ControllerAdviceBean accepts bean types without @ControllerAdvice annotation (as in 3.2)

Issue: SPR-13759

spring-web/src/main/java/org/springframework/web/method/ControllerAdviceBean.java

@@ -19,6 +19,7 @@ package org.springframework.web.method;
 import java.lang.annotation.Annotation;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Set;
@@ -102,13 +103,16 @@ public class ControllerAdviceBean implements Ordered {
 		}
 
 		ControllerAdvice annotation = AnnotationUtils.findAnnotation(beanType, ControllerAdvice.class);
-		if (annotation == null) {
-			throw new IllegalArgumentException(
-					"Bean type [" + beanType.getName() + "] is not annotated as @ControllerAdvice");
+		if (annotation != null) {
+			this.basePackages = initBasePackages(annotation);
+			this.assignableTypes = Arrays.asList(annotation.assignableTypes());
+			this.annotations = Arrays.asList(annotation.annotations());
+		}
+		else {
+			this.basePackages = Collections.emptySet();
+			this.assignableTypes = Collections.emptyList();
+			this.annotations = Collections.emptyList();
 		}
-		this.basePackages = initBasePackages(annotation);
-		this.assignableTypes = Arrays.asList(annotation.assignableTypes());
-		this.annotations = Arrays.asList(annotation.annotations());
 	}