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AbstractSinglePublisher.java
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AbstractSinglePublisher.java
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/*
* Copyright (c) 2017-2022 the original author or authors.
*
* 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 org.eclipse.jetty.reactive.client.internal;
import java.util.Objects;
import java.util.concurrent.CancellationException;
import org.eclipse.jetty.util.thread.AutoLock;
import org.reactivestreams.Publisher;
import org.reactivestreams.Subscriber;
import org.reactivestreams.Subscription;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* A Publisher that supports a single Subscriber.
*
* @param <T> the type of items emitted by this Publisher
*/
public abstract class AbstractSinglePublisher<T> implements Publisher<T>, Subscription {
private static final Logger logger = LoggerFactory.getLogger(AbstractSinglePublisher.class);
private final AutoLock lock = new AutoLock();
private Subscriber<? super T> subscriber;
private boolean cancelled;
protected AutoLock lock() {
return lock.lock();
}
@Override
public void subscribe(Subscriber<? super T> subscriber) {
Objects.requireNonNull(subscriber, "invalid 'null' subscriber");
Throwable failure = null;
try (AutoLock ignored = lock()) {
if (this.subscriber != null) {
failure = new IllegalStateException("multiple subscribers not supported");
} else {
if (isCancelled()) {
failure = new CancellationException();
} else {
this.subscriber = subscriber;
}
}
}
if (logger.isDebugEnabled()) {
logger.debug("{} subscription from {}", this, subscriber);
}
subscriber.onSubscribe(this);
if (failure != null) {
onFailure(subscriber, failure);
}
}
protected Subscriber<? super T> subscriber() {
try (AutoLock ignored = lock()) {
return subscriber;
}
}
@Override
public void request(long n) {
Subscriber<? super T> subscriber;
Throwable failure = null;
try (AutoLock ignored = lock()) {
if (isCancelled()) {
return;
}
subscriber = subscriber();
if (n <= 0) {
failure = new IllegalArgumentException("reactive stream violation rule 3.9");
}
}
if (failure != null) {
onFailure(subscriber, failure);
} else {
onRequest(subscriber, n);
}
}
protected abstract void onRequest(Subscriber<? super T> subscriber, long n);
protected void onFailure(Subscriber<? super T> subscriber, Throwable failure) {
subscriber.onError(failure);
}
@Override
public void cancel() {
Subscriber<? super T> subscriber;
try (AutoLock ignored = lock()) {
cancelled = true;
subscriber = this.subscriber;
this.subscriber = null;
}
if (logger.isDebugEnabled()) {
logger.debug("{} cancelled subscription from {}", this, subscriber);
}
}
protected boolean isCancelled() {
try (AutoLock ignored = lock()) {
return cancelled;
}
}
@Override
public String toString() {
return String.format("%s@%x", getClass().getSimpleName(), hashCode());
}
}