org.springframework.integration.endpoint.ReactiveStreamsConsumer Maven / Gradle / Ivy
/*
* Copyright 2016-2020 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License 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 org.springframework.integration.endpoint;
import java.util.function.Consumer;
import org.reactivestreams.Publisher;
import org.reactivestreams.Subscriber;
import org.reactivestreams.Subscription;
import org.springframework.context.Lifecycle;
import org.springframework.integration.channel.ChannelUtils;
import org.springframework.integration.channel.NullChannel;
import org.springframework.integration.core.MessageProducer;
import org.springframework.integration.handler.ReactiveMessageHandlerAdapter;
import org.springframework.integration.router.MessageRouter;
import org.springframework.integration.util.IntegrationReactiveUtils;
import org.springframework.lang.Nullable;
import org.springframework.messaging.Message;
import org.springframework.messaging.MessageChannel;
import org.springframework.messaging.MessageHandler;
import org.springframework.messaging.ReactiveMessageHandler;
import org.springframework.util.Assert;
import org.springframework.util.ErrorHandler;
import reactor.core.CoreSubscriber;
import reactor.core.Disposable;
import reactor.core.publisher.Flux;
/**
* An {@link AbstractEndpoint} implementation for Reactive Streams subscription into an
* input channel and reactive consumption of messages from that channel.
*
* @author Artem Bilan
*
* @since 5.0
*/
public class ReactiveStreamsConsumer extends AbstractEndpoint implements IntegrationConsumer {
private final MessageChannel inputChannel;
private final Publisher> publisher;
private final MessageHandler handler;
@Nullable
private final ReactiveMessageHandler reactiveMessageHandler;
@Nullable
private final Subscriber> subscriber;
@Nullable
private final Lifecycle lifecycleDelegate;
private ErrorHandler errorHandler;
private volatile Disposable subscription;
@SuppressWarnings("unchecked")
public ReactiveStreamsConsumer(MessageChannel inputChannel, MessageHandler messageHandler) {
this(inputChannel,
messageHandler instanceof Subscriber
? (Subscriber>) messageHandler
: new MessageHandlerSubscriber(messageHandler));
}
public ReactiveStreamsConsumer(MessageChannel inputChannel, Subscriber> subscriber) {
Assert.notNull(inputChannel, "'inputChannel' must not be null");
Assert.notNull(subscriber, "'subscriber' must not be null");
this.inputChannel = inputChannel;
if (inputChannel instanceof NullChannel && logger.isWarnEnabled()) {
logger.warn("The consuming from the NullChannel does not have any effects: " +
"it doesn't forward messages sent to it. A NullChannel is the end of the flow.");
}
this.publisher = IntegrationReactiveUtils.messageChannelToFlux(inputChannel);
this.subscriber = subscriber;
this.lifecycleDelegate = subscriber instanceof Lifecycle ? (Lifecycle) subscriber : null;
if (subscriber instanceof MessageHandlerSubscriber) {
this.handler = ((MessageHandlerSubscriber) subscriber).messageHandler;
}
else if (subscriber instanceof MessageHandler) {
this.handler = (MessageHandler) subscriber;
}
else {
this.handler = this.subscriber::onNext;
}
this.reactiveMessageHandler = null;
}
/**
* Instantiate an endpoint based on the provided {@link MessageChannel} and {@link ReactiveMessageHandler}.
* @param inputChannel the channel to consume in reactive manner.
* @param reactiveMessageHandler the {@link ReactiveMessageHandler} to process messages.
* @since 5.3
*/
public ReactiveStreamsConsumer(MessageChannel inputChannel, ReactiveMessageHandler reactiveMessageHandler) {
Assert.notNull(inputChannel, "'inputChannel' must not be null");
this.inputChannel = inputChannel;
this.handler = new ReactiveMessageHandlerAdapter(reactiveMessageHandler);
this.reactiveMessageHandler = reactiveMessageHandler;
this.publisher = IntegrationReactiveUtils.messageChannelToFlux(inputChannel);
this.subscriber = null;
this.lifecycleDelegate =
reactiveMessageHandler instanceof Lifecycle ? (Lifecycle) reactiveMessageHandler : null;
}
public void setErrorHandler(ErrorHandler errorHandler) {
this.errorHandler = errorHandler;
}
@Override
public MessageChannel getInputChannel() {
return this.inputChannel;
}
@Override
public MessageChannel getOutputChannel() {
if (this.handler instanceof MessageProducer) {
return ((MessageProducer) this.handler).getOutputChannel();
}
else if (this.handler instanceof MessageRouter) {
return ((MessageRouter) this.handler).getDefaultOutputChannel();
}
else {
return null;
}
}
@Override
public MessageHandler getHandler() {
return this.handler;
}
@Override
protected void onInit() {
super.onInit();
if (this.errorHandler == null) {
this.errorHandler = ChannelUtils.getErrorHandler(getBeanFactory());
}
}
@Override
protected void doStart() {
if (this.lifecycleDelegate != null) {
this.lifecycleDelegate.start();
}
if (this.reactiveMessageHandler != null) {
this.subscription =
Flux.from(this.publisher)
.flatMap(this.reactiveMessageHandler::handleMessage)
.onErrorContinue((ex, data) -> this.errorHandler.handleError(ex))
.subscribe();
}
else if (this.subscriber != null) {
this.subscription =
Flux.from(this.publisher)
.subscribe((data) -> {
try {
this.subscriber.onNext(data);
}
catch (Exception ex) {
this.errorHandler.handleError(ex);
}
},
null,
this.subscriber::onComplete,
this.subscriber::onSubscribe);
}
}
@Override
protected void doStop() {
if (this.subscription != null) {
this.subscription.dispose();
}
if (this.lifecycleDelegate != null) {
this.lifecycleDelegate.stop();
}
}
private static final class MessageHandlerSubscriber
implements CoreSubscriber>, Disposable, Lifecycle {
private final Consumer> consumer;
private Subscription subscription;
private final MessageHandler messageHandler;
MessageHandlerSubscriber(MessageHandler messageHandler) {
Assert.notNull(messageHandler, "'messageHandler' must not be null");
this.messageHandler = messageHandler;
this.consumer = this.messageHandler::handleMessage;
}
@Override
public void onSubscribe(Subscription s) {
this.subscription = s;
s.request(Long.MAX_VALUE);
}
@Override
public void onNext(Message message) {
this.consumer.accept(message);
}
@Override
public void onError(Throwable t) {
}
@Override
public void onComplete() {
dispose();
}
@Override
public void dispose() {
Subscription s = this.subscription;
if (s != null) {
this.subscription = null;
s.cancel();
}
}
@Override
public boolean isDisposed() {
return this.subscription == null;
}
@Override
public void start() {
if (this.messageHandler instanceof Lifecycle) {
((Lifecycle) this.messageHandler).start();
}
}
@Override
public void stop() {
if (this.messageHandler instanceof Lifecycle) {
((Lifecycle) this.messageHandler).stop();
}
}
@Override
public boolean isRunning() {
return !(this.messageHandler instanceof Lifecycle) || ((Lifecycle) this.messageHandler).isRunning();
}
}
}