Class PublishProcessor<T>
- java.lang.Object
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- io.reactivex.rxjava3.core.Flowable<T>
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- io.reactivex.rxjava3.processors.FlowableProcessor<T>
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- io.reactivex.rxjava3.processors.PublishProcessor<T>
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- Type Parameters:
T
- the value type multicasted to Subscribers.
- All Implemented Interfaces:
FlowableSubscriber<T>
,org.reactivestreams.Processor<T,T>
,org.reactivestreams.Publisher<T>
,org.reactivestreams.Subscriber<T>
public final class PublishProcessor<@NonNull T> extends FlowableProcessor<T>
Processor that multicasts all subsequently observed items to its currentSubscriber
s.This processor does not have a public constructor by design; a new empty instance of this
PublishProcessor
can be created via thecreate()
method.Since a
PublishProcessor
is a Reactive StreamsProcessor
type,null
s are not allowed (Rule 2.13) as parameters toonNext(Object)
andonError(Throwable)
. Such calls will result in aNullPointerException
being thrown and the processor's state is not changed.PublishProcessor
is aFlowable
as well as aFlowableProcessor
, however, it does not coordinate backpressure between different subscribers and between an upstream source and a subscriber. If an upstream item is received viaonNext(Object)
, if a subscriber is not ready to receive an item, that subscriber is terminated via aMissingBackpressureException
. To avoid this case, useoffer(Object)
and retry sometime later if it returned false. ThePublishProcessor
'sSubscriber
-side consumes items in an unbounded manner.For a multicasting processor type that also coordinates between the downstream
Subscriber
s and the upstream source as well, consider usingMulticastProcessor
.When this
PublishProcessor
is terminated viaonError(Throwable)
oronComplete()
, lateSubscriber
s only receive the respective terminal event.Unlike a
BehaviorProcessor
, aPublishProcessor
doesn't retain/cache items, therefore, a newSubscriber
won't receive any past items.Even though
PublishProcessor
implements theSubscriber
interface, callingonSubscribe
is not required (Rule 2.12) if the processor is used as a standalone source. However, callingonSubscribe
after thePublishProcessor
reached its terminal state will result in the givenSubscription
being canceled immediately.Calling
onNext(Object)
,offer(Object)
,onError(Throwable)
andonComplete()
is required to be serialized (called from the same thread or called non-overlappingly from different threads through external means of serialization). TheFlowableProcessor.toSerialized()
method available to allFlowableProcessor
s provides such serialization and also protects against reentrance (i.e., when a downstreamSubscriber
consuming this processor also wants to callonNext(Object)
on this processor recursively). Note that serializing overoffer(Object)
is not supported throughtoSerialized()
because it is a method available on thePublishProcessor
andBehaviorProcessor
classes only.This
PublishProcessor
supports the standard state-peeking methodshasComplete()
,hasThrowable()
,getThrowable()
andhasSubscribers()
.- Backpressure:
- The processor does not coordinate backpressure for its subscribers and implements a weaker
onSubscribe
which calls requestsLong.MAX_VALUE
from the incoming Subscriptions. This makes it possible to subscribe thePublishProcessor
to multiple sources (note on serialization though) unlike the standardSubscriber
contract. Child subscribers, however, are not overflown but receive anIllegalStateException
in case their requested amount is zero. - Scheduler:
PublishProcessor
does not operate by default on a particularScheduler
and theSubscriber
s get notified on the thread the respectiveonXXX
methods were invoked.- Error handling:
- When the
onError(Throwable)
is called, thePublishProcessor
enters into a terminal state and emits the sameThrowable
instance to the last set ofSubscriber
s. During this emission, if one or moreSubscriber
s cancel their respectiveSubscription
s, theThrowable
is delivered to the global error handler viaRxJavaPlugins.onError(Throwable)
(multiple times if multipleSubscriber
s cancel at once). If there were noSubscriber
s subscribed to thisPublishProcessor
when theonError()
was called, the global error handler is not invoked.
PublishProcessor<Object> processor = PublishProcessor.create(); // subscriber1 will receive all onNext and onComplete events processor.subscribe(subscriber1); processor.onNext("one"); processor.onNext("two"); // subscriber2 will only receive "three" and onComplete processor.subscribe(subscriber2); processor.onNext("three"); processor.onComplete();
- See Also:
MulticastProcessor
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Nested Class Summary
Nested Classes Modifier and Type Class Description (package private) static class
PublishProcessor.PublishSubscription<T>
Wraps the actual subscriber, tracks its requests and makes cancellation to remove itself from the current subscribers array.
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Field Summary
Fields Modifier and Type Field Description (package private) static PublishProcessor.PublishSubscription[]
EMPTY
An empty subscribers array to avoid allocating it all the time.(package private) java.lang.Throwable
error
The error, write before terminating and read after checking subscribers.(package private) java.util.concurrent.atomic.AtomicReference<PublishProcessor.PublishSubscription<T>[]>
subscribers
The array of currently subscribed subscribers.(package private) static PublishProcessor.PublishSubscription[]
TERMINATED
The terminated indicator for the subscribers array.
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Constructor Summary
Constructors Constructor Description PublishProcessor()
Constructs a PublishProcessor.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description (package private) boolean
add(PublishProcessor.PublishSubscription<@NonNull T> ps)
Tries to add the given subscriber to the subscribers array atomically or returns false if this processor has terminated.static <T> @NonNull PublishProcessor<T>
create()
Constructs a PublishProcessor.@Nullable java.lang.Throwable
getThrowable()
Returns the error that caused the FlowableProcessor to terminate or null if the FlowableProcessor hasn't terminated yet.boolean
hasComplete()
Returns true if the FlowableProcessor has reached a terminal state through a complete event.boolean
hasSubscribers()
Returns true if the FlowableProcessor has subscribers.boolean
hasThrowable()
Returns true if the FlowableProcessor has reached a terminal state through an error event.boolean
offer(@NonNull T t)
Tries to emit the item to all currently subscribedSubscriber
s if all of them has requested some value, returnsfalse
otherwise.void
onComplete()
void
onError(@NonNull java.lang.Throwable t)
void
onNext(@NonNull T t)
void
onSubscribe(@NonNull org.reactivestreams.Subscription s)
Implementors of this method should make sure everything that needs to be visible inSubscriber.onNext(Object)
is established before callingSubscription.request(long)
.(package private) void
remove(PublishProcessor.PublishSubscription<@NonNull T> ps)
Atomically removes the given subscriber if it is subscribed to this processor.protected void
subscribeActual(@NonNull org.reactivestreams.Subscriber<? super @NonNull T> t)
Operator implementations (both source and intermediate) should implement this method that performs the necessary business logic and handles the incomingSubscriber
s.-
Methods inherited from class io.reactivex.rxjava3.processors.FlowableProcessor
toSerialized
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Methods inherited from class io.reactivex.rxjava3.core.Flowable
all, amb, ambArray, ambWith, any, blockingFirst, blockingFirst, blockingForEach, blockingForEach, blockingIterable, blockingIterable, blockingLast, blockingLast, blockingLatest, blockingMostRecent, blockingNext, blockingSingle, blockingSingle, blockingStream, blockingStream, blockingSubscribe, blockingSubscribe, blockingSubscribe, blockingSubscribe, blockingSubscribe, blockingSubscribe, blockingSubscribe, blockingSubscribe, buffer, buffer, buffer, buffer, buffer, buffer, buffer, buffer, buffer, buffer, buffer, buffer, buffer, buffer, buffer, buffer, buffer, bufferSize, cache, cacheWithInitialCapacity, cast, collect, collect, collectInto, combineLatest, combineLatest, combineLatest, combineLatest, combineLatest, combineLatest, combineLatest, combineLatest, combineLatest, combineLatest, combineLatestArray, combineLatestArray, combineLatestArrayDelayError, combineLatestArrayDelayError, combineLatestDelayError, combineLatestDelayError, compose, concat, concat, concat, concat, concat, concat, concatArray, concatArrayDelayError, concatArrayEager, concatArrayEager, concatArrayEagerDelayError, concatArrayEagerDelayError, concatDelayError, concatDelayError, concatDelayError, concatEager, concatEager, concatEager, concatEager, concatEagerDelayError, concatEagerDelayError, concatEagerDelayError, concatEagerDelayError, concatMap, concatMap, concatMap, concatMapCompletable, concatMapCompletable, concatMapCompletableDelayError, concatMapCompletableDelayError, concatMapCompletableDelayError, concatMapDelayError, concatMapDelayError, concatMapDelayError, concatMapEager, concatMapEager, concatMapEagerDelayError, concatMapEagerDelayError, concatMapIterable, concatMapIterable, concatMapMaybe, concatMapMaybe, concatMapMaybeDelayError, concatMapMaybeDelayError, concatMapMaybeDelayError, concatMapSingle, concatMapSingle, concatMapSingleDelayError, concatMapSingleDelayError, concatMapSingleDelayError, concatMapStream, concatMapStream, concatWith, concatWith, concatWith, concatWith, contains, count, create, debounce, debounce, debounce, debounce, defaultIfEmpty, defer, delay, delay, delay, delay, delay, delay, delaySubscription, delaySubscription, delaySubscription, dematerialize, distinct, distinct, distinct, distinctUntilChanged, distinctUntilChanged, distinctUntilChanged, doAfterNext, doAfterTerminate, doFinally, doOnCancel, doOnComplete, doOnEach, doOnEach, doOnError, doOnLifecycle, doOnNext, doOnRequest, doOnSubscribe, doOnTerminate, elementAt, elementAt, elementAtOrError, empty, error, error, filter, first, firstElement, firstOrError, firstOrErrorStage, firstStage, flatMap, flatMap, flatMap, flatMap, flatMap, flatMap, flatMap, flatMap, flatMap, flatMap, flatMap, flatMap, flatMapCompletable, flatMapCompletable, flatMapIterable, flatMapIterable, flatMapIterable, flatMapIterable, flatMapMaybe, flatMapMaybe, flatMapSingle, flatMapSingle, flatMapStream, flatMapStream, forEach, forEachWhile, forEachWhile, forEachWhile, fromAction, fromArray, fromCallable, fromCompletable, fromCompletionStage, fromFuture, fromFuture, fromIterable, fromMaybe, fromObservable, fromOptional, fromPublisher, fromRunnable, fromSingle, fromStream, fromSupplier, generate, generate, generate, generate, generate, groupBy, groupBy, groupBy, groupBy, groupBy, groupBy, groupJoin, hide, ignoreElements, interval, interval, interval, interval, intervalRange, intervalRange, isEmpty, join, just, just, just, just, just, just, just, just, just, just, last, lastElement, lastOrError, lastOrErrorStage, lastStage, lift, map, mapOptional, materialize, merge, merge, merge, merge, merge, merge, merge, merge, mergeArray, mergeArray, mergeArrayDelayError, mergeArrayDelayError, mergeDelayError, mergeDelayError, mergeDelayError, mergeDelayError, mergeDelayError, mergeDelayError, mergeDelayError, mergeDelayError, mergeWith, mergeWith, mergeWith, mergeWith, never, observeOn, observeOn, observeOn, ofType, onBackpressureBuffer, onBackpressureBuffer, onBackpressureBuffer, onBackpressureBuffer, onBackpressureBuffer, onBackpressureBuffer, onBackpressureBuffer, onBackpressureBuffer, onBackpressureBuffer, onBackpressureBuffer, onBackpressureDrop, onBackpressureDrop, onBackpressureLatest, onBackpressureLatest, onBackpressureReduce, onBackpressureReduce, onErrorComplete, onErrorComplete, onErrorResumeNext, onErrorResumeWith, onErrorReturn, onErrorReturnItem, onTerminateDetach, parallel, parallel, parallel, publish, publish, publish, publish, range, rangeLong, rebatchRequests, reduce, reduce, reduceWith, repeat, repeat, repeatUntil, repeatWhen, replay, replay, replay, replay, replay, replay, replay, replay, replay, replay, replay, replay, replay, replay, replay, replay, replay, replay, retry, retry, retry, retry, retry, retryUntil, retryWhen, safeSubscribe, sample, sample, sample, sample, sample, sample, sample, scan, scan, scanWith, sequenceEqual, sequenceEqual, sequenceEqual, sequenceEqual, serialize, share, single, singleElement, singleOrError, singleOrErrorStage, singleStage, skip, skip, skip, skipLast, skipLast, skipLast, skipLast, skipLast, skipLast, skipUntil, skipWhile, sorted, sorted, startWith, startWith, startWith, startWith, startWithArray, startWithItem, startWithIterable, subscribe, subscribe, subscribe, subscribe, subscribe, subscribe, subscribe, subscribeOn, subscribeOn, subscribeWith, switchIfEmpty, switchMap, switchMap, switchMapCompletable, switchMapCompletableDelayError, switchMapDelayError, switchMapDelayError, switchMapMaybe, switchMapMaybeDelayError, switchMapSingle, switchMapSingleDelayError, switchOnNext, switchOnNext, switchOnNextDelayError, switchOnNextDelayError, take, take, take, takeLast, takeLast, takeLast, takeLast, takeLast, takeLast, takeLast, takeLast, takeLast, takeUntil, takeUntil, takeWhile, test, test, test, throttleFirst, throttleFirst, throttleFirst, throttleLast, throttleLast, throttleLast, throttleLatest, throttleLatest, throttleLatest, throttleLatest, throttleLatest, 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Field Detail
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TERMINATED
static final PublishProcessor.PublishSubscription[] TERMINATED
The terminated indicator for the subscribers array.
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EMPTY
static final PublishProcessor.PublishSubscription[] EMPTY
An empty subscribers array to avoid allocating it all the time.
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subscribers
final java.util.concurrent.atomic.AtomicReference<PublishProcessor.PublishSubscription<T>[]> subscribers
The array of currently subscribed subscribers.
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error
java.lang.Throwable error
The error, write before terminating and read after checking subscribers.
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Method Detail
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create
@CheckReturnValue @NonNull public static <T> @NonNull PublishProcessor<T> create()
Constructs a PublishProcessor.- Type Parameters:
T
- the value type- Returns:
- the new PublishProcessor
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subscribeActual
protected void subscribeActual(@NonNull @NonNull org.reactivestreams.Subscriber<? super @NonNull T> t)
Description copied from class:Flowable
Operator implementations (both source and intermediate) should implement this method that performs the necessary business logic and handles the incomingSubscriber
s.There is no need to call any of the plugin hooks on the current
Flowable
instance or theSubscriber
; all hooks and basic safeguards have been applied byFlowable.subscribe(Subscriber)
before this method gets called.- Specified by:
subscribeActual
in classFlowable<T>
- Parameters:
t
- the incomingSubscriber
, nevernull
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add
boolean add(PublishProcessor.PublishSubscription<@NonNull T> ps)
Tries to add the given subscriber to the subscribers array atomically or returns false if this processor has terminated.- Parameters:
ps
- the subscriber to add- Returns:
- true if successful, false if this processor has terminated
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remove
void remove(PublishProcessor.PublishSubscription<@NonNull T> ps)
Atomically removes the given subscriber if it is subscribed to this processor.- Parameters:
ps
- the subscription wrapping a subscriber to remove
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onSubscribe
public void onSubscribe(@NonNull @NonNull org.reactivestreams.Subscription s)
Description copied from interface:FlowableSubscriber
Implementors of this method should make sure everything that needs to be visible inSubscriber.onNext(Object)
is established before callingSubscription.request(long)
. In practice this means no initialization should happen after therequest()
call and additional behavior is thread safe in respect toonNext
.
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onComplete
public void onComplete()
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offer
@CheckReturnValue public boolean offer(@NonNull @NonNull T t)
Tries to emit the item to all currently subscribedSubscriber
s if all of them has requested some value, returnsfalse
otherwise.This method should be called in a sequential manner just like the
onXXX
methods of thisPublishProcessor
.History: 2.0.8 - experimental
- Parameters:
t
- the item to emit, notnull
- Returns:
true
if the item was emitted to allSubscriber
s- Throws:
java.lang.NullPointerException
- ift
isnull
- Since:
- 2.2
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hasSubscribers
@CheckReturnValue public boolean hasSubscribers()
Description copied from class:FlowableProcessor
Returns true if the FlowableProcessor has subscribers.The method is thread-safe.
- Specified by:
hasSubscribers
in classFlowableProcessor<T>
- Returns:
- true if the FlowableProcessor has subscribers
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getThrowable
@Nullable @CheckReturnValue public @Nullable java.lang.Throwable getThrowable()
Description copied from class:FlowableProcessor
Returns the error that caused the FlowableProcessor to terminate or null if the FlowableProcessor hasn't terminated yet.The method is thread-safe.
- Specified by:
getThrowable
in classFlowableProcessor<T>
- Returns:
- the error that caused the FlowableProcessor to terminate or null if the FlowableProcessor hasn't terminated yet
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hasThrowable
@CheckReturnValue public boolean hasThrowable()
Description copied from class:FlowableProcessor
Returns true if the FlowableProcessor has reached a terminal state through an error event.The method is thread-safe.
- Specified by:
hasThrowable
in classFlowableProcessor<T>
- Returns:
- true if the FlowableProcessor has reached a terminal state through an error event
- See Also:
FlowableProcessor.getThrowable()
,FlowableProcessor.hasComplete()
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hasComplete
@CheckReturnValue public boolean hasComplete()
Description copied from class:FlowableProcessor
Returns true if the FlowableProcessor has reached a terminal state through a complete event.The method is thread-safe.
- Specified by:
hasComplete
in classFlowableProcessor<T>
- Returns:
- true if the FlowableProcessor has reached a terminal state through a complete event
- See Also:
FlowableProcessor.hasThrowable()
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