MessageChannel declares send(Message) as default method

Issue: SPR-14854

spring-messaging/src/main/java/org/springframework/messaging/MessageChannel.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -22,12 +22,13 @@ package org.springframework.messaging;
  * @author Mark Fisher
  * @since 4.0
  */
+@FunctionalInterface
 public interface MessageChannel {
 
 	/**
 	 * Constant for sending a message without a prescribed timeout.
 	 */
-	public static final long INDEFINITE_TIMEOUT = -1;
+	long INDEFINITE_TIMEOUT = -1;
 
 
 	/**
@@ -40,7 +41,9 @@ public interface MessageChannel {
 	 * @param message the message to send
 	 * @return whether or not the message was sent
 	 */
-	boolean send(Message<?> message);
+	default boolean send(Message<?> message) {
+		return send(message, INDEFINITE_TIMEOUT);
+	}
 
 	/**
 	 * Send a message, blocking until either the message is accepted or the