Class AsyncProcessor<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.AsyncProcessor<T>
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- Type Parameters:
T
- the value type
- All Implemented Interfaces:
FlowableSubscriber<T>
,org.reactivestreams.Processor<T,T>
,org.reactivestreams.Publisher<T>
,org.reactivestreams.Subscriber<T>
public final class AsyncProcessor<@NonNull T> extends FlowableProcessor<T>
Processor that emits the very last value followed by a completion event or the received error toSubscriber
s.This processor does not have a public constructor by design; a new empty instance of this
AsyncProcessor
can be created via thecreate()
method.Since an
AsyncProcessor
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.AsyncProcessor
is aFlowable
as well as aFlowableProcessor
and supports backpressure from the downstream but itsSubscriber
-side consumes items in an unbounded manner.When this
AsyncProcessor
is terminated viaonError(Throwable)
, the last observed item (if any) is cleared and lateSubscriber
s only receive theonError
event.The
AsyncProcessor
caches the latest item internally and it emits this item only whenonComplete
is called. Therefore, it is not recommended to use thisProcessor
with infinite or never-completing sources.Even though
AsyncProcessor
implements theSubscriber
interface, callingonSubscribe
is not required (Rule 2.12) if the processor is used as a standalone source. However, callingonSubscribe
after theAsyncProcessor
reached its terminal state will result in the givenSubscription
being canceled immediately.Calling
onNext(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). The implementation ofonXXX
methods are technically thread-safe but non-serialized calls to them may lead to undefined state in the currently subscribedSubscriber
s.This
AsyncProcessor
supports the standard state-peeking methodshasComplete()
,hasThrowable()
,getThrowable()
andhasSubscribers()
as well as means to read the very last observed value - after thisAsyncProcessor
has been completed - in a non-blocking and thread-safe manner viahasValue()
orgetValue()
.- 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 Classes Modifier and Type Class Description (package private) static class
AsyncProcessor.AsyncSubscription<T>
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Field Summary
Fields Modifier and Type Field Description (package private) static AsyncProcessor.AsyncSubscription[]
EMPTY
(package private) java.lang.Throwable
error
Write before updating subscribers, read after reading subscribers as TERMINATED.(package private) java.util.concurrent.atomic.AtomicReference<AsyncProcessor.AsyncSubscription<T>[]>
subscribers
(package private) static AsyncProcessor.AsyncSubscription[]
TERMINATED
(package private) T
value
Write before updating subscribers, read after reading subscribers as TERMINATED.
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Constructor Summary
Constructors Constructor Description AsyncProcessor()
Constructs an AsyncProcessor.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description (package private) boolean
add(AsyncProcessor.AsyncSubscription<@NonNull T> ps)
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.@Nullable java.lang.Throwable
getThrowable()
Returns the error that caused the FlowableProcessor to terminate or null if the FlowableProcessor hasn't terminated yet.T
getValue()
Returns a single value this processor currently has or null if no such value exists.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
hasValue()
Returns true if this processor has any value.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(AsyncProcessor.AsyncSubscription<@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> s)
Operator implementations (both source and intermediate) should implement this method that performs the necessary business logic and handles the incomingSubscriber
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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, throttleWithTimeout, throttleWithTimeout, throttleWithTimeout, timeInterval, timeInterval, timeInterval, timeInterval, timeout, timeout, timeout, timeout, timeout, timeout, timeout, timeout, timer, timer, timestamp, timestamp, timestamp, timestamp, to, toFuture, toList, toList, toList, toMap, toMap, toMap, toMultimap, toMultimap, toMultimap, toMultimap, toObservable, toSortedList, toSortedList, toSortedList, toSortedList, unsafeCreate, unsubscribeOn, using, using, window, window, window, window, window, window, window, window, window, window, window, window, window, window, window, window, window, withLatestFrom, withLatestFrom, withLatestFrom, withLatestFrom, withLatestFrom, withLatestFrom, zip, zip, zip, zip, zip, zip, zip, zip, zip, zip, zip, zip, zipArray, zipWith, zipWith, zipWith, zipWith
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Field Detail
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EMPTY
static final AsyncProcessor.AsyncSubscription[] EMPTY
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TERMINATED
static final AsyncProcessor.AsyncSubscription[] TERMINATED
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subscribers
final java.util.concurrent.atomic.AtomicReference<AsyncProcessor.AsyncSubscription<T>[]> subscribers
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error
java.lang.Throwable error
Write before updating subscribers, read after reading subscribers as TERMINATED.
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value
T value
Write before updating subscribers, read after reading subscribers as TERMINATED.
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Method Detail
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create
@CheckReturnValue @NonNull public static <T> @NonNull AsyncProcessor<T> create()
Creates a new AsyncProcessor.- Type Parameters:
T
- the value type to be received and emitted- Returns:
- the new AsyncProcessor instance
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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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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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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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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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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
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add
boolean add(AsyncProcessor.AsyncSubscription<@NonNull T> ps)
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
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remove
void remove(AsyncProcessor.AsyncSubscription<@NonNull T> ps)
Atomically removes the given subscriber if it is subscribed to this processor.- Parameters:
ps
- the subscriber's subscription wrapper to remove
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hasValue
@CheckReturnValue public boolean hasValue()
Returns true if this processor has any value.The method is thread-safe.
- Returns:
- true if this processor has any value
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getValue
@Nullable @CheckReturnValue public T 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
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