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Create IterablePublisher to convert an Iterable to a Publisher (#5030)
* Implement the functionality to convert an Iterable to a Publisher * Use SimplePublisher in IterablePublisher * Remove unncessary lock
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‎.changes/next-release/feature-AWSSDKforJavav2-de94de6.json

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{
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"type": "feature",
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"category": "AWS SDK for Java v2",
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"contributor": "",
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"description": "Support creating an `SdkPublisher` from an `Iterable`"
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}

‎core/sdk-core/src/main/java/software/amazon/awssdk/core/async/SdkPublisher.java

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import software.amazon.awssdk.utils.async.EventListeningSubscriber;
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import software.amazon.awssdk.utils.async.FilteringSubscriber;
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import software.amazon.awssdk.utils.async.FlatteningSubscriber;
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import software.amazon.awssdk.utils.async.IterablePublisher;
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import software.amazon.awssdk.utils.async.LimitingSubscriber;
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import software.amazon.awssdk.utils.async.SequentialSubscriber;
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import software.amazon.awssdk.utils.internal.MappingSubscriber;
@@ -51,6 +52,17 @@ static <T> SdkPublisher<T> adapt(Publisher<T> toAdapt) {
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return toAdapt::subscribe;
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}
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/**
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* Create an {@link SdkPublisher} from an {@link Iterable}.
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*
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* @param iterable {@link Iterable} to adapt.
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* @param <T> Type of object being published.
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* @return SdkPublisher
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*/
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static <T> SdkPublisher<T> fromIterable(Iterable<T> iterable) {
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return adapt(new IterablePublisher<>(iterable));
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}
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/**
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* Filters published events to just those that are instances of the given class. This changes the type of
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* publisher to the type specified in the {@link Class}.

‎utils/pom.xml

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<scope>test</scope>
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<version>${slf4j.version}</version>
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</dependency>
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<dependency>
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<groupId>commons-lang</groupId>
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<artifactId>commons-lang</artifactId>
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<scope>test</scope>
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</dependency>
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</dependencies>
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<build>

‎utils/src/main/java/software/amazon/awssdk/utils/async/IterablePublisher.java

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/*
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* Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License").
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* You may not use this file except in compliance with the License.
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* A copy of the License is located at
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*
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* http://aws.amazon.com/apache2.0
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*
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* or in the "license" file accompanying this file. This file is distributed
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* on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
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* express or implied. See the License for the specific language governing
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* permissions and limitations under the License.
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*/
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package software.amazon.awssdk.utils.async;
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import java.util.Iterator;
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import org.reactivestreams.Publisher;
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import org.reactivestreams.Subscriber;
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import software.amazon.awssdk.annotations.SdkProtectedApi;
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import software.amazon.awssdk.utils.Validate;
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@SdkProtectedApi
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public class IterablePublisher<T> implements Publisher<T> {
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private final Iterable<T> iterable;
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public IterablePublisher(Iterable<T> iterable) {
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this.iterable = Validate.paramNotNull(iterable, "iterable");
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}
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@Override
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public void subscribe(Subscriber<? super T> subscriber) {
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Iterator<T> iterator = iterable.iterator();
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SimplePublisher<T> publisher = new SimplePublisher<>();
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// Prime the simple publisher with 1 event. More will be sent as these complete.
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sendEvent(iterator, publisher);
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publisher.subscribe(subscriber);
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}
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private void sendEvent(Iterator<T> iterator, SimplePublisher<T> publisher) {
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try {
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if (!iterator.hasNext()) {
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publisher.complete();
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return;
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}
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T next = iterator.next();
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if (next == null) {
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publisher.error(new IllegalArgumentException("Iterable returned null"));
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return;
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}
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publisher.send(next).whenComplete((v, t) -> {
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if (t != null) {
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publisher.error(t);
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} else {
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sendEvent(iterator, publisher);
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}
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});
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} catch (Throwable e) {
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publisher.error(e);
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}
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}
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}

‎utils/src/main/java/software/amazon/awssdk/utils/async/SimplePublisher.java

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@@ -278,7 +278,7 @@ private void doProcessQueue() {
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OnErrorQueueEntry<T> onErrorEntry = (OnErrorQueueEntry<T>) entry;
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failureMessage.trySet(() -> new IllegalStateException("onError() was already invoked.",
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onErrorEntry.failure));
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onErrorEntry.failure));
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log.trace(() -> "Calling onError() with " + onErrorEntry.failure, onErrorEntry.failure);
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subscriber.onError(onErrorEntry.failure);
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break;

‎utils/src/test/java/software/amazon/awssdk/utils/async/IterablePublisherTckTest.java

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/*
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* Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License").
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* You may not use this file except in compliance with the License.
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* A copy of the License is located at
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*
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* http://aws.amazon.com/apache2.0
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*
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* or in the "license" file accompanying this file. This file is distributed
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* on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
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* express or implied. See the License for the specific language governing
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* permissions and limitations under the License.
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*/
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package software.amazon.awssdk.utils.async;
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import java.util.Iterator;
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import org.reactivestreams.Publisher;
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import org.reactivestreams.tck.PublisherVerification;
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import org.reactivestreams.tck.TestEnvironment;
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public class IterablePublisherTckTest extends PublisherVerification<Long> {
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public IterablePublisherTckTest() {
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super(new TestEnvironment());
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}
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@Override
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public Publisher<Long> createPublisher(long elements) {
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Iterable<Long> iterable = () -> new Iterator<Long>() {
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private long count;
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@Override
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public boolean hasNext() {
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if (count == elements) {
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return false;
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}
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return true;
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}
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@Override
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public Long next() {
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count++;
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return count;
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}
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};
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return new IterablePublisher<>(iterable);
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}
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@Override
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public Publisher<Long> createFailedPublisher() {
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return null;
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}
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}

‎utils/src/test/java/software/amazon/awssdk/utils/async/IterablePublisherTest.java

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/*
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* Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License").
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* You may not use this file except in compliance with the License.
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* A copy of the License is located at
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*
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* http://aws.amazon.com/apache2.0
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*
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* or in the "license" file accompanying this file. This file is distributed
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* on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
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* express or implied. See the License for the specific language governing
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* permissions and limitations under the License.
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*/
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package software.amazon.awssdk.utils.async;
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import static org.assertj.core.api.Assertions.assertThat;
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import static org.assertj.core.api.Assertions.assertThatThrownBy;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.List;
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import java.util.stream.Collectors;
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import java.util.stream.IntStream;
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import org.apache.commons.lang.RandomStringUtils;
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import org.junit.jupiter.api.Test;
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import org.reactivestreams.Subscriber;
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import org.reactivestreams.Subscription;
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public class IterablePublisherTest {
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@Test
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void nullIterable_throwException() {
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assertThatThrownBy(() -> new IterablePublisher<>(null)).isInstanceOf(NullPointerException.class);
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}
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@Test
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void emptyIterable_shouldComplete() {
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TestSubscriber testSubscriber = new TestSubscriber();
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IterablePublisher<String> iterablePublisher = new IterablePublisher<>(new ArrayList<>());
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iterablePublisher.subscribe(testSubscriber);
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assertThat(testSubscriber.onCompleteInvoked).isTrue();
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assertThat(testSubscriber.onNextInvoked).isFalse();
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assertThat(testSubscriber.onErrorInvoked).isFalse();
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}
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@Test
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void iterableReturnNull_shouldInvokeOnError() {
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TestSubscriber testSubscriber = new TestSubscriber();
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IterablePublisher<String> iterablePublisher = new IterablePublisher<>(Arrays.asList("foo", null));
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iterablePublisher.subscribe(testSubscriber);
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assertThat(testSubscriber.onCompleteInvoked).isFalse();
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assertThat(testSubscriber.results).contains("foo");
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assertThat(testSubscriber.onErrorInvoked).isTrue();
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assertThat(testSubscriber.throwable).isInstanceOf(IllegalArgumentException.class).hasMessageContaining("returned null");
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}
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@Test
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void happyCase_shouldSendAllEvents() {
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TestSubscriber testSubscriber = new TestSubscriber();
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List<String> strings = IntStream.range(0, 100).mapToObj(i -> RandomStringUtils.random(i)).collect(Collectors.toList());
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IterablePublisher<String> iterablePublisher = new IterablePublisher<>(strings);
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iterablePublisher.subscribe(testSubscriber);
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assertThat(testSubscriber.onCompleteInvoked).isTrue();
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assertThat(testSubscriber.results).hasSameElementsAs(strings);
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assertThat(testSubscriber.onErrorInvoked).isFalse();
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}
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private static class TestSubscriber implements Subscriber<String> {
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private Subscription subscription;
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private List<String> results = new ArrayList<>();
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private boolean onNextInvoked;
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private boolean onErrorInvoked;
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private boolean onCompleteInvoked;
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private Throwable throwable;
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@Override
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public void onSubscribe(Subscription s) {
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this.subscription = s;
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s.request(1);
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}
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@Override
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public void onNext(String s) {
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onNextInvoked = true;
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results.add(s);
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subscription.request(1);
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}
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@Override
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public void onError(Throwable t) {
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onErrorInvoked = true;
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throwable = t;
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}
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@Override
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public void onComplete() {
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onCompleteInvoked = true;
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}
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}
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}

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