Spring Cleaning in December

- Delete unused imports
- Delete unused code
- Clean up warnings

spring-messaging/src/main/java/org/springframework/messaging/converter/MappingJackson2MessageConverter.java

@@ -38,7 +38,6 @@ import org.springframework.core.MethodParameter;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageHeaders;
 import org.springframework.util.Assert;
-import org.springframework.util.ClassUtils;
 import org.springframework.util.MimeType;
 
 /**
@@ -271,7 +270,7 @@ public class MappingJackson2MessageConverter extends AbstractMessageConverter {
 			return extractViewClass((JsonView) conversionHint, conversionHint);
 		}
 		else if (conversionHint instanceof Class) {
-			return (Class) conversionHint;
+			return (Class<?>) conversionHint;
 		}
 
 		// No JSON view specified...

spring-messaging/src/main/java/org/springframework/messaging/handler/invocation/AsyncHandlerMethodReturnValueHandler.java

@@ -17,7 +17,6 @@
 package org.springframework.messaging.handler.invocation;
 
 import org.springframework.core.MethodParameter;
-import org.springframework.messaging.Message;
 import org.springframework.util.concurrent.ListenableFuture;
 
 /**