software.amazon.awssdk.utils.async.IterablePublisher 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.async;
import java.util.Iterator;
import org.reactivestreams.Publisher;
import org.reactivestreams.Subscriber;
import software.amazon.awssdk.annotations.SdkProtectedApi;
import software.amazon.awssdk.utils.Validate;
@SdkProtectedApi
public class IterablePublisher implements Publisher {
private final Iterable iterable;
public IterablePublisher(Iterable iterable) {
this.iterable = Validate.paramNotNull(iterable, "iterable");
}
@Override
public void subscribe(Subscriber subscriber) {
Iterator iterator = iterable.iterator();
SimplePublisher publisher = new SimplePublisher<>();
// Prime the simple publisher with 1 event. More will be sent as these complete.
sendEvent(iterator, publisher);
publisher.subscribe(subscriber);
}
private void sendEvent(Iterator iterator, SimplePublisher publisher) {
try {
if (!iterator.hasNext()) {
publisher.complete();
return;
}
T next = iterator.next();
if (next == null) {
publisher.error(new IllegalArgumentException("Iterable returned null"));
return;
}
publisher.send(next).whenComplete((v, t) -> {
if (t != null) {
publisher.error(t);
} else {
sendEvent(iterator, publisher);
}
});
} catch (Throwable e) {
publisher.error(e);
}
}
}