Do match message type

SimpMessageTypeMessageCondition was lenient in matching the message
type, essentially matching on any non-null message type with an exact
match given a preference only in comparing mulitple matches.

This commit modifies matching logic to look for an exact match.

Issue: SPR-16109

Author: rstoyanchev

spring-messaging/src/main/java/org/springframework/messaging/simp/SimpMessageTypeMessageCondition.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -74,11 +74,8 @@ public SimpMessageTypeMessageCondition combine(SimpMessageTypeMessageCondition o
 	@Override
 	@Nullable
 	public SimpMessageTypeMessageCondition getMatchingCondition(Message<?> message) {
-		Object actualMessageType = SimpMessageHeaderAccessor.getMessageType(message.getHeaders());
-		if (actualMessageType == null) {
-			return null;
-		}
-		return this;
+		SimpMessageType actual = SimpMessageHeaderAccessor.getMessageType(message.getHeaders());
+		return (actual != null && actual.equals(this.messageType) ? this : null);
 	}
 
 	@Override

spring-messaging/src/test/java/org/springframework/messaging/simp/annotation/support/SimpAnnotationMethodMessageHandlerTests.java

@@ -51,6 +51,7 @@
 import org.springframework.messaging.simp.SimpAttributesContextHolder;
 import org.springframework.messaging.simp.SimpMessageHeaderAccessor;
 import org.springframework.messaging.simp.SimpMessageSendingOperations;
+import org.springframework.messaging.simp.SimpMessageType;
 import org.springframework.messaging.simp.SimpMessagingTemplate;
 import org.springframework.messaging.simp.annotation.SubscribeMapping;
 import org.springframework.messaging.support.MessageBuilder;
@@ -159,7 +160,7 @@ public void messageMappingDestinationVariableResolution() {
 
 	@Test
 	public void subscribeEventDestinationVariableResolution() {
-		Message<?> message = createMessage("/pre/sub/bar/value");
+		Message<?> message = createMessage(SimpMessageType.SUBSCRIBE, "/pre/sub/bar/value", null);
 		this.messageHandler.registerHandler(this.testController);
 		this.messageHandler.handleMessage(message);
 
@@ -328,7 +329,11 @@ private Message<?> createMessage(String destination) {
 	}
 
 	private Message<?> createMessage(String destination, Map<String, Object> headers) {
-		SimpMessageHeaderAccessor accessor = SimpMessageHeaderAccessor.create();
+		return createMessage(SimpMessageType.MESSAGE, destination, headers);
+	}
+
+	private Message<?> createMessage(SimpMessageType messageType, String destination, Map<String, Object> headers) {
+		SimpMessageHeaderAccessor accessor = SimpMessageHeaderAccessor.create(messageType);
 		accessor.setSessionId("session1");
 		accessor.setSessionAttributes(new HashMap<>());
 		accessor.setDestination(destination);