Package com.linecorp.armeria.common.stream

Interface StreamMessage<T>

Type Parameters:

T - the type of element signaled

All Superinterfaces:

org.reactivestreams.Publisher<T>

All Known Subinterfaces:

HttpRequest, HttpRequestWriter, HttpResponse, HttpResponseWriter, PooledHttpRequest, PooledHttpResponse, PooledStreamMessage<T>

All Known Implementing Classes:

DefaultStreamMessage, DeferredStreamMessage, EmptyFixedStreamMessage, FilteredHttpRequest, FilteredHttpResponse, FilteredStreamMessage, OneElementFixedStreamMessage, PublisherBasedStreamMessage, RegularFixedStreamMessage, StreamMessageWrapper, TwoElementFixedStreamMessage

public interface StreamMessage<T>
extends org.reactivestreams.Publisher<T>

A variant of Reactive Streams Publisher, which allows only one Subscriber. Unlike a usual Publisher, a StreamMessage can stream itself only once. It has the following additional operations on top of what the Reactive Streams API provides:

• isOpen()
• isEmpty()
• whenComplete()
• abort()

When is a StreamMessage fully consumed?

A StreamMessage is complete (or 'fully consumed') when:

• the Subscriber consumes all elements and Subscriber.onComplete() is invoked,
• an error occurred and Subscriber.onError(Throwable) is invoked,
• the Subscription has been cancelled or
• abort() has been requested.

When fully consumed, the CompletableFuture returned by whenComplete() will complete, which you may find useful because Subscriber does not notify you when a stream is cancelled.

Publication and Consumption of ReferenceCounted objects

StreamMessage will reject the publication request of a ReferenceCounted object except ByteBuf and ByteBufHolder.

StreamMessage will discard the publication request of a ByteBuf or a ByteBufHolder silently and release it automatically when the publication is attempted after the stream is closed.

For ByteBuf and ByteBufHolder, StreamMessage will convert them into their respective unpooled versions that never leak, so that the Subscriber does not need to worry about leaks.

Subscriber.onError(Throwable) is invoked when any exception is raised except the CancelledSubscriptionException which is caused by Subscription.cancel(). If you want your Subscriber get notified by Subscriber.onError(Throwable) when Subscription.cancel() is called, specify SubscriptionOption.NOTIFY_CANCELLATION when you subscribe.

Method Summary

Modifier and Type	Method	Description
void	abort()	Closes this stream with AbortedStreamException and prevents further subscription.
void	abort(Throwable cause)	Closes this stream with the specified Throwable and prevents further subscription.
default EventExecutor	defaultSubscriberExecutor()	Returns the default EventExecutor which will be used when a user subscribes using subscribe(Subscriber), subscribe(Subscriber, SubscriptionOption...).
default boolean	isComplete()	Returns true if this stream is complete, either successfully or exceptionally, including cancellation and abortion.
boolean	isEmpty()	Returns true if this stream has been closed and did not publish any elements.
boolean	isOpen()	Returns true if this stream is not closed yet.
static <T> StreamMessage<T>	of()	Creates a new StreamMessage that will publish no objects, just a close event.
static <T> StreamMessage<T>	of(T obj)	Creates a new StreamMessage that will publish the single obj.
static <T> StreamMessage<T>	of(T... objs)	Creates a new StreamMessage that will publish the given objs.
static <T> StreamMessage<T>	of(T obj1, T obj2)	Creates a new StreamMessage that will publish the two obj1 and obj2.
default void	subscribe(org.reactivestreams.Subscriber<? super T> subscriber)	Requests to start streaming data to the specified Subscriber.
default void	subscribe(org.reactivestreams.Subscriber<? super T> subscriber, SubscriptionOption... options)	Requests to start streaming data to the specified Subscriber.
void	subscribe(org.reactivestreams.Subscriber<? super T> subscriber, EventExecutor executor)	Requests to start streaming data to the specified Subscriber.
void	subscribe(org.reactivestreams.Subscriber<? super T> subscriber, EventExecutor executor, SubscriptionOption... options)	Requests to start streaming data to the specified Subscriber.
default StreamMessageDuplicator<T>	toDuplicator()	Returns a new StreamMessageDuplicator that duplicates this StreamMessage into one or more StreamMessages, which publish the same elements.
default StreamMessageDuplicator<T>	toDuplicator(EventExecutor executor)	Returns a new StreamMessageDuplicator that duplicates this StreamMessage into one or more StreamMessages, which publish the same elements.
CompletableFuture<Void>	whenComplete()	Returns a CompletableFuture that completes when this stream is complete, either successfully or exceptionally, including cancellation and abortion.

Method Details

of

static <T> StreamMessage<T> of()

Creates a new StreamMessage that will publish no objects, just a close event.

of

static <T> StreamMessage<T> of(T obj)

Creates a new StreamMessage that will publish the single obj.

of

static <T> StreamMessage<T> of(T obj1, T obj2)

Creates a new StreamMessage that will publish the two obj1 and obj2.

of

@SafeVarargs static <T> StreamMessage<T> of(T... objs)

Creates a new StreamMessage that will publish the given objs.

isOpen

boolean isOpen()

Returns true if this stream is not closed yet. Note that a stream may not be complete even if it's closed; a stream is complete when it's fully consumed by a Subscriber.

isEmpty

boolean isEmpty()

Returns true if this stream has been closed and did not publish any elements. Note that this method will not return true when the stream is open even if it has not published anything so far, because it may publish something later.

isComplete

default boolean isComplete()

Returns true if this stream is complete, either successfully or exceptionally, including cancellation and abortion.

A StreamMessage is complete (or 'fully consumed') when:

• the Subscriber consumes all elements and Subscriber.onComplete() is invoked,
• an error occurred and Subscriber.onError(Throwable) is invoked,
• the Subscription has been cancelled or
• abort() has been requested.

whenComplete

CompletableFuture<Void> whenComplete()

Returns a CompletableFuture that completes when this stream is complete, either successfully or exceptionally, including cancellation and abortion.

A StreamMessage is complete (or 'fully consumed') when:

• the Subscriber consumes all elements and Subscriber.onComplete() is invoked,
• an error occurred and Subscriber.onError(Throwable) is invoked,
• the Subscription has been cancelled or
• abort() has been requested.

subscribe

default void subscribe(org.reactivestreams.Subscriber<? super T> subscriber)

Requests to start streaming data to the specified Subscriber. If there is a problem subscribing, Subscriber.onError(Throwable) will be invoked with one of the following exceptions:

• IllegalStateException if other Subscriber subscribed to this stream already.
• AbortedStreamException if this stream has been aborted.
• CancelledSubscriptionException if this stream has been cancelled and SubscriptionOption.NOTIFY_CANCELLATION is specified when subscribed.
• Other exceptions that occurred due to an error while retrieving the elements.

Specified by:

subscribe in interface org.reactivestreams.Publisher<T>

subscribe

default void subscribe(org.reactivestreams.Subscriber<? super T> subscriber, SubscriptionOption... options)

Requests to start streaming data to the specified Subscriber. If there is a problem subscribing, Subscriber.onError(Throwable) will be invoked with one of the following exceptions:

• IllegalStateException if other Subscriber subscribed to this stream already.
• AbortedStreamException if this stream has been aborted.
• CancelledSubscriptionException if this stream has been cancelled and SubscriptionOption.NOTIFY_CANCELLATION is specified when subscribed.
• Other exceptions that occurred due to an error while retrieving the elements.

Parameters:

options - SubscriptionOptions to subscribe with

subscribe

void subscribe(org.reactivestreams.Subscriber<? super T> subscriber, EventExecutor executor)

Requests to start streaming data to the specified Subscriber. If there is a problem subscribing, Subscriber.onError(Throwable) will be invoked with one of the following exceptions:

• IllegalStateException if other Subscriber subscribed to this stream already.
• AbortedStreamException if this stream has been aborted.
• CancelledSubscriptionException if this stream has been cancelled and SubscriptionOption.NOTIFY_CANCELLATION is specified when subscribed.
• Other exceptions that occurred due to an error while retrieving the elements.

Parameters:

executor - the executor to subscribe

subscribe

void subscribe(org.reactivestreams.Subscriber<? super T> subscriber, EventExecutor executor, SubscriptionOption... options)

Requests to start streaming data to the specified Subscriber. If there is a problem subscribing, Subscriber.onError(Throwable) will be invoked with one of the following exceptions:

• IllegalStateException if other Subscriber subscribed to this stream already.
• AbortedStreamException if this stream has been aborted.
• CancelledSubscriptionException if this stream has been cancelled and SubscriptionOption.NOTIFY_CANCELLATION is specified when subscribed.
• Other exceptions that occurred due to an error while retrieving the elements.

Parameters:

executor - the executor to subscribe

options - SubscriptionOptions to subscribe with

toDuplicator

default StreamMessageDuplicator<T> toDuplicator()

Returns a new StreamMessageDuplicator that duplicates this StreamMessage into one or more StreamMessages, which publish the same elements. Note that you cannot subscribe to this StreamMessage anymore after you call this method. To subscribe, call StreamMessageDuplicator.duplicate() from the returned StreamMessageDuplicator.

toDuplicator

default StreamMessageDuplicator<T> toDuplicator(EventExecutor executor)

Returns a new StreamMessageDuplicator that duplicates this StreamMessage into one or more StreamMessages, which publish the same elements. Note that you cannot subscribe to this StreamMessage anymore after you call this method. To subscribe, call StreamMessageDuplicator.duplicate() from the returned StreamMessageDuplicator.

Parameters:

executor - the executor to duplicate

defaultSubscriberExecutor

default EventExecutor defaultSubscriberExecutor()

Returns the default EventExecutor which will be used when a user subscribes using subscribe(Subscriber), subscribe(Subscriber, SubscriptionOption...).

Please note that if this method is called multiple times, the returned EventExecutors can be different depending on this StreamMessage implementation.

abort

void abort()

Closes this stream with AbortedStreamException and prevents further subscription. A Subscriber that attempts to subscribe to an aborted stream will be notified with an AbortedStreamException via Subscriber.onError(Throwable). Calling this method on a closed or aborted stream has no effect.

abort

void abort(Throwable cause)

Closes this stream with the specified Throwable and prevents further subscription. A Subscriber that attempts to subscribe to an aborted stream will be notified with the specified Throwable via Subscriber.onError(Throwable). Calling this method on a closed or aborted stream has no effect.