/*
 * 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.AtomicReferenceFieldUpdater;
import java.util.function.Function;
import java.util.stream.Stream;

import org.reactivestreams.Subscription;
import reactor.core.CoreSubscriber;
import reactor.core.Fuseable;
import reactor.core.Scannable;
import reactor.util.annotation.Nullable;
import reactor.util.context.Context;

Given a Mono source, applies a function on its single item and continues with that Mono instance, emitting its final result.
Type parameters:
  • <T> – the value type
See Also:
/** * Given a Mono source, applies a function on its single item and continues * with that Mono instance, emitting its final result. * * @param <T> the value type * * @see <a href="https://github.com/reactor/reactive-streams-commons">Reactive-Streams-Commons</a> */
final class MonoFlatMap<T, R> extends InternalMonoOperator<T, R> implements Fuseable { final Function<? super T, ? extends Mono<? extends R>> mapper; MonoFlatMap(Mono<? extends T> source, Function<? super T, ? extends Mono<? extends R>> mapper) { super(source); this.mapper = Objects.requireNonNull(mapper, "mapper"); } @Override public CoreSubscriber<? super T> subscribeOrReturn(CoreSubscriber<? super R> actual) { //for now Mono in general doesn't support onErrorContinue, so the scalar version shouldn't either if (FluxFlatMap.trySubscribeScalarMap(source, actual, mapper, true, false)) { return null; } FlatMapMain<T, R> manager = new FlatMapMain<>(actual, mapper); actual.onSubscribe(manager); return manager; } @Override public Object scanUnsafe(Attr key) { if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC; return super.scanUnsafe(key); } static final class FlatMapMain<T, R> extends Operators.MonoSubscriber<T, R> { final Function<? super T, ? extends Mono<? extends R>> mapper; final FlatMapInner<R> second; boolean done; volatile Subscription s; @SuppressWarnings("rawtypes") static final AtomicReferenceFieldUpdater<FlatMapMain, Subscription> S = AtomicReferenceFieldUpdater.newUpdater(FlatMapMain.class, Subscription.class, "s"); FlatMapMain(CoreSubscriber<? super R> subscriber, Function<? super T, ? extends Mono<? extends R>> mapper) { super(subscriber); this.mapper = mapper; this.second = new FlatMapInner<>(this); } @Override public Stream<? extends Scannable> inners() { return Stream.of(second); } @Override @Nullable public Object scanUnsafe(Attr key) { if (key == Attr.PARENT) return s; if (key == Attr.CANCELLED) return s == Operators.cancelledSubscription(); if (key == Attr.TERMINATED) return done; if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC; return super.scanUnsafe(key); } @Override public void onSubscribe(Subscription s) { if (Operators.setOnce(S, this, s)) { s.request(Long.MAX_VALUE); } } @Override public void onNext(T t) { if (done) { Operators.onNextDropped(t, actual.currentContext()); return; } done = true; Mono<? extends R> m; try { m = Objects.requireNonNull(mapper.apply(t), "The mapper returned a null Mono"); } catch (Throwable ex) { actual.onError(Operators.onOperatorError(s, ex, t, actual.currentContext())); return; } if (m instanceof Callable) { @SuppressWarnings("unchecked") Callable<R> c = (Callable<R>) m; R v; try { v = c.call(); } catch (Throwable ex) { actual.onError(Operators.onOperatorError(s, ex, t, actual.currentContext())); return; } if (v == null) { actual.onComplete(); } else { complete(v); } return; } try { m.subscribe(second); } catch (Throwable e) { actual.onError(Operators.onOperatorError(this, e, t, actual.currentContext())); } } @Override public void onError(Throwable t) { if (done) { Operators.onErrorDropped(t, actual.currentContext()); return; } done = true; actual.onError(t); } @Override public void onComplete() { if (done) { return; } done = true; actual.onComplete(); } @Override public void cancel() { super.cancel(); Operators.terminate(S, this); second.cancel(); } void secondError(Throwable ex) { actual.onError(ex); } void secondComplete() { actual.onComplete(); } } static final class FlatMapInner<R> implements InnerConsumer<R> { final FlatMapMain<?, R> parent; volatile Subscription s; @SuppressWarnings("rawtypes") static final AtomicReferenceFieldUpdater<FlatMapInner, Subscription> S = AtomicReferenceFieldUpdater.newUpdater(FlatMapInner.class, Subscription.class, "s"); boolean done; FlatMapInner(FlatMapMain<?, R> parent) { this.parent = parent; } @Override public Context currentContext() { return parent.currentContext(); } @Nullable @Override public Object scanUnsafe(Attr key) { if (key == Attr.PARENT) return s; if (key == Attr.ACTUAL) return parent; if (key == Attr.TERMINATED) return done; if (key == Attr.CANCELLED) return s == Operators.cancelledSubscription(); if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC; return null; } @Override public void onSubscribe(Subscription s) { if (Operators.setOnce(S, this, s)) { s.request(Long.MAX_VALUE); } } @Override public void onNext(R t) { if (done) { Operators.onNextDropped(t, parent.currentContext()); return; } done = true; this.parent.complete(t); } @Override public void onError(Throwable t) { if (done) { Operators.onErrorDropped(t, parent.currentContext()); return; } done = true; this.parent.secondError(t); } @Override public void onComplete() { if (done) { return; } done = true; this.parent.secondComplete(); } void cancel() { Operators.terminate(S, this); } } }