001/*
002 * Copyright 2002-2018 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.http.server.reactive;
018
019import java.util.concurrent.atomic.AtomicBoolean;
020
021import org.reactivestreams.Processor;
022import org.reactivestreams.Publisher;
023import reactor.core.publisher.Mono;
024
025import org.springframework.core.io.buffer.DataBuffer;
026import org.springframework.core.io.buffer.DataBufferFactory;
027import org.springframework.http.HttpHeaders;
028
029/**
030 * Abstract base class for listener-based server responses, e.g. Servlet 3.1
031 * and Undertow.
032 *
033 * @author Arjen Poutsma
034 * @since 5.0
035 */
036public abstract class AbstractListenerServerHttpResponse extends AbstractServerHttpResponse {
037
038        private final AtomicBoolean writeCalled = new AtomicBoolean();
039
040
041        public AbstractListenerServerHttpResponse(DataBufferFactory dataBufferFactory) {
042                super(dataBufferFactory);
043        }
044
045        public AbstractListenerServerHttpResponse(DataBufferFactory dataBufferFactory, HttpHeaders headers) {
046                super(dataBufferFactory, headers);
047        }
048
049
050        @Override
051        protected final Mono<Void> writeWithInternal(Publisher<? extends DataBuffer> body) {
052                return writeAndFlushWithInternal(Mono.just(body));
053        }
054
055        @Override
056        protected final Mono<Void> writeAndFlushWithInternal(
057                        Publisher<? extends Publisher<? extends DataBuffer>> body) {
058
059                if (this.writeCalled.compareAndSet(false, true)) {
060                        Processor<? super Publisher<? extends DataBuffer>, Void> processor = createBodyFlushProcessor();
061                        return Mono.from(subscriber -> {
062                                body.subscribe(processor);
063                                processor.subscribe(subscriber);
064                        });
065                }
066                return Mono.error(new IllegalStateException(
067                                "writeWith() or writeAndFlushWith() has already been called"));
068        }
069
070        /**
071         * Abstract template method to create a {@code Processor<Publisher<DataBuffer>, Void>}
072         * that will write the response body with flushes to the underlying output. Called from
073         * {@link #writeAndFlushWithInternal(Publisher)}.
074         */
075        protected abstract Processor<? super Publisher<? extends DataBuffer>, Void> createBodyFlushProcessor();
076
077}