001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.juneau.rest.server.reactive.reactor;
018
019import org.apache.juneau.rest.server.reactive.*;
020import org.reactivestreams.*;
021
022import io.reactivex.rxjava3.core.*;
023
024/**
025 * {@link ReactiveStreamsAdapter} for <a class="doclink" href="https://github.com/ReactiveX/RxJava">RxJava 3</a>
026 * return types.
027 *
028 * <ul>
029 *    <li>{@link Single Single&lt;T&gt;} &rarr; single value (via {@link Single#toCompletionStage()}).
030 *    <li>{@link Maybe Maybe&lt;T&gt;} &rarr; single value (via {@link Maybe#toCompletionStage(Object)} with a
031 *       {@code null} default, so an empty {@code Maybe} yields a {@code null} body).
032 *    <li>{@link Completable} &rarr; single {@code null} value (via {@link Completable#toCompletionStage(Object)}).
033 *    <li>{@link Flowable Flowable&lt;T&gt;} &rarr; stream (via {@link org.reactivestreams.FlowAdapters#toFlowPublisher(Publisher)}).
034 *    <li>{@link Observable Observable&lt;T&gt;} &rarr; stream (converted to a {@link Flowable} with
035 *       {@link BackpressureStrategy#BUFFER} first, since {@code Observable} has no native backpressure).
036 * </ul>
037 *
038 * @since 10.0.0
039 */
040public class RxJavaReactiveAdapter implements ReactiveStreamsAdapter {
041
042   @Override /* Overridden from ReactiveStreamsAdapter */
043   public boolean canAdapt(Object value) {
044      return value instanceof Single
045         || value instanceof Maybe
046         || value instanceof Completable
047         || value instanceof Flowable
048         || value instanceof Observable;
049   }
050
051   @Override /* Overridden from ReactiveStreamsAdapter */
052   public Adaptation adapt(Object value) {
053      if (value instanceof Single<?> value2)
054         return Adaptation.single(value2.toCompletionStage());
055      if (value instanceof Maybe<?> value2)
056         return Adaptation.single(value2.toCompletionStage(null));
057      if (value instanceof Completable value2)
058         return Adaptation.single(value2.toCompletionStage(null));
059      if (value instanceof Flowable<?> value2)
060         return Adaptation.stream(FlowAdapters.toFlowPublisher(value2));
061      var o = (Observable<?>) value;
062      return Adaptation.stream(FlowAdapters.toFlowPublisher(o.toFlowable(BackpressureStrategy.BUFFER)));
063   }
064}