Class AsyncProcessor<T>
- Type Parameters:
T
- the value type
- All Implemented Interfaces:
FlowableSubscriber<T>
,org.reactivestreams.Processor<T,
,T> org.reactivestreams.Publisher<T>
,org.reactivestreams.Subscriber<T>
Subscriber
s.
This processor does not have a public constructor by design; a new empty instance of this
AsyncProcessor
can be created via the create()
method.
Since an AsyncProcessor
is a Reactive Streams Processor
type,
null
s are not allowed (Rule 2.13)
as parameters to onNext(Object)
and onError(Throwable)
. Such calls will result in a
NullPointerException
being thrown and the processor's state is not changed.
AsyncProcessor
is a Flowable
as well as a FlowableProcessor
and supports backpressure from the downstream but
its Subscriber
-side consumes items in an unbounded manner.
When this AsyncProcessor
is terminated via onError(Throwable)
, the
last observed item (if any) is cleared and late Subscriber
s only receive
the onError
event.
The AsyncProcessor
caches the latest item internally and it emits this item only when onComplete
is called.
Therefore, it is not recommended to use this Processor
with infinite or never-completing sources.
Even though AsyncProcessor
implements the Subscriber
interface, calling
onSubscribe
is not required (Rule 2.12)
if the processor is used as a standalone source. However, calling onSubscribe
after the AsyncProcessor
reached its terminal state will result in the
given Subscription
being canceled immediately.
Calling onNext(Object)
, onError(Throwable)
and onComplete()
is required to be serialized (called from the same thread or called non-overlappingly from different threads
through external means of serialization). The FlowableProcessor.toSerialized()
method available to all FlowableProcessor
s
provides such serialization and also protects against reentrance (i.e., when a downstream Subscriber
consuming this processor also wants to call onNext(Object)
on this processor recursively).
The implementation of onXXX
methods are technically thread-safe but non-serialized calls
to them may lead to undefined state in the currently subscribed Subscriber
s.
This AsyncProcessor
supports the standard state-peeking methods hasComplete()
, hasThrowable()
,
getThrowable()
and hasSubscribers()
as well as means to read the very last observed value -
after this AsyncProcessor
has been completed - in a non-blocking and thread-safe
manner via hasValue()
or getValue()
.
- Backpressure:
- The
AsyncProcessor
honors the backpressure of the downstreamSubscriber
s and won't emit its single value to a particularSubscriber
until thatSubscriber
has requested an item. When theAsyncProcessor
is subscribed to aFlowable
, the processor consumes thisFlowable
in an unbounded manner (requestingLong.MAX_VALUE
) as only the very last upstream item is retained by it. - Scheduler:
AsyncProcessor
does not operate by default on a particularScheduler
and theSubscriber
s get notified on the thread where the terminatingonError
oronComplete
methods were invoked.- Error handling:
- When the
onError(Throwable)
is called, theAsyncProcessor
enters into a terminal state and emits the sameThrowable
instance to the last set ofSubscriber
s. During this emission, if one or moreSubscriber
s dispose 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 thisAsyncProcessor
when theonError()
was called, the global error handler is not invoked.
Example usage:
AsyncProcessor<Object> processor = AsyncProcessor.create();
TestSubscriber<Object> ts1 = processor.test();
ts1.assertEmpty();
processor.onNext(1);
// AsyncProcessor only emits when onComplete was called.
ts1.assertEmpty();
processor.onNext(2);
processor.onComplete();
// onComplete triggers the emission of the last cached item and the onComplete event.
ts1.assertResult(2);
TestSubscriber<Object> ts2 = processor.test();
// late Subscribers receive the last cached item too
ts2.assertResult(2);
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Nested Class Summary
Nested ClassesModifier and TypeClassDescription(package private) static final class
-
Field Summary
FieldsModifier and TypeFieldDescription(package private) static final AsyncProcessor.AsyncSubscription[]
(package private) Throwable
Write before updating subscribers, read after reading subscribers as TERMINATED.(package private) final AtomicReference
<AsyncProcessor.AsyncSubscription<T>[]> (package private) static final AsyncProcessor.AsyncSubscription[]
(package private) T
Write before updating subscribers, read after reading subscribers as TERMINATED. -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescription(package private) boolean
Tries to add the given subscriber to the subscribers array atomically or returns false if the processor has terminated.static <T> @NonNull AsyncProcessor
<T> create()
Creates a new AsyncProcessor.Returns the error that caused the FlowableProcessor to terminate or null if the FlowableProcessor hasn't terminated yet.getValue()
Returns a single value this processor currently has or null if no such value exists.boolean
Returns true if the FlowableProcessor has reached a terminal state through a complete event.boolean
Returns true if the FlowableProcessor has subscribers.boolean
Returns true if the FlowableProcessor has reached a terminal state through an error event.boolean
hasValue()
Returns true if this processor has any value.void
void
void
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
Atomically removes the given subscriber if it is subscribed to this processor.protected void
subscribeActual
(@NonNull org.reactivestreams.Subscriber<? super @NonNull T> s) 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
Methods inherited from class io.reactivex.rxjava3.core.Flowable
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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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Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Methods inherited from interface org.reactivestreams.Publisher
subscribe
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Field Details
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Constructor Details
-
AsyncProcessor
AsyncProcessor()Constructs an AsyncProcessor.- Since:
- 2.0
-
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Method Details
-
create
Creates a new AsyncProcessor.- Type Parameters:
T
- the value type to be received and emitted- Returns:
- the new AsyncProcessor instance
-
onSubscribe
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
. -
onNext
-
onError
-
onComplete
public void onComplete() -
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
-
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:
-
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:
-
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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subscribeActual
protected void subscribeActual(@NonNull @NonNull org.reactivestreams.Subscriber<? super @NonNull T> s) 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:
s
- the incomingSubscriber
, nevernull
-
add
Tries to add the given subscriber to the subscribers array atomically or returns false if the processor has terminated.- Parameters:
ps
- the subscriber to add- Returns:
- true if successful, false if the processor has terminated
-
remove
Atomically removes the given subscriber if it is subscribed to this processor.- Parameters:
ps
- the subscriber's subscription wrapper to remove
-
hasValue
Returns true if this processor has any value.The method is thread-safe.
- Returns:
- true if this processor has any value
-
getValue
Returns a single value this processor currently has or null if no such value exists.The method is thread-safe.
- Returns:
- a single value this processor currently has or null if no such value exists
-