {@link Publisher} will send notifications only in response to {@link Subscription#request(long)}.
*
* @param s
* {@link Subscription} that allows requesting data via {@link Subscription#request(long)}
*/
public void onSubscribe(Subscription s);
/**
* Data notification sent by the {@link Publisher} in response to requests to {@link Subscription#request(long)}.
*
* @param t the element signaled
*/
public void onNext(T t);
/**
* Failed terminal state.
* <p>
* No further events will be sent even if {@link Subscription#request(long)} is invoked again.
*
* @param t the throwable signaled
*/
public void onError(Throwable t);
/**
* Successful terminal state.
* <p>
* No further events will be sent even if {@link Subscription#request(long)} is invoked again.
*/
public void onComplete();
}public interface Subscription {
/**
* No events will be sent by a {@link Publisher} until demand is signaled via this method.
* <p>
* It can be called however often and whenever needed—but the outstanding cumulative demand must never exceed Long.MAX_VALUE.
* An outstanding cumulative demand of Long.MAX_VALUE may be treated by the {@link Publisher} as "effectively unbounded".
* <p>
* Whatever has been requested can be sent by the {@link Publisher} so only signal demand for what can be safely handled.
* <p>
* A {@link Publisher} can send less than is requested if the stream ends but
* then must emit either {@link Subscriber#onError(Throwable)} or {@link Subscriber#onComplete()}.
*
* @param n the strictly positive number of elements to requests to the upstream {@link Publisher}
*/
public void request(long n);
/**
* Request the {@link Publisher} to stop sending data and clean up resources.
* <p>
* Data may still be sent to meet previously signalled demand after calling cancel as this request is asynchronous.
*/
public void cancel();
}public interface Processor<T, R> extends Subscriber<T>, Publisher<R> {
}