Support Reactor Netty 2 / Netty 5 in spring-messaging

Closes gh-28847

spring-messaging/spring-messaging.gradle

@@ -9,6 +9,7 @@ dependencies {
 	optional(project(":spring-context"))
 	optional(project(":spring-oxm"))
 	optional("io.projectreactor.netty:reactor-netty-http")
+	optional("io.projectreactor.netty:reactor-netty5-http:2.0.0-M1")
 	optional("io.rsocket:rsocket-core")
 	optional("io.rsocket:rsocket-transport-netty")
 	optional("com.fasterxml.jackson.core:jackson-databind")

spring-messaging/src/main/java/org/springframework/messaging/simp/stomp/ReactorNettyTcpStompClient.java

@@ -21,17 +21,31 @@ import java.util.concurrent.CompletableFuture;
 import org.springframework.lang.Nullable;
 import org.springframework.messaging.simp.SimpLogging;
 import org.springframework.messaging.tcp.TcpOperations;
+import org.springframework.messaging.tcp.reactor.ReactorNetty2TcpClient;
 import org.springframework.messaging.tcp.reactor.ReactorNettyTcpClient;
 import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
 
 /**
- * A STOMP over TCP client that uses {@link ReactorNettyTcpClient}.
+ * A STOMP over TCP client, configurable with either
+ * {@link ReactorNettyTcpClient} or {@link ReactorNetty2TcpClient}.
  *
  * @author Rossen Stoyanchev
  * @since 5.0
  */
 public class ReactorNettyTcpStompClient extends StompClientSupport {
 
+	private static final boolean reactorNettyClientPresent;
+
+	private static final boolean reactorNetty2ClientPresent;
+
+	static {
+		ClassLoader classLoader = StompBrokerRelayMessageHandler.class.getClassLoader();
+		reactorNettyClientPresent = ClassUtils.isPresent("reactor.netty.http.client.HttpClient", classLoader);
+		reactorNetty2ClientPresent = ClassUtils.isPresent("reactor.netty5.http.client.HttpClient", classLoader);
+	}
+
+
 	private final TcpOperations<byte[]> tcpClient;
 
 
@@ -60,10 +74,18 @@ public class ReactorNettyTcpStompClient extends StompClientSupport {
 		this.tcpClient = tcpClient;
 	}
 
-	private static ReactorNettyTcpClient<byte[]> initTcpClient(String host, int port) {
-		ReactorNettyTcpClient<byte[]> client = new ReactorNettyTcpClient<>(host, port, new StompReactorNettyCodec());
-		client.setLogger(SimpLogging.forLog(client.getLogger()));
-		return client;
+	private static TcpOperations<byte[]> initTcpClient(String host, int port) {
+		if (reactorNettyClientPresent) {
+			ReactorNettyTcpClient<byte[]> client = new ReactorNettyTcpClient<>(host, port, new StompReactorNettyCodec());
+			client.setLogger(SimpLogging.forLog(client.getLogger()));
+			return client;
+		}
+		else if (reactorNetty2ClientPresent) {
+			ReactorNetty2TcpClient<byte[]> client = new ReactorNetty2TcpClient<>(host, port, new StompTcpMessageCodec());
+			client.setLogger(SimpLogging.forLog(client.getLogger()));
+			return client;
+		}
+		throw new IllegalStateException("No compatible version of Reactor Netty");
 	}
 
 

spring-messaging/src/main/java/org/springframework/messaging/simp/stomp/StompBrokerRelayMessageHandler.java

@@ -43,10 +43,13 @@ import org.springframework.messaging.support.MessageHeaderInitializer;
 import org.springframework.messaging.tcp.FixedIntervalReconnectStrategy;
 import org.springframework.messaging.tcp.TcpConnection;
 import org.springframework.messaging.tcp.TcpOperations;
+import org.springframework.messaging.tcp.reactor.ReactorNetty2TcpClient;
 import org.springframework.messaging.tcp.reactor.ReactorNettyCodec;
 import org.springframework.messaging.tcp.reactor.ReactorNettyTcpClient;
+import org.springframework.messaging.tcp.reactor.TcpMessageCodec;
 import org.springframework.scheduling.TaskScheduler;
 import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
 
 /**
  * A {@link org.springframework.messaging.MessageHandler} that handles messages by
@@ -101,10 +104,18 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler
 
 	private static final Message<byte[]> HEARTBEAT_MESSAGE;
 
+	private static final boolean reactorNettyClientPresent;
+
+	private static final boolean reactorNetty2ClientPresent;
+
 	static {
 		HEART_BEAT_ACCESSOR = StompHeaderAccessor.createForHeartbeat();
 		HEARTBEAT_MESSAGE = MessageBuilder.createMessage(
 				StompDecoder.HEARTBEAT_PAYLOAD, HEART_BEAT_ACCESSOR.getMessageHeaders());
+
+		ClassLoader classLoader = StompBrokerRelayMessageHandler.class.getClassLoader();
+		reactorNettyClientPresent = ClassUtils.isPresent("reactor.netty.http.client.HttpClient", classLoader);
+		reactorNetty2ClientPresent = ClassUtils.isPresent("reactor.netty5.http.client.HttpClient", classLoader);
 	}
 
 
@@ -345,7 +356,8 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler
 
 	/**
 	 * Configure a TCP client for managing TCP connections to the STOMP broker.
-	 * <p>By default {@link ReactorNettyTcpClient} is used.
+	 * <p>By default {@link ReactorNettyTcpClient} or
+	 * {@link ReactorNetty2TcpClient} is used.
 	 * <p><strong>Note:</strong> when this property is used, any
 	 * {@link #setRelayHost(String) host} or {@link #setRelayPort(int) port}
 	 * specified are effectively ignored.
@@ -458,15 +470,24 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler
 		}
 	}
 
-	private ReactorNettyTcpClient<byte[]> initTcpClient() {
+	private TcpOperations<byte[]> initTcpClient() {
 		StompDecoder decoder = new StompDecoder();
 		if (this.headerInitializer != null) {
 			decoder.setHeaderInitializer(this.headerInitializer);
 		}
-		ReactorNettyCodec<byte[]> codec = new StompReactorNettyCodec(decoder);
-		ReactorNettyTcpClient<byte[]> client = new ReactorNettyTcpClient<>(this.relayHost, this.relayPort, codec);
-		client.setLogger(SimpLogging.forLog(client.getLogger()));
-		return client;
+		if (reactorNettyClientPresent) {
+			ReactorNettyCodec<byte[]> codec = new StompReactorNettyCodec(decoder);
+			ReactorNettyTcpClient<byte[]> client = new ReactorNettyTcpClient<>(this.relayHost, this.relayPort, codec);
+			client.setLogger(SimpLogging.forLog(client.getLogger()));
+			return client;
+		}
+		else if (reactorNetty2ClientPresent) {
+			TcpMessageCodec<byte[]> codec = new StompTcpMessageCodec(decoder);
+			ReactorNetty2TcpClient<byte[]> client = new ReactorNetty2TcpClient<>(this.relayHost, this.relayPort, codec);
+			client.setLogger(SimpLogging.forLog(client.getLogger()));
+			return client;
+		}
+		throw new IllegalStateException("No compatible version of Reactor Netty");
 	}
 
 	@Override

spring-messaging/src/main/java/org/springframework/messaging/simp/stomp/StompTcpMessageCodec.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2002-2022 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.messaging.simp.stomp;
+
+import java.nio.ByteBuffer;
+import java.util.List;
+
+import org.springframework.messaging.Message;
+import org.springframework.messaging.tcp.reactor.TcpMessageCodec;
+
+/**
+ * {@link TcpMessageCodec} for STOMP, delegating to {@link StompDecoder} and
+ * {@link StompEncoder}.
+ *
+ * @author Rossen Stoyanchev
+ * @since 6.0
+ */
+public class StompTcpMessageCodec implements TcpMessageCodec<byte[]> {
+
+	private final StompDecoder decoder;
+
+	private final StompEncoder encoder;
+
+
+	public StompTcpMessageCodec() {
+		this(new StompDecoder());
+	}
+
+	public StompTcpMessageCodec(StompDecoder decoder) {
+		this(decoder, new StompEncoder());
+	}
+
+	public StompTcpMessageCodec(StompDecoder decoder, StompEncoder encoder) {
+		this.decoder = decoder;
+		this.encoder = encoder;
+	}
+
+
+	@Override
+	public List<Message<byte[]>> decode(ByteBuffer nioBuffer) {
+		return this.decoder.decode(nioBuffer);
+	}
+
+	@Override
+	public ByteBuffer encode(Message<byte[]> message) {
+		return ByteBuffer.wrap(this.encoder.encode(message));
+	}
+
+}

spring-messaging/src/main/java/org/springframework/messaging/tcp/reactor/ReactorNetty2TcpClient.java

@@ -0,0 +1,352 @@
+/*
+ * Copyright 2002-2022 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.messaging.tcp.reactor;
+
+import java.nio.ByteBuffer;
+import java.time.Duration;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+
+import io.netty5.buffer.api.Buffer;
+import io.netty5.channel.ChannelHandlerContext;
+import io.netty5.channel.group.ChannelGroup;
+import io.netty5.channel.group.DefaultChannelGroup;
+import io.netty5.handler.codec.ByteToMessageDecoder;
+import io.netty5.util.concurrent.ImmediateEventExecutor;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.reactivestreams.Publisher;
+import reactor.core.publisher.Mono;
+import reactor.core.publisher.Sinks;
+import reactor.core.scheduler.Scheduler;
+import reactor.core.scheduler.Schedulers;
+import reactor.netty5.Connection;
+import reactor.netty5.NettyInbound;
+import reactor.netty5.NettyOutbound;
+import reactor.netty5.resources.ConnectionProvider;
+import reactor.netty5.resources.LoopResources;
+import reactor.netty5.tcp.TcpClient;
+import reactor.util.retry.Retry;
+
+import org.springframework.lang.Nullable;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.tcp.ReconnectStrategy;
+import org.springframework.messaging.tcp.TcpConnection;
+import org.springframework.messaging.tcp.TcpConnectionHandler;
+import org.springframework.messaging.tcp.TcpOperations;
+import org.springframework.util.Assert;
+
+/**
+ * Reactor Netty based implementation of {@link TcpOperations}.
+ *
+ * <p>This class is based on {@link ReactorNettyTcpClient}.
+ *
+ * @author Rossen Stoyanchev
+ * @since 6.0
+ * @param <P> the type of payload for in and outbound messages
+ */
+public class ReactorNetty2TcpClient<P> implements TcpOperations<P> {
+
+	private static final int PUBLISH_ON_BUFFER_SIZE = 16;
+
+
+	private final TcpClient tcpClient;
+
+	private final TcpMessageCodec<P> codec;
+
+	@Nullable
+	private final ChannelGroup channelGroup;
+
+	@Nullable
+	private final LoopResources loopResources;
+
+	@Nullable
+	private final ConnectionProvider poolResources;
+
+	private final Scheduler scheduler = Schedulers.newParallel("tcp-client-scheduler");
+
+	private Log logger = LogFactory.getLog(ReactorNetty2TcpClient.class);
+
+	private volatile boolean stopping;
+
+
+	/**
+	 * Simple constructor with the host and port to use to connect to.
+	 * <p>This constructor manages the lifecycle of the {@link TcpClient} and
+	 * underlying resources such as {@link ConnectionProvider},
+	 * {@link LoopResources}, and {@link ChannelGroup}.
+	 * <p>For full control over the initialization and lifecycle of the
+	 * TcpClient, use {@link #ReactorNetty2TcpClient(TcpClient, TcpMessageCodec)}.
+	 * @param host the host to connect to
+	 * @param port the port to connect to
+	 * @param codec for encoding and decoding the input/output byte streams
+	 * @see org.springframework.messaging.simp.stomp.StompReactorNettyCodec
+	 */
+	public ReactorNetty2TcpClient(String host, int port, TcpMessageCodec<P> codec) {
+		Assert.notNull(host, "host is required");
+		Assert.notNull(codec, "ReactorNettyCodec is required");
+
+		this.channelGroup = new DefaultChannelGroup(ImmediateEventExecutor.INSTANCE);
+		this.loopResources = LoopResources.create("tcp-client-loop");
+		this.poolResources = ConnectionProvider.create("tcp-client-pool", 10000);
+		this.codec = codec;
+
+		this.tcpClient = TcpClient.create(this.poolResources)
+				.host(host).port(port)
+				.runOn(this.loopResources, false)
+				.doOnConnected(conn -> this.channelGroup.add(conn.channel()));
+	}
+
+	/**
+	 * A variant of {@link #ReactorNetty2TcpClient(String, int, TcpMessageCodec)}
+	 * that still manages the lifecycle of the {@link TcpClient} and underlying
+	 * resources, but allows for direct configuration of other properties of the
+	 * client through a {@code Function<TcpClient, TcpClient>}.
+	 * @param clientConfigurer the configurer function
+	 * @param codec for encoding and decoding the input/output byte streams
+	 * @since 5.1.3
+	 * @see org.springframework.messaging.simp.stomp.StompReactorNettyCodec
+	 */
+	public ReactorNetty2TcpClient(Function<TcpClient, TcpClient> clientConfigurer, TcpMessageCodec<P> codec) {
+		Assert.notNull(codec, "ReactorNettyCodec is required");
+
+		this.channelGroup = new DefaultChannelGroup(ImmediateEventExecutor.INSTANCE);
+		this.loopResources = LoopResources.create("tcp-client-loop");
+		this.poolResources = ConnectionProvider.create("tcp-client-pool", 10000);
+		this.codec = codec;
+
+		this.tcpClient = clientConfigurer.apply(TcpClient
+				.create(this.poolResources)
+				.runOn(this.loopResources, false)
+				.doOnConnected(conn -> this.channelGroup.add(conn.channel())));
+	}
+
+	/**
+	 * Constructor with an externally created {@link TcpClient} instance whose
+	 * lifecycle is expected to be managed externally.
+	 * @param tcpClient the TcpClient instance to use
+	 * @param codec for encoding and decoding the input/output byte streams
+	 * @see org.springframework.messaging.simp.stomp.StompReactorNettyCodec
+	 */
+	public ReactorNetty2TcpClient(TcpClient tcpClient, TcpMessageCodec<P> codec) {
+		Assert.notNull(tcpClient, "TcpClient is required");
+		Assert.notNull(codec, "ReactorNettyCodec is required");
+		this.tcpClient = tcpClient;
+		this.codec = codec;
+
+		this.channelGroup = null;
+		this.loopResources = null;
+		this.poolResources = null;
+	}
+
+
+	/**
+	 * Set an alternative logger to use than the one based on the class name.
+	 * @param logger the logger to use
+	 * @since 5.1
+	 */
+	public void setLogger(Log logger) {
+		this.logger = logger;
+	}
+
+	/**
+	 * Return the currently configured Logger.
+	 * @since 5.1
+	 */
+	public Log getLogger() {
+		return logger;
+	}
+
+
+	@Override
+	public CompletableFuture<Void> connectAsync(TcpConnectionHandler<P> handler) {
+		Assert.notNull(handler, "TcpConnectionHandler is required");
+
+		if (this.stopping) {
+			return handleShuttingDownConnectFailure(handler);
+		}
+
+		return extendTcpClient(this.tcpClient, handler)
+				.handle(new ReactorNettyHandler(handler))
+				.connect()
+				.doOnError(handler::afterConnectFailure)
+				.then().toFuture();
+	}
+
+	/**
+	 * Provides an opportunity to initialize the {@link TcpClient} for the given
+	 * {@link TcpConnectionHandler} which may implement sub-interfaces such as
+	 * {@link org.springframework.messaging.simp.stomp.StompTcpConnectionHandler}
+	 * that expose further information.
+	 * @param tcpClient the candidate TcpClient
+	 * @param handler the handler for the TCP connection
+	 * @return the same handler or an updated instance
+	 */
+	protected TcpClient extendTcpClient(TcpClient tcpClient, TcpConnectionHandler<P> handler) {
+		return tcpClient;
+	}
+
+	@Override
+	public CompletableFuture<Void> connectAsync(TcpConnectionHandler<P> handler, ReconnectStrategy strategy) {
+		Assert.notNull(handler, "TcpConnectionHandler is required");
+		Assert.notNull(strategy, "ReconnectStrategy is required");
+
+		if (this.stopping) {
+			return handleShuttingDownConnectFailure(handler);
+		}
+
+		// Report first connect to the ListenableFuture
+		CompletableFuture<Void> connectFuture = new CompletableFuture<>();
+
+		extendTcpClient(this.tcpClient, handler)
+				.handle(new ReactorNettyHandler(handler))
+				.connect()
+				.doOnNext(conn -> connectFuture.complete(null))
+				.doOnError(connectFuture::completeExceptionally)
+				.doOnError(handler::afterConnectFailure)    // report all connect failures to the handler
+				.flatMap(Connection::onDispose)             // post-connect issues
+				.retryWhen(Retry.from(signals -> signals
+						.map(retrySignal -> (int) retrySignal.totalRetriesInARow())
+						.flatMap(attempt -> reconnect(attempt, strategy))))
+				.repeatWhen(flux -> flux
+						.scan(1, (count, element) -> count++)
+						.flatMap(attempt -> reconnect(attempt, strategy)))
+				.subscribe();
+		return connectFuture;
+	}
+
+	private CompletableFuture<Void> handleShuttingDownConnectFailure(TcpConnectionHandler<P> handler) {
+		IllegalStateException ex = new IllegalStateException("Shutting down.");
+		handler.afterConnectFailure(ex);
+		return Mono.<Void>error(ex).toFuture();
+	}
+
+	private Publisher<? extends Long> reconnect(Integer attempt, ReconnectStrategy reconnectStrategy) {
+		Long time = reconnectStrategy.getTimeToNextAttempt(attempt);
+		return (time != null ? Mono.delay(Duration.ofMillis(time), this.scheduler) : Mono.empty());
+	}
+
+	@Override
+	public CompletableFuture<Void> shutdownAsync() {
+		if (this.stopping) {
+			return CompletableFuture.completedFuture(null);
+		}
+
+		this.stopping = true;
+
+		Mono<Void> result;
+		if (this.channelGroup != null) {
+			Sinks.Empty<Void> channnelGroupCloseSink = Sinks.empty();
+			this.channelGroup.close().addListener(future -> channnelGroupCloseSink.tryEmitEmpty());
+			result = channnelGroupCloseSink.asMono();
+			if (this.loopResources != null) {
+				result = result.onErrorResume(ex -> Mono.empty()).then(this.loopResources.disposeLater());
+			}
+			if (this.poolResources != null) {
+				result = result.onErrorResume(ex -> Mono.empty()).then(this.poolResources.disposeLater());
+			}
+			result = result.onErrorResume(ex -> Mono.empty()).then(stopScheduler());
+		}
+		else {
+			result = stopScheduler();
+		}
+
+		return result.toFuture();
+	}
+
+	private Mono<Void> stopScheduler() {
+		return Mono.fromRunnable(() -> {
+			this.scheduler.dispose();
+			for (int i = 0; i < 20; i++) {
+				if (this.scheduler.isDisposed()) {
+					break;
+				}
+				try {
+					Thread.sleep(100);
+				}
+				catch (Throwable ex) {
+					break;
+				}
+			}
+		});
+	}
+
+	@Override
+	public String toString() {
+		return "ReactorNetty2TcpClient[" + this.tcpClient + "]";
+	}
+
+
+	private class ReactorNettyHandler implements BiFunction<NettyInbound, NettyOutbound, Publisher<Void>> {
+
+		private final TcpConnectionHandler<P> connectionHandler;
+
+		ReactorNettyHandler(TcpConnectionHandler<P> handler) {
+			this.connectionHandler = handler;
+		}
+
+		@Override
+		@SuppressWarnings("unchecked")
+		public Publisher<Void> apply(NettyInbound inbound, NettyOutbound outbound) {
+			inbound.withConnection(conn -> {
+				if (logger.isDebugEnabled()) {
+					logger.debug("Connected to " + conn.address());
+				}
+			});
+			Sinks.Empty<Void> completionSink = Sinks.empty();
+			TcpConnection<P> connection = new ReactorNetty2TcpConnection<>(inbound, outbound,  codec, completionSink);
+			scheduler.schedule(() -> this.connectionHandler.afterConnected(connection));
+
+			inbound.withConnection(conn -> conn.addHandlerFirst(new StompMessageDecoder<>(codec)));
+
+			inbound.receiveObject()
+					.cast(Message.class)
+					.publishOn(scheduler, PUBLISH_ON_BUFFER_SIZE)
+					.subscribe(
+							this.connectionHandler::handleMessage,
+							this.connectionHandler::handleFailure,
+							this.connectionHandler::afterConnectionClosed);
+
+			return completionSink.asMono();
+		}
+	}
+
+
+	private static class StompMessageDecoder<P> extends ByteToMessageDecoder {
+
+		private final TcpMessageCodec<P> codec;
+
+		StompMessageDecoder(TcpMessageCodec<P> codec) {
+			this.codec = codec;
+		}
+
+		@Override
+		protected void decode(ChannelHandlerContext ctx, Buffer buffer) throws Exception {
+			ByteBuffer byteBuffer = ByteBuffer.allocate(buffer.readableBytes());
+			buffer.readBytes(byteBuffer);
+			byteBuffer.position(0);
+			List<Message<P>> messages = this.codec.decode(byteBuffer);
+			for (Message<P> message : messages) {
+				ctx.fireChannelRead(message);
+			}
+		}
+
+	}
+
+}

spring-messaging/src/main/java/org/springframework/messaging/tcp/reactor/ReactorNetty2TcpConnection.java

@@ -0,0 +1,84 @@
+/*
+ * Copyright 2002-2022 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.messaging.tcp.reactor;
+
+import java.nio.ByteBuffer;
+import java.util.concurrent.CompletableFuture;
+
+import io.netty5.buffer.api.Buffer;
+import reactor.core.publisher.Mono;
+import reactor.core.publisher.Sinks;
+import reactor.netty5.NettyInbound;
+import reactor.netty5.NettyOutbound;
+
+import org.springframework.messaging.Message;
+import org.springframework.messaging.tcp.TcpConnection;
+
+/**
+ * Reactor Netty based implementation of {@link TcpConnection}.
+ *
+ * <p>This class is based on {@link ReactorNettyTcpConnection}.
+ *
+ * @author Rossen Stoyanchev
+ * @since 6.0
+ * @param <P> the type of payload for outbound messages
+ */
+public class ReactorNetty2TcpConnection<P> implements TcpConnection<P> {
+
+	private final NettyInbound inbound;
+
+	private final NettyOutbound outbound;
+
+	private final TcpMessageCodec<P> codec;
+
+	private final Sinks.Empty<Void> completionSink;
+
+
+	public ReactorNetty2TcpConnection(NettyInbound inbound, NettyOutbound outbound,
+			TcpMessageCodec<P> codec, Sinks.Empty<Void> completionSink) {
+
+		this.inbound = inbound;
+		this.outbound = outbound;
+		this.codec = codec;
+		this.completionSink = completionSink;
+	}
+
+
+	@Override
+	public CompletableFuture<Void> sendAsync(Message<P> message) {
+		ByteBuffer byteBuffer = this.codec.encode(message);
+		Buffer buffer = this.outbound.alloc().copyOf(byteBuffer);
+		return this.outbound.send(Mono.just(buffer)).then().toFuture();
+	}
+
+	@Override
+	public void onReadInactivity(Runnable runnable, long inactivityDuration) {
+		this.inbound.withConnection(conn -> conn.onReadIdle(inactivityDuration, runnable));
+	}
+
+	@Override
+	public void onWriteInactivity(Runnable runnable, long inactivityDuration) {
+		this.inbound.withConnection(conn -> conn.onWriteIdle(inactivityDuration, runnable));
+	}
+
+	@Override
+	public void close() {
+		// Ignore result: concurrent attempts to complete are ok
+		this.completionSink.tryEmitEmpty();
+	}
+
+}

spring-messaging/src/main/java/org/springframework/messaging/tcp/reactor/TcpMessageCodec.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2002-2022 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.messaging.tcp.reactor;
+
+import java.nio.ByteBuffer;
+import java.util.List;
+
+import org.springframework.messaging.Message;
+
+/**
+ * Contract to encode and decode a {@link Message} to and from a {@link ByteBuffer}
+ * allowing a higher-level protocol (e.g. STOMP over TCP) to plug in.
+ *
+ * @author Rossen Stoyanchev
+ * @since 6.0
+ * @param <P> the message payload type
+ */
+public interface TcpMessageCodec<P> {
+
+	/**
+	 * Decode the input {@link ByteBuffer} into one or more {@link Message Messages}.
+	 * @param buffer the input buffer to decode from
+	 * @return 0 or more decoded messages
+	 */
+	List<Message<P>> decode(ByteBuffer buffer);
+
+	/**
+	 * Encode the given {@link Message} to the output {@link ByteBuffer}.
+	 * @param message the message to encode
+	 * @return the encoded buffer
+	 */
+	ByteBuffer encode(Message<P> message);
+
+}

spring-messaging/src/test/java/org/springframework/messaging/simp/stomp/AbstractStompBrokerRelayIntegrationTests.java

@@ -47,6 +47,7 @@ import org.springframework.messaging.simp.SimpMessageType;
 import org.springframework.messaging.simp.broker.BrokerAvailabilityEvent;
 import org.springframework.messaging.support.ExecutorSubscribableChannel;
 import org.springframework.messaging.support.MessageBuilder;
+import org.springframework.messaging.tcp.TcpOperations;
 import org.springframework.util.Assert;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -56,11 +57,10 @@ import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
  * Integration tests for {@link StompBrokerRelayMessageHandler} running against ActiveMQ.
  *
  * @author Rossen Stoyanchev
- * @author Sam Brannen
  */
-public class StompBrokerRelayMessageHandlerIntegrationTests {
+public abstract class AbstractStompBrokerRelayIntegrationTests {
 
-	private static final Log logger = LogFactory.getLog(StompBrokerRelayMessageHandlerIntegrationTests.class);
+	private static final Log logger = LogFactory.getLog(AbstractStompBrokerRelayIntegrationTests.class);
 
 	private StompBrokerRelayMessageHandler relay;
 
@@ -77,7 +77,6 @@ public class StompBrokerRelayMessageHandlerIntegrationTests {
 
 
 	@BeforeEach
-	@SuppressWarnings("deprecation")
 	public void setup(TestInfo testInfo) throws Exception {
 		logger.debug("Setting up before '" + testInfo.getTestMethod().get().getName() + "'");
 
@@ -121,10 +120,15 @@ public class StompBrokerRelayMessageHandlerIntegrationTests {
 		this.relay.setSystemHeartbeatSendInterval(0);
 		this.relay.setPreservePublishOrder(true);
 
+		TcpOperations<byte[]> tcpClient = initTcpClient(this.port);
+		this.relay.setTcpClient(tcpClient);
+
 		this.relay.start();
 		this.eventPublisher.expectBrokerAvailabilityEvent(true);
 	}
 
+	protected abstract TcpOperations<byte[]> initTcpClient(int port);
+
 	@AfterEach
 	public void stop() throws Exception {
 		try {

spring-messaging/src/test/java/org/springframework/messaging/simp/stomp/ReactorNetty2StompBrokerRelayIntegrationTests.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2002-2022 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.messaging.simp.stomp;
+
+import org.springframework.messaging.tcp.TcpOperations;
+import org.springframework.messaging.tcp.reactor.ReactorNetty2TcpClient;
+
+/**
+ * Integration tests for {@link StompBrokerRelayMessageHandler} running against
+ * ActiveMQ with {@link ReactorNetty2TcpClient}.
+ *
+ * @author Rossen Stoyanchev
+ */
+public class ReactorNetty2StompBrokerRelayIntegrationTests extends AbstractStompBrokerRelayIntegrationTests {
+
+	@Override
+	protected TcpOperations<byte[]> initTcpClient(int port) {
+		return new ReactorNetty2TcpClient<>("127.0.0.1", port, new StompTcpMessageCodec());
+	}
+
+}

spring-messaging/src/test/java/org/springframework/messaging/simp/stomp/ReactorNettyStompBrokerRelayIntegrationTests.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2002-2022 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.messaging.simp.stomp;
+
+import org.springframework.messaging.tcp.TcpOperations;
+import org.springframework.messaging.tcp.reactor.ReactorNettyTcpClient;
+
+/**
+ * Integration tests for {@link StompBrokerRelayMessageHandler} running against
+ * ActiveMQ with {@link ReactorNettyTcpClient}.
+ *
+ * @author Rossen Stoyanchev
+ */
+public class ReactorNettyStompBrokerRelayIntegrationTests extends AbstractStompBrokerRelayIntegrationTests {
+
+	@Override
+	protected TcpOperations<byte[]> initTcpClient(int port) {
+		return new ReactorNettyTcpClient<>("127.0.0.1", port, new StompReactorNettyCodec());
+	}
+
+}

spring-messaging/src/test/java/org/springframework/messaging/simp/stomp/ReactorNettyTcpStompClientTests.java

@@ -37,6 +37,7 @@ import org.junit.jupiter.api.TestInfo;
 import org.springframework.lang.Nullable;
 import org.springframework.messaging.converter.StringMessageConverter;
 import org.springframework.messaging.simp.stomp.StompSession.Subscription;
+import org.springframework.messaging.tcp.reactor.ReactorNetty2TcpClient;
 import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
 import org.springframework.util.Assert;
 
@@ -57,6 +58,8 @@ public class ReactorNettyTcpStompClientTests {
 
 	private ReactorNettyTcpStompClient client;
 
+	private ReactorNettyTcpStompClient client2;
+
 
 	@BeforeEach
 	public void setup(TestInfo testInfo) throws Exception {
@@ -75,9 +78,16 @@ public class ReactorNettyTcpStompClientTests {
 		ThreadPoolTaskScheduler taskScheduler = new ThreadPoolTaskScheduler();
 		taskScheduler.afterPropertiesSet();
 
-		this.client = new ReactorNettyTcpStompClient("127.0.0.1", stompConnector.getServer().getSocketAddress().getPort());
+		int port = stompConnector.getServer().getSocketAddress().getPort();
+		String host = "127.0.0.1";
+
+		this.client = new ReactorNettyTcpStompClient(host, port);
 		this.client.setMessageConverter(new StringMessageConverter());
 		this.client.setTaskScheduler(taskScheduler);
+
+		this.client2 = new ReactorNettyTcpStompClient(new ReactorNetty2TcpClient<>(host, port, new StompTcpMessageCodec()));
+		this.client2.setMessageConverter(new StringMessageConverter());
+		this.client2.setTaskScheduler(taskScheduler);
 	}
 
 	private TransportConnector createStompConnector() throws Exception {
@@ -90,6 +100,7 @@ public class ReactorNettyTcpStompClientTests {
 	public void shutdown() throws Exception {
 		try {
 			this.client.shutdown();
+			this.client2.shutdown();
 		}
 		catch (Throwable ex) {
 			logger.error("Failed to shut client", ex);
@@ -103,14 +114,24 @@ public class ReactorNettyTcpStompClientTests {
 		}
 	}
 
+
 	@Test
-	public void publishSubscribe() throws Exception {
+	public void publishSubscribeOnReactorNetty() throws Exception {
+		testPublishSubscribe(this.client);
+	}
+
+	@Test
+	public void publishSubscribeOnReactorNetty2() throws Exception {
+		testPublishSubscribe(this.client2);
+	}
+
+	private void testPublishSubscribe(ReactorNettyTcpStompClient clientToUse) throws Exception {
 		String destination = "/topic/foo";
 		ConsumingHandler consumingHandler1 = new ConsumingHandler(destination);
-		CompletableFuture<StompSession> consumerFuture1 = this.client.connectAsync(consumingHandler1);
+		CompletableFuture<StompSession> consumerFuture1 = clientToUse.connectAsync(consumingHandler1);
 
 		ConsumingHandler consumingHandler2 = new ConsumingHandler(destination);
-		CompletableFuture<StompSession> consumerFuture2 = this.client.connectAsync(consumingHandler2);
+		CompletableFuture<StompSession> consumerFuture2 = clientToUse.connectAsync(consumingHandler2);
 
 		assertThat(consumingHandler1.awaitForSubscriptions(5000)).isTrue();
 		assertThat(consumingHandler2.awaitForSubscriptions(5000)).isTrue();
@@ -118,7 +139,7 @@ public class ReactorNettyTcpStompClientTests {
 		ProducingHandler producingHandler = new ProducingHandler();
 		producingHandler.addToSend(destination, "foo1");
 		producingHandler.addToSend(destination, "foo2");
-		CompletableFuture<StompSession> producerFuture = this.client.connectAsync(producingHandler);
+		CompletableFuture<StompSession> producerFuture = clientToUse.connectAsync(producingHandler);
 
 		assertThat(consumingHandler1.awaitForMessageCount(2, 5000)).isTrue();
 		assertThat(consumingHandler1.getReceived()).containsExactly("foo1", "foo2");