Use custom config read in ReactorTcpClient

Use a custom ConfigReader to enforce the use of SynchronousDispatcher
and no other dispatchers otherwise created by default. Avoids the
creation thread pools never to be used.

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

@@ -16,6 +16,7 @@
 
 package org.springframework.messaging.simp.stomp;
 
+import java.io.IOException;
 import java.util.Collection;
 import java.util.Map;
 import java.util.concurrent.Callable;

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

@@ -18,6 +18,9 @@ package org.springframework.messaging.tcp.reactor;
 
 import java.lang.reflect.Modifier;
 import java.net.InetSocketAddress;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.Properties;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -34,6 +37,9 @@ import reactor.core.composable.Deferred;
 import reactor.core.composable.Promise;
 import reactor.core.composable.Stream;
 import reactor.core.composable.spec.Promises;
+import reactor.core.configuration.ConfigurationReader;
+import reactor.core.configuration.DispatcherConfiguration;
+import reactor.core.configuration.ReactorConfiguration;
 import reactor.function.Consumer;
 import reactor.function.support.SingleUseConsumer;
 import reactor.io.Buffer;
@@ -81,13 +87,12 @@ public class ReactorTcpClient<P> implements TcpOperations<P> {
 	public ReactorTcpClient(String host, int port, Codec<Buffer, Message<P>, Message<P>> codec) {
 
 		// Revisit in 1.1: is Environment still required w/ sync dispatcher?
-		this.environment = new Environment();
+		this.environment = new Environment(new SynchronousDispatcherConfigReader());
 
 		this.tcpClient = new TcpClientSpec<Message<P>, Message<P>>(REACTOR_TCP_CLIENT_TYPE)
 				.env(this.environment)
 				.codec(codec)
 				.connect(host, port)
-				.synchronousDispatcher()
 				.get();
 
 		checkReactorVersion();
@@ -228,4 +233,20 @@ public class ReactorTcpClient<P> implements TcpOperations<P> {
 		}
 	}
 
+
+	/**
+	 * A ConfigurationReader that enforces the use of a SynchronousDispatcher.
+	 *
+	 * <p>The {@link reactor.core.configuration.PropertiesConfigurationReader} used by
+	 * default automatically creates other dispatchers with thread pools that are
+	 * not needed.
+	 */
+	private static class SynchronousDispatcherConfigReader implements ConfigurationReader {
+
+		@Override
+		public ReactorConfiguration read() {
+			return new ReactorConfiguration(Arrays.<DispatcherConfiguration>asList(), "sync", new Properties());
+		}
+	}
+
 }