reactor.core.publisher.MonoUsing Maven / Gradle / Ivy
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/*
* Copyright (c) 2016-2023 VMware Inc. or its affiliates, 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
*
* https://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.function.Consumer;
import java.util.function.Function;
import org.reactivestreams.Subscription;
import reactor.core.CoreSubscriber;
import reactor.core.Exceptions;
import reactor.core.Fuseable;
import reactor.util.annotation.Nullable;
import reactor.util.context.Context;
/**
* Uses a resource, generated by a supplier for each individual Subscriber,
* while streaming the values from a
* Publisher derived from the same resource and makes sure the resource is released
* if the sequence terminates or the Subscriber cancels.
*
*
* Eager resource cleanup happens just before the source termination and exceptions
* raised by the cleanup Consumer may override the terminal event. Non-eager
* cleanup will drop any exception.
*
* @param the value type streamed
* @param the resource type
*
* @see Reactive-Streams-Commons
*/
final class MonoUsing extends Mono implements Fuseable, SourceProducer {
final Callable resourceSupplier;
final Function> sourceFactory;
final Consumer resourceCleanup;
final boolean eager;
MonoUsing(Callable resourceSupplier,
Function> sourceFactory,
Consumer resourceCleanup,
boolean eager) {
this.resourceSupplier =
Objects.requireNonNull(resourceSupplier, "resourceSupplier");
this.sourceFactory = Objects.requireNonNull(sourceFactory, "sourceFactory");
this.resourceCleanup = Objects.requireNonNull(resourceCleanup, "resourceCleanup");
this.eager = eager;
}
@Override
public void subscribe(CoreSubscriber actual) {
S resource;
try {
resource = resourceSupplier.call();
}
catch (Throwable e) {
Operators.error(actual, Operators.onOperatorError(e, actual.currentContext()));
return;
}
Mono p;
try {
p = Mono.fromDirect(Objects.requireNonNull(sourceFactory.apply(resource),
"The sourceFactory returned a null value"));
}
catch (Throwable e) {
try {
resourceCleanup.accept(resource);
}
catch (Throwable ex) {
e = Exceptions.addSuppressed(ex, Operators.onOperatorError(e, actual.currentContext()));
}
Operators.error(actual, Operators.onOperatorError(e, actual.currentContext()));
return;
}
if (p instanceof Fuseable) {
p.subscribe(new MonoUsingSubscriber<>(actual,
resourceCleanup,
resource,
eager,
true));
}
else {
p.subscribe(new MonoUsingSubscriber<>(actual,
resourceCleanup,
resource,
eager,
false));
}
}
@Override
public Object scanUnsafe(Attr key) {
if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC;
return SourceProducer.super.scanUnsafe(key);
}
static final class MonoUsingSubscriber
implements InnerOperator, QueueSubscription {
final CoreSubscriber actual;
final Consumer resourceCleanup;
final S resource;
final boolean eager;
final boolean allowFusion;
Subscription s;
@Nullable
QueueSubscription qs;
volatile int wip;
@SuppressWarnings("rawtypes")
static final AtomicIntegerFieldUpdater WIP =
AtomicIntegerFieldUpdater.newUpdater(MonoUsingSubscriber.class, "wip");
int mode;
boolean valued;
MonoUsingSubscriber(CoreSubscriber actual,
Consumer resourceCleanup,
S resource,
boolean eager,
boolean allowFusion) {
this.actual = actual;
this.resourceCleanup = resourceCleanup;
this.resource = resource;
this.eager = eager;
this.allowFusion = allowFusion;
}
@Override
@Nullable
public Object scanUnsafe(Attr key) {
if (key == Attr.TERMINATED || key == Attr.CANCELLED)
return wip == 1;
if (key == Attr.PARENT) return s;
if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC;
return InnerOperator.super.scanUnsafe(key);
}
@Override
public CoreSubscriber actual() {
return actual;
}
@Override
public void request(long n) {
s.request(n);
}
@Override
public void cancel() {
if (WIP.compareAndSet(this, 0, 1)) {
s.cancel();
cleanup();
}
}
void cleanup() {
try {
resourceCleanup.accept(resource);
}
catch (Throwable e) {
Operators.onErrorDropped(e, actual.currentContext());
}
}
@SuppressWarnings("unchecked")
@Override
public void onSubscribe(Subscription s) {
if (Operators.validate(this.s, s)) {
this.s = s;
if (s instanceof QueueSubscription) {
this.qs = (QueueSubscription) s;
}
actual.onSubscribe(this);
}
}
@Override
public void onNext(T t) {
if (mode == ASYNC) {
actual.onNext(null);
return;
}
this.valued = true;
if (eager && WIP.compareAndSet(this, 0, 1)) {
try {
resourceCleanup.accept(resource);
}
catch (Throwable e) {
Context ctx = actual.currentContext();
actual.onError(Operators.onOperatorError(e, ctx));
Operators.onDiscard(t, ctx);
return;
}
}
actual.onNext(t);
actual.onComplete();
if (!eager && WIP.compareAndSet(this, 0, 1)) {
try {
resourceCleanup.accept(resource);
}
catch (Throwable e) {
Operators.onErrorDropped(e, actual.currentContext());
}
}
}
@Override
public void onError(Throwable t) {
if (valued && mode != ASYNC) {
Operators.onErrorDropped(t, actual.currentContext());
return;
}
if (eager && WIP.compareAndSet(this, 0, 1)) {
try {
resourceCleanup.accept(resource);
}
catch (Throwable e) {
Throwable _e = Operators.onOperatorError(e, actual.currentContext());
t = Exceptions.addSuppressed(_e, t);
}
}
actual.onError(t);
if (!eager && WIP.compareAndSet(this, 0, 1)) {
cleanup();
}
}
@Override
public void onComplete() {
if (valued && mode != ASYNC) {
return;
}
//this should only happen in the empty case
if (eager && WIP.compareAndSet(this, 0, 1)) {
try {
resourceCleanup.accept(resource);
}
catch (Throwable e) {
actual.onError(Operators.onOperatorError(e, actual.currentContext()));
return;
}
}
actual.onComplete();
if (!eager && WIP.compareAndSet(this, 0, 1)) {
try {
resourceCleanup.accept(resource);
}
catch (Throwable e) {
Operators.onErrorDropped(e, actual.currentContext());
}
}
}
@Override
public void clear() {
if (qs != null) {
qs.clear();
}
}
@Override
public boolean isEmpty() {
return qs == null || qs.isEmpty();
}
@Override
@Nullable
public T poll() {
if (mode == NONE || qs == null) {
return null;
}
T v = qs.poll();
if (v != null) {
valued = true;
if (eager && WIP.compareAndSet(this, 0, 1)) {
try {
resourceCleanup.accept(resource); //throws upwards
}
catch (Throwable t) {
Operators.onDiscard(v, actual.currentContext());
throw t;
}
}
}
else if (mode == SYNC) {
if (!eager && WIP.compareAndSet(this, 0, 1)) {
try {
resourceCleanup.accept(resource);
}
catch (Throwable t) {
if (!valued) throw t;
else Operators.onErrorDropped(t, actual.currentContext());
//returns null, ie onComplete, in the second case
}
}
}
return v;
}
@Override
public int requestFusion(int requestedMode) {
if (qs == null) {
mode = NONE;
return NONE;
}
int m = qs.requestFusion(requestedMode);
mode = m;
return m;
}
@Override
public int size() {
if (qs == null) {
return 0;
}
return qs.size();
}
}
}