/*
 * Copyright (c) 2011-2017 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
 *
 *       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.Publisher;
import org.reactivestreams.Subscription;
import reactor.core.CoreSubscriber;
import reactor.core.Exceptions;
import reactor.core.Fuseable;
import reactor.util.annotation.Nullable;

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.

Type parameters:
  • <T> – the value type streamed
  • <S> – the resource type
See Also:
/** * 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. * <p> * <p> * 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 <T> the value type streamed * @param <S> the resource type * * @see <a href="https://github.com/reactor/reactive-streams-commons">Reactive-Streams-Commons</a> */
final class FluxUsing<T, S> extends Flux<T> implements Fuseable, SourceProducer<T> { final Callable<S> resourceSupplier; final Function<? super S, ? extends Publisher<? extends T>> sourceFactory; final Consumer<? super S> resourceCleanup; final boolean eager; FluxUsing(Callable<S> resourceSupplier, Function<? super S, ? extends Publisher<? extends T>> sourceFactory, Consumer<? super S> 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 @SuppressWarnings("unchecked") public void subscribe(CoreSubscriber<? super T> actual) { S resource; try { resource = resourceSupplier.call(); } catch (Throwable e) { Operators.error(actual, Operators.onOperatorError(e, actual.currentContext())); return; } Publisher<? extends T> p; try { p = Objects.requireNonNull(sourceFactory.apply(resource), "The sourceFactory returned a null value"); } catch (Throwable e) { Throwable _e = Operators.onOperatorError(e, actual.currentContext()); try { resourceCleanup.accept(resource); } catch (Throwable ex) { _e = Exceptions.addSuppressed(ex, _e); } Operators.error(actual, _e); return; } if (p instanceof Fuseable) { from(p).subscribe(new UsingFuseableSubscriber<>(actual, resourceCleanup, resource, eager)); } else if (actual instanceof ConditionalSubscriber) { from(p).subscribe(new UsingConditionalSubscriber<>((ConditionalSubscriber<? super T>) actual, resourceCleanup, resource, eager)); } else { from(p).subscribe(new UsingSubscriber<>(actual, resourceCleanup, resource, eager)); } } @Override public Object scanUnsafe(Attr key) { if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC; return null; } static final class UsingSubscriber<T, S> implements InnerOperator<T, T>, QueueSubscription<T> { final CoreSubscriber<? super T> actual; final Consumer<? super S> resourceCleanup; final S resource; final boolean eager; Subscription s; volatile int wip; @SuppressWarnings("rawtypes") static final AtomicIntegerFieldUpdater<UsingSubscriber> WIP = AtomicIntegerFieldUpdater.newUpdater(UsingSubscriber.class, "wip"); UsingSubscriber(CoreSubscriber<? super T> actual, Consumer<? super S> resourceCleanup, S resource, boolean eager) { this.actual = actual; this.resourceCleanup = resourceCleanup; this.resource = resource; this.eager = eager; } @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<? super T> 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()); } } @Override public void onSubscribe(Subscription s) { if (Operators.validate(this.s, s)) { this.s = s; actual.onSubscribe(this); } } @Override public void onNext(T t) { actual.onNext(t); } @Override public void onError(Throwable t) { 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 (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)) { cleanup(); } } @Override public int requestFusion(int requestedMode) { return NONE; // always reject, upstream turned out to be non-fuseable after all } @Override public void clear() { // ignoring fusion methods } @Override public boolean isEmpty() { // ignoring fusion methods return true; } @Override @Nullable public T poll() { return null; } @Override public int size() { return 0; } } static final class UsingFuseableSubscriber<T, S> implements InnerOperator<T, T>, QueueSubscription<T> { final CoreSubscriber<? super T> actual; final Consumer<? super S> resourceCleanup; final S resource; final boolean eager; QueueSubscription<T> s; volatile int wip; @SuppressWarnings("rawtypes") static final AtomicIntegerFieldUpdater<UsingFuseableSubscriber> WIP = AtomicIntegerFieldUpdater.newUpdater(UsingFuseableSubscriber.class, "wip"); int mode; UsingFuseableSubscriber(CoreSubscriber<? super T> actual, Consumer<? super S> resourceCleanup, S resource, boolean eager) { this.actual = actual; this.resourceCleanup = resourceCleanup; this.resource = resource; this.eager = eager; } @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<? super T> 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 = (QueueSubscription<T>) s; actual.onSubscribe(this); } } @Override public void onNext(T t) { actual.onNext(t); } @Override public void onError(Throwable t) { 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 (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)) { cleanup(); } } @Override public void clear() { s.clear(); } @Override public boolean isEmpty() { return s.isEmpty(); } @Override @Nullable public T poll() { T v = s.poll(); if (v == null && mode == SYNC) { if (WIP.compareAndSet(this, 0, 1)) { resourceCleanup.accept(resource); } } return v; } @Override public int requestFusion(int requestedMode) { int m = s.requestFusion(requestedMode); mode = m; return m; } @Override public int size() { return s.size(); } } static final class UsingConditionalSubscriber<T, S> implements ConditionalSubscriber<T>, InnerOperator<T, T>, QueueSubscription<T> { final ConditionalSubscriber<? super T> actual; final Consumer<? super S> resourceCleanup; final S resource; final boolean eager; Subscription s; volatile int wip; @SuppressWarnings("rawtypes") static final AtomicIntegerFieldUpdater<UsingConditionalSubscriber> WIP = AtomicIntegerFieldUpdater.newUpdater(UsingConditionalSubscriber.class, "wip"); UsingConditionalSubscriber(ConditionalSubscriber<? super T> actual, Consumer<? super S> resourceCleanup, S resource, boolean eager) { this.actual = actual; this.resourceCleanup = resourceCleanup; this.resource = resource; this.eager = eager; } @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<? super T> 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()); } } @Override public void onSubscribe(Subscription s) { if (Operators.validate(this.s, s)) { this.s = s; actual.onSubscribe(this); } } @Override public void onNext(T t) { actual.onNext(t); } @Override public boolean tryOnNext(T t) { return actual.tryOnNext(t); } @Override public void onError(Throwable t) { 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 (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)) { cleanup(); } } @Override public int requestFusion(int requestedMode) { return NONE; // always reject, upstream turned out to be non-fuseable after all } @Override public void clear() { // ignoring fusion methods } @Override public boolean isEmpty() { // ignoring fusion methods return true; } @Override @Nullable public T poll() { return null; } @Override public int size() { return 0; } } }