software.amazon.awssdk.utils.internal.MappingSubscriber Maven / Gradle / Ivy
/*
* Copyright Amazon.com, Inc. or its affiliates. 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.
* A copy of the License is located at
*
* http://aws.amazon.com/apache2.0
*
* or in the "license" file accompanying this file. This file 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 software.amazon.awssdk.utils.internal;
import java.util.function.Function;
import org.reactivestreams.Subscriber;
import org.reactivestreams.Subscription;
import software.amazon.awssdk.annotations.SdkInternalApi;
/**
* Maps a subscriber of one type to another type. If an exception is thrown by the mapping function itself, the error
* will be propagated to the downstream subscriber as if it had come from the publisher and then the subscription will
* be implicitly cancelled and no further events from the publisher will be passed along.
*/
@SdkInternalApi
public class MappingSubscriber implements Subscriber {
private final Subscriber delegateSubscriber;
private final Function mapFunction;
private boolean isCancelled = false;
private Subscription subscription = null;
private MappingSubscriber(Subscriber delegateSubscriber,
Function mapFunction) {
this.delegateSubscriber = delegateSubscriber;
this.mapFunction = mapFunction;
}
public static MappingSubscriber create(Subscriber subscriber,
Function mapFunction) {
return new MappingSubscriber<>(subscriber, mapFunction);
}
@Override
public void onSubscribe(Subscription subscription) {
this.subscription = subscription;
delegateSubscriber.onSubscribe(subscription);
}
@Override
public void onError(Throwable throwable) {
if (!isCancelled) {
delegateSubscriber.onError(throwable);
}
}
@Override
public void onComplete() {
if (!isCancelled) {
delegateSubscriber.onComplete();
}
}
@Override
public void onNext(T t) {
if (!isCancelled) {
try {
delegateSubscriber.onNext(mapFunction.apply(t));
} catch (RuntimeException e) {
// If the map function throws an exception, the subscription should be cancelled as the publisher will
// otherwise not be aware it has happened and should have the opportunity to clean up resources.
cancelSubscriptions();
delegateSubscriber.onError(e);
}
}
}
private void cancelSubscriptions() {
this.isCancelled = true;
if (this.subscription != null) {
try {
this.subscription.cancel();
} catch (RuntimeException ignored) {
// ignore exceptions
}
}
}
}