/*
 * 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.time.Duration;
import java.util.Objects;
import java.util.concurrent.Callable;

import reactor.core.CoreSubscriber;
import reactor.core.Exceptions;
import reactor.core.Fuseable;
import reactor.util.annotation.Nullable;

Executes a Callable function and emits a single value to each individual Subscriber.

Preferred to Supplier because the Callable may throw.

Type parameters:
  • <T> – the returned value type
See Also:
/** * Executes a Callable function and emits a single value to each individual Subscriber. * <p> * Preferred to {@link java.util.function.Supplier} because the Callable may throw. * * @param <T> the returned value type * @see <a href="https://github.com/reactor/reactive-streams-commons">Reactive-Streams-Commons</a> */
final class MonoCallable<T> extends Mono<T> implements Callable<T>, Fuseable, SourceProducer<T> { final Callable<? extends T> callable; MonoCallable(Callable<? extends T> callable) { this.callable = Objects.requireNonNull(callable, "callable"); } @Override public void subscribe(CoreSubscriber<? super T> actual) { Operators.MonoSubscriber<T, T> sds = new Operators.MonoSubscriber<>(actual); actual.onSubscribe(sds); if (sds.isCancelled()) { return; } try { T t = callable.call(); if (t == null) { sds.onComplete(); } else { sds.complete(t); } } catch (Throwable e) { actual.onError(Operators.onOperatorError(e, actual.currentContext())); } } @Override @Nullable public T block() { //duration is ignored below return block(Duration.ZERO); } @Override @Nullable public T block(Duration m) { try { return callable.call(); } catch (Throwable e) { throw Exceptions.propagate(e); } } @Override @Nullable public T call() throws Exception { return callable.call(); } @Override public Object scanUnsafe(Attr key) { if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC; return null; } }