/*
* 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
*
* 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 reactor.core.
CoreSubscriber;
/**
* Represents an never publisher which only calls onSubscribe.
* <p>
* This Publisher is effectively stateless and only a single instance exists.
* Use the {@link #instance()} method to obtain a properly type-parametrized view of it.
*
* @see <a href="https://github.com/reactor/reactive-streams-commons">Reactive-Streams-Commons</a>
*/
final class
MonoNever
extends
Mono<
Object> implements
SourceProducer<
Object> {
static final
Mono<
Object>
INSTANCE = new
MonoNever();
MonoNever() {
// deliberately no op
}
@
Override
public void
subscribe(
CoreSubscriber<? super
Object>
actual) {
actual.
onSubscribe(
Operators.
emptySubscription());
}
@
Override
public
Object scanUnsafe(
Attr key) {
return null; //no particular key to be represented, still useful in hooks
}
/**
* Returns a properly parametrized instance of this never Publisher.
*
* @param <T> the value type
* @return a properly parametrized instance of this never Publisher
*/
@
SuppressWarnings("unchecked")
static <T>
Mono<T>
instance() {
return (
Mono<T>)
INSTANCE;
}
}