reactor.core.publisher.FluxUsingWhen Maven / Gradle / Ivy
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/*
* Copyright (c) 2011-2018 Pivotal Software Inc, All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package reactor.core.publisher;
import java.util.Objects;
import java.util.concurrent.Callable;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
import java.util.function.Function;
import org.reactivestreams.Publisher;
import org.reactivestreams.Subscriber;
import org.reactivestreams.Subscription;
import reactor.core.CoreSubscriber;
import reactor.core.Exceptions;
import reactor.core.Fuseable.ConditionalSubscriber;
import reactor.core.publisher.Operators.DeferredSubscription;
import reactor.util.Loggers;
import reactor.util.annotation.Nullable;
import reactor.util.context.Context;
/**
* Uses a resource that is lazily generated by a {@link Publisher} for each individual{@link Subscriber},
* while streaming the values from a {@link Publisher} derived from the same resource.
* Whenever the resulting sequence terminates, the relevant {@link Function} generates
* a "cleanup" {@link Publisher} that is invoked but doesn't change the content of the
* main sequence. Instead it just defers the termination (unless it errors, in which case
* the error suppresses the original termination signal).
*
* Note that if the resource supplying {@link Publisher} emits more than one resource, the
* subsequent resources are dropped ({@link Operators#onNextDropped(Object, Context)}). If
* the publisher errors AFTER having emitted one resource, the error is also silently dropped
* ({@link Operators#onErrorDropped(Throwable, Context)}).
*
* @param the value type streamed
* @param the resource type
*/
final class FluxUsingWhen extends Flux implements SourceProducer {
final Publisher resourceSupplier;
final Function> resourceClosure;
final Function> asyncComplete;
final Function> asyncError;
@Nullable
final Function> asyncCancel;
FluxUsingWhen(Publisher resourceSupplier,
Function> resourceClosure,
Function> asyncComplete,
Function> asyncError,
@Nullable Function> asyncCancel) {
this.resourceSupplier = Objects.requireNonNull(resourceSupplier, "resourceSupplier");
this.resourceClosure = Objects.requireNonNull(resourceClosure, "resourceClosure");
this.asyncComplete = Objects.requireNonNull(asyncComplete, "asyncComplete");
this.asyncError = Objects.requireNonNull(asyncError, "asyncError");
this.asyncCancel = asyncCancel;
}
@Override
@SuppressWarnings("unchecked")
public void subscribe(CoreSubscriber actual) {
if (resourceSupplier instanceof Callable) {
try {
Callable resourceCallable = (Callable) resourceSupplier;
S resource = resourceCallable.call();
if (resource == null) {
Operators.complete(actual);
}
else {
Publisher p = deriveFluxFromResource(resource, resourceClosure);
UsingWhenSubscriber subscriber = prepareSubscriberForResource(resource,
actual,
asyncComplete,
asyncError,
asyncCancel,
null);
p.subscribe(subscriber);
}
}
catch (Throwable e) {
Operators.error(actual, e);
}
return;
}
//trigger the resource creation and delay the subscription to actual
resourceSupplier.subscribe(new ResourceSubscriber(actual, resourceClosure, asyncComplete, asyncError, asyncCancel, resourceSupplier instanceof Mono));
}
@Override
public Object scanUnsafe(Attr key) {
return null; //no particular key to be represented, still useful in hooks
}
private static Publisher deriveFluxFromResource(
RESOURCE resource,
Function> resourceClosure) {
Publisher p;
try {
p = Objects.requireNonNull(resourceClosure.apply(resource),
"The resourceClosure function returned a null value");
}
catch (Throwable e) {
p = Flux.error(e);
}
return p;
}
private static UsingWhenSubscriber prepareSubscriberForResource(
RESOURCE resource,
CoreSubscriber actual,
Function> asyncComplete,
Function> asyncError,
@Nullable Function> asyncCancel,
@Nullable DeferredSubscription arbiter) {
if (actual instanceof ConditionalSubscriber) {
@SuppressWarnings("unchecked")
ConditionalSubscriber conditionalActual = (ConditionalSubscriber) actual;
return new UsingWhenConditionalSubscriber<>(conditionalActual,
resource,
asyncComplete,
asyncError,
asyncCancel,
arbiter);
}
else {
return new UsingWhenSubscriber<>(actual,
resource,
asyncComplete,
asyncError,
asyncCancel,
arbiter);
}
}
static class ResourceSubscriber extends DeferredSubscription
implements InnerConsumer {
final CoreSubscriber actual;
final Function> resourceClosure;
final Function> asyncComplete;
final Function> asyncError;
@Nullable
final Function> asyncCancel;
final boolean isMonoSource;
Subscription resourceSubscription;
boolean resourceProvided;
UsingWhenSubscriber closureSubscriber;
ResourceSubscriber(CoreSubscriber actual,
Function> resourceClosure,
Function> asyncComplete,
Function> asyncError,
@Nullable Function> asyncCancel,
boolean isMonoSource) {
this.actual = Objects.requireNonNull(actual, "actual");
this.resourceClosure = Objects.requireNonNull(resourceClosure, "resourceClosure");
this.asyncComplete = Objects.requireNonNull(asyncComplete, "asyncComplete");
this.asyncError = Objects.requireNonNull(asyncError, "asyncError");
this.asyncCancel = asyncCancel;
this.isMonoSource = isMonoSource;
}
@Override
public void onNext(S resource) {
if (resourceProvided) {
Operators.onNextDropped(resource, actual.currentContext());
return;
}
resourceProvided = true;
final Publisher p = deriveFluxFromResource(resource, resourceClosure);
this.closureSubscriber = prepareSubscriberForResource(resource,
this.actual,
this.asyncComplete,
this.asyncError,
this.asyncCancel,
this);
p.subscribe(closureSubscriber);
if (!isMonoSource) {
resourceSubscription.cancel();
}
}
@Override
public Context currentContext() {
return actual.currentContext();
}
@Override
public void onError(Throwable throwable) {
if (resourceProvided) {
Operators.onErrorDropped(throwable, actual.currentContext());
return;
}
//even if no resource provided, actual.onSubscribe has been called
//let's immediately complete actual
actual.onError(throwable);
}
@Override
public void onComplete() {
if (resourceProvided) {
return;
}
//even if no resource provided, actual.onSubscribe has been called
//let's immediately complete actual
actual.onComplete();
}
@Override
public void onSubscribe(Subscription s) {
if (Operators.validate(this.resourceSubscription, s)) {
this.resourceSubscription = s;
actual.onSubscribe(this);
s.request(Long.MAX_VALUE);
}
}
@Override
public void cancel() {
if (!resourceProvided) {
resourceSubscription.cancel();
super.cancel();
}
else {
Operators.terminate(S, this);
if (closureSubscriber != null) {
closureSubscriber.cancel();
}
}
}
@Override
public Object scanUnsafe(Attr key) {
if (key == Attr.PARENT) return resourceSubscription;
if (key == Attr.ACTUAL) return actual;
if (key == Attr.PREFETCH) return Integer.MAX_VALUE;
if (key == Attr.TERMINATED) return resourceProvided;
return null;
}
}
static class UsingWhenSubscriber implements UsingWhenParent {
//state that differs in the different variants
final CoreSubscriber actual;
volatile Subscription s;
static final AtomicReferenceFieldUpdaterSUBSCRIPTION =
AtomicReferenceFieldUpdater.newUpdater(UsingWhenSubscriber.class,
Subscription.class, "s");
//rest of the state is always the same
final S resource;
final Function> asyncComplete;
final Function> asyncError;
@Nullable
final Function> asyncCancel;
@Nullable
final DeferredSubscription arbiter;
volatile int callbackApplied;
static final AtomicIntegerFieldUpdater CALLBACK_APPLIED = AtomicIntegerFieldUpdater.newUpdater(UsingWhenSubscriber.class, "callbackApplied");
/**
* Also stores the onComplete terminal state as {@link Exceptions#TERMINATED}
*/
Throwable error;
UsingWhenSubscriber(CoreSubscriber actual,
S resource,
Function> asyncComplete,
Function> asyncError,
@Nullable Function> asyncCancel,
@Nullable DeferredSubscription arbiter) {
this.actual = actual;
this.resource = resource;
this.asyncComplete = asyncComplete;
this.asyncError = asyncError;
this.asyncCancel = asyncCancel;
this.arbiter = arbiter;
}
@Override
public CoreSubscriber actual() {
return this.actual;
}
@Nullable
public Object scanUnsafe(Attr key) {
if (key == Attr.TERMINATED) return error != null;
if (key == Attr.ERROR) return (error == Exceptions.TERMINATED) ? null : error;
if (key == Attr.CANCELLED) return s == Operators.cancelledSubscription();
if (key == Attr.PARENT) return s;
return UsingWhenParent.super.scanUnsafe(key);
}
@Override
public void request(long l) {
if (Operators.validate(l)) {
s.request(l);
}
}
@Override
public void cancel() {
if (CALLBACK_APPLIED.compareAndSet(this, 0, 1)) {
if (Operators.terminate(SUBSCRIPTION, this)) {
try {
if (asyncCancel != null) {
Flux.from(asyncCancel.apply(resource))
.subscribe(new CancelInner(this));
}
else {
Flux.from(asyncComplete.apply(resource))
.subscribe(new CancelInner(this));
}
}
catch (Throwable error) {
Loggers.getLogger(FluxUsingWhen.class).warn("Error generating async resource cleanup during onCancel", error);
}
}
}
}
@Override
public void onNext(T t) {
actual.onNext(t);
}
@Override
public void onError(Throwable t) {
if (CALLBACK_APPLIED.compareAndSet(this, 0, 1)) {
Publisher p;
try {
p = Objects.requireNonNull(asyncError.apply(resource),
"The asyncError returned a null Publisher");
}
catch (Throwable e) {
Throwable _e = Operators.onOperatorError(e, actual.currentContext());
_e = Exceptions.addSuppressed(_e, t);
actual.onError(_e);
return;
}
p.subscribe(new RollbackInner(this, t));
}
}
@Override
public void onComplete() {
if (CALLBACK_APPLIED.compareAndSet(this, 0, 1)) {
Publisher p;
try {
p = Objects.requireNonNull(asyncComplete.apply(resource),
"The asyncComplete returned a null Publisher");
}
catch (Throwable e) {
Throwable _e = Operators.onOperatorError(e, actual.currentContext());
actual.onError(_e);
return;
}
p.subscribe(new CommitInner(this));
}
}
@Override
public void deferredComplete() {
this.error = Exceptions.TERMINATED;
this.actual.onComplete();
}
@Override
public void deferredError(Throwable error) {
this.error = error;
this.actual.onError(error);
}
@Override
public void onSubscribe(Subscription s) {
if (Operators.validate(this.s, s)) {
this.s = s;
if (arbiter == null) {
actual.onSubscribe(this);
}
else {
arbiter.set(s);
}
}
}
}
static final class UsingWhenConditionalSubscriber
extends UsingWhenSubscriber
implements ConditionalSubscriber {
final ConditionalSubscriber actual;
UsingWhenConditionalSubscriber(ConditionalSubscriber actual,
S resource,
Function> asyncComplete,
Function> asyncError,
@Nullable Function> asyncCancel,
@Nullable DeferredSubscription arbiter) {
super(actual, resource, asyncComplete, asyncError, asyncCancel, arbiter);
this.actual = actual;
}
@Override
public boolean tryOnNext(T t) {
return actual.tryOnNext(t);
}
}
static final class RollbackInner implements InnerConsumer