org.eclipse.microprofile.reactive.streams.operators

Class ReactiveStreams

java.lang.Object

org.eclipse.microprofile.reactive.streams.operators.ReactiveStreams

public class ReactiveStreams
extends Object

Primary entry point into the Reactive Streams utility API.

This class provides factory methods for publisher and processor builders, which can then be subsequently manipulated using their respective APIs.

The documentation for each operator uses marble diagrams to visualize how the operator functions. Each element flowing in and out of the stream is represented as a coloured marble that has a value, with the operator applying some transformation or some side effect, termination and error signals potentially being passed, and for operators that subscribe to the stream, an output value being redeemed at the end.

Below is an example diagram labelling all the parts of the stream.

Method Summary

Modifier and Type	Method and Description
static <T> ProcessorBuilder<T,T>	builder() Create a ProcessorBuilder.
static <T> PublisherBuilder<T>	concat(PublisherBuilder<? extends T> a, PublisherBuilder<? extends T> b) Concatenates two publishers.
static <T,R> ProcessorBuilder<T,R>	coupled(org.reactivestreams.Subscriber<? super T> subscriber, org.reactivestreams.Publisher<? extends R> publisher) Creates a ProcessorBuilder by coupling a Subscriber to a Publisher.
static <T,R> ProcessorBuilder<T,R>	coupled(SubscriberBuilder<? super T,?> subscriber, PublisherBuilder<? extends R> publisher) Creates a ProcessorBuilder by coupling a SubscriberBuilder to a PublisherBuilder.
static <T> PublisherBuilder<T>	empty() Create an empty PublisherBuilder.
static <T> PublisherBuilder<T>	failed(Throwable t) Create a failed PublisherBuilder.
static <T> PublisherBuilder<T>	fromCompletionStage(CompletionStage<? extends T> completionStage) Creates a publisher from a CompletionStage.
static <T> PublisherBuilder<T>	fromCompletionStageNullable(CompletionStage<? extends T> completionStage) Creates a publisher from a CompletionStage.
static <T> PublisherBuilder<T>	fromIterable(Iterable<? extends T> ts) Create a PublisherBuilder that will emits the elements produced by the passed in Iterable.
static <T,R> ProcessorBuilder<T,R>	fromProcessor(org.reactivestreams.Processor<? super T,? extends R> processor) Create a ProcessorBuilder from the given Processor.
static <T> PublisherBuilder<T>	fromPublisher(org.reactivestreams.Publisher<? extends T> publisher) Create a PublisherBuilder from the given Publisher.
static <T> SubscriberBuilder<T,Void>	fromSubscriber(org.reactivestreams.Subscriber<? extends T> subscriber) Create a SubscriberBuilder from the given Subscriber.
static <T> PublisherBuilder<T>	generate(Supplier<? extends T> s) Creates an infinite stream that emits elements supplied by the supplier s.
static <T> PublisherBuilder<T>	iterate(T seed, UnaryOperator<T> f) Creates an infinite stream produced by the iterative application of the function f to an initial element seed consisting of seed, f(seed), f(f(seed)), etc.
static <T> PublisherBuilder<T>	of(T... ts) Create a PublisherBuilder that emits the given elements.
static <T> PublisherBuilder<T>	of(T t) Create a PublisherBuilder that emits a single element.
static <T> PublisherBuilder<T>	ofNullable(T t) Create a PublisherBuilder that will emit a single element if t is not null, otherwise will be empty.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

fromPublisher

public static <T> PublisherBuilder<T> fromPublisher(org.reactivestreams.Publisher<? extends T> publisher)

Create a PublisherBuilder from the given Publisher.

Type Parameters:

T - The type of the elements that the publisher produces.

Parameters:

publisher - The publisher to wrap.

Returns:

A publisher builder that wraps the given publisher.

of

public static <T> PublisherBuilder<T> of(T t)

Create a PublisherBuilder that emits a single element.

Type Parameters:

T - The type of the element.

Parameters:

t - The element to emit.

Returns:

A publisher builder that will emit the element.

of

public static <T> PublisherBuilder<T> of(T... ts)

Create a PublisherBuilder that emits the given elements.

Type Parameters:

T - The type of the elements.

Parameters:

ts - The elements to emit.

Returns:

A publisher builder that will emit the elements.

empty

public static <T> PublisherBuilder<T> empty()

Create an empty PublisherBuilder.

Type Parameters:

T - The type of the publisher builder.

Returns:

A publisher builder that will just emit a completion signal.

ofNullable

public static <T> PublisherBuilder<T> ofNullable(T t)

Create a PublisherBuilder that will emit a single element if t is not null, otherwise will be empty.

Type Parameters:

T - The type of the element.

Parameters:

t - The element to emit, null if to element should be emitted.

Returns:

A publisher builder that optionally emits a single element.

fromIterable

public static <T> PublisherBuilder<T> fromIterable(Iterable<? extends T> ts)

Create a PublisherBuilder that will emits the elements produced by the passed in Iterable.

Type Parameters:

T - The type of the elements.

Parameters:

ts - The elements to emit.

Returns:

A publisher builder that emits the elements of the iterable.

failed

public static <T> PublisherBuilder<T> failed(Throwable t)

Create a failed PublisherBuilder.

This publisher will just emit an error.

Type Parameters:

T - The type of the publisher builder.

Parameters:

t - The error te emit.

Returns:

A publisher builder that completes the stream with an error.

builder

public static <T> ProcessorBuilder<T,T> builder()

Create a ProcessorBuilder. This builder will start as an identity processor.

Type Parameters:

T - The type of elements that the processor consumes and emits.

Returns:

The identity processor builder.

fromProcessor

public static <T,R> ProcessorBuilder<T,R> fromProcessor(org.reactivestreams.Processor<? super T,? extends R> processor)

Create a ProcessorBuilder from the given Processor.

Type Parameters:

T - The type of the elements that the processor consumes.

R - The type of the elements that the processor emits.

Parameters:

processor - The processor to be wrapped.

Returns:

A processor builder that wraps the processor.

fromSubscriber

public static <T> SubscriberBuilder<T,Void> fromSubscriber(org.reactivestreams.Subscriber<? extends T> subscriber)

Create a SubscriberBuilder from the given Subscriber. The subscriber can only be used to create a single subscriber builder.

Type Parameters:

T - The type of elements that the subscriber consumes.

Parameters:

subscriber - The subscriber to be wrapped.

Returns:

A subscriber builder that wraps the subscriber.

iterate

public static <T> PublisherBuilder<T> iterate(T seed,
                                              UnaryOperator<T> f)

Creates an infinite stream produced by the iterative application of the function f to an initial element seed consisting of seed, f(seed), f(f(seed)), etc.

Type Parameters:

T - The type of stream elements.

Parameters:

seed - The initial element.

f - A function applied to the previous element to produce the next element.

Returns:

A publisher builder.

generate

public static <T> PublisherBuilder<T> generate(Supplier<? extends T> s)

Creates an infinite stream that emits elements supplied by the supplier s.

Type Parameters:

T - The type of stream elements.

Parameters:

s - The supplier.

Returns:

A publisher builder.

concat

public static <T> PublisherBuilder<T> concat(PublisherBuilder<? extends T> a,
                                             PublisherBuilder<? extends T> b)

Concatenates two publishers.

The resulting stream will be produced by subscribing to the first publisher, and emitting the elements it emits, until it emits a completion signal, at which point the second publisher will be subscribed to, and its elements will be emitted.

If the first publisher completes with an error signal, then the second publisher will be subscribed to but immediately cancelled, none of its elements will be emitted. This ensures that hot publishers are cleaned up. If downstream emits a cancellation signal before the first publisher finishes, it will be passed to both publishers.

Type Parameters:

T - The type of stream elements.

Parameters:

a - The first publisher.

b - The second publisher.

Returns:

A publisher builder.

fromCompletionStage

public static <T> PublisherBuilder<T> fromCompletionStage(CompletionStage<? extends T> completionStage)

Creates a publisher from a CompletionStage.

When the CompletionStage is redeemed, the publisher will emit the redeemed element, and then signal completion. If the completion stage is redeemed with null, the stream will be failed with a NullPointerException.

If the CompletionStage is completed with a failure, this failure will be propagated through the stream.

Type Parameters:

T - The type of the CompletionStage value.

Parameters:

completionStage - The CompletionStage to create the publisher from.

Returns:

A PublisherBuilder representation of this CompletionStage.

fromCompletionStageNullable

public static <T> PublisherBuilder<T> fromCompletionStageNullable(CompletionStage<? extends T> completionStage)

Creates a publisher from a CompletionStage.

When the CompletionStage is redeemed, the publisher will emit the redeemed element, and then signal completion. If the completion stage is redeemed with null, the stream will be immediately completed with no element, ie, it will be an empty stream.

If the CompletionStage is completed with a failure, this failure will be propagated through the stream.

Type Parameters:

T - The type of the CompletionStage value.

Parameters:

completionStage - The CompletionStage to create the publisher from.

Returns:

A PublisherBuilder representation of this CompletionStage.

coupled

public static <T,R> ProcessorBuilder<T,R> coupled(SubscriberBuilder<? super T,?> subscriber,
                                                  PublisherBuilder<? extends R> publisher)

Creates a ProcessorBuilder by coupling a SubscriberBuilder to a PublisherBuilder.

The resulting processor sends all the elements received to the passed in subscriber, and emits all the elements received from the passed in publisher.

In addition, the lifecycles of the subscriber and publisher are coupled, such that if one terminates or receives a termination signal, the other will be terminated. Below is a table of what signals are emited when.

Lifecycle signal propagation

Returned ProcessorBuilder inlet	Passed in SubscriberBuilder	Passed in PublisherBuilder	Returned ProcessorBuilder outlet
Cause: complete from upstream	Effect: complete	Effect: cancel	Effect: complete
Cause: error from upstream	Effect: error	Effect: cancel	Effect: error
Effect: cancel	Cause: cancels	Effect: cancel	Effect: complete
Effect: cancel	Effect: complete	Cause: completes	Effect: complete
Effect: cancel	Effect: error	Cause: errors	Effect: error
Effect: cancel	Effect: complete	Effect: cancel	Cause: cancel from downstream

Type Parameters:

T - The type of elements received.

R - The type of elements emitted.

Parameters:

subscriber - The subscriber builder to wrap.

publisher - The publisher builder to wrap.

Returns:

The coupled processor builder.

coupled

public static <T,R> ProcessorBuilder<T,R> coupled(org.reactivestreams.Subscriber<? super T> subscriber,
                                                  org.reactivestreams.Publisher<? extends R> publisher)

Creates a ProcessorBuilder by coupling a Subscriber to a Publisher.

The resulting processor sends all the elements received to the passed in subscriber, and emits all the elements received from the passed in publisher.

In addition, the lifecycles of the subscriber and publisher are coupled, such that if one terminates or receives a termination signal, the other will be terminated. Below is a table of what signals are emited when:

Lifecycle signal propagation

Returned ProcessorBuilder inlet	Passed in SubscriberBuilder	Passed in PublisherBuilder	Returned ProcessorBuilder outlet
Cause: complete from upstream	Effect: complete	Effect: cancel	Effect: complete
Cause: error from upstream	Effect: error	Effect: cancel	Effect: error
Effect: cancel	Cause: cancels	Effect: cancel	Effect: complete
Effect: cancel	Effect: complete	Cause: completes	Effect: complete
Effect: cancel	Effect: error	Cause: errors	Effect: error
Effect: cancel	Effect: complete	Effect: cancel	Cause: cancel from downstream

Type Parameters:

T - The type of elements received.

R - The type of elements emitted.

Parameters:

subscriber - The subscriber builder to wrap.

publisher - The publisher builder to wrap.

Returns:

The coupled processor builder.

See Also:

coupled(SubscriberBuilder, PublisherBuilder)