Discover controllers based on type @RequestMapping

This was supported in DefaultAnnotationHandlerMapping but not in the
RequestMappingHandlerMapping. The specific scenario where this matters
is a controller decorated with a JDK proxy. In this scenario the
HandlerMapping looks at interfaces only to decide if the bean is a
controller. The @Controller annotation is better left (and required)
on the class.

Issue: SPR-9374

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/RequestMappingHandlerMapping.java

@@ -83,7 +83,8 @@ public class RequestMappingHandlerMapping extends RequestMappingInfoHandlerMappi
 	 */
 	@Override
 	protected boolean isHandler(Class<?> beanType) {
-		return AnnotationUtils.findAnnotation(beanType, Controller.class) != null;
+		return ((AnnotationUtils.findAnnotation(beanType, Controller.class) != null) ||
+				(AnnotationUtils.findAnnotation(beanType, RequestMapping.class) != null));
 	}
 
 	/**

spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/HandlerMethodAnnotationDetectionTests.java

@@ -208,8 +208,9 @@ public class HandlerMethodAnnotationDetectionTests {
 		}
 	}
 
+	// SPR-9374
 
-	@Controller
+	@RequestMapping
 	static interface MappingInterface {
 
 		@InitBinder
@@ -300,8 +301,7 @@ public class HandlerMethodAnnotationDetectionTests {
 		}
 	}
 
-	
+	@RequestMapping
-	@Controller
 	static interface MappingParameterizedInterface<A, B, C> {
 
 		@InitBinder