Enhancement in HandlerMethodValidationException

Add dedicated method to Visitor for constraints directly on a
RequestBody method parameter (rather than nested).

Closes gh-34549

Author: rstoyanchev

spring-web/src/main/java/org/springframework/web/method/annotation/HandlerMethodValidationException.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -146,7 +146,12 @@ public void visitResults(Visitor visitor) {
 			}
 			RequestBody requestBody = param.getParameterAnnotation(RequestBody.class);
 			if (requestBody != null) {
-				visitor.requestBody(requestBody, asErrors(result));
+				if (result instanceof ParameterErrors errors) {
+					visitor.requestBody(requestBody, errors);
+				}
+				else {
+					visitor.requestBodyValidationResult(requestBody, result);
+				}
 				continue;
 			}
 			RequestHeader requestHeader = param.getParameterAnnotation(RequestHeader.class);
@@ -216,6 +221,20 @@ public interface Visitor {
 		 */
 		void requestBody(RequestBody requestBody, ParameterErrors errors);
 
+		/**
+		 * An additional {@code @RequestBody} callback for validation failures
+		 * for constraints on the method parameter. For example:
+		 * <pre>
+		 * &#064;RequestBody List<&#064;NotEmpty String> ids
+		 * </pre>
+		 * Handle results for {@code @RequestBody} method parameters.
+		 * @param requestBody the annotation declared on the parameter
+		 * @param result the validation result
+		 * @since 7.0
+		 */
+		default void requestBodyValidationResult(RequestBody requestBody, ParameterValidationResult result) {
+		}
+
 		/**
 		 * Handle results for {@code @RequestHeader} method parameters.
 		 * @param requestHeader the annotation declared on the parameter

spring-web/src/test/java/org/springframework/web/method/support/HandlerMethodValidationExceptionTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -25,6 +25,7 @@
 import java.util.function.Predicate;
 
 import jakarta.validation.Valid;
+import jakarta.validation.constraints.NotEmpty;
 import jakarta.validation.constraints.Size;
 import org.junit.jupiter.api.Test;
 
@@ -67,7 +68,7 @@ class HandlerMethodValidationExceptionTests {
 
 
 	private final HandlerMethod handlerMethod = handlerMethod(new ValidController(),
-			controller -> controller.handle(person, person, person, person, "", "", "", "", "", ""));
+			controller -> controller.handle(person, person, person, List.of(), person, "", "", "", "", "", ""));
 
 	private final TestVisitor visitor = new TestVisitor();
 
@@ -84,7 +85,7 @@ void traverse() {
 
 		assertThat(this.visitor.getOutput()).isEqualTo("""
 				@ModelAttribute: modelAttribute1, @ModelAttribute: modelAttribute2, \
-				@RequestBody: requestBody, @RequestPart: requestPart, \
+				@RequestBody: requestBody, @RequestBody: requestBodyList, @RequestPart: requestPart, \
 				@RequestParam: requestParam1, @RequestParam: requestParam2, \
 				@RequestHeader: header, @PathVariable: pathVariable, \
 				@CookieValue: cookie, @MatrixVariable: matrixVariable""");
@@ -100,7 +101,7 @@ void traverseRemaining() {
 
 		assertThat(this.visitor.getOutput()).isEqualTo("""
 				Other: modelAttribute1, @ModelAttribute: modelAttribute2, \
-				@RequestBody: requestBody, @RequestPart: requestPart, \
+				@RequestBody: requestBody, @RequestBody: requestBodyList, @RequestPart: requestPart, \
 				Other: requestParam1, @RequestParam: requestParam2, \
 				@RequestHeader: header, @PathVariable: pathVariable, \
 				@CookieValue: cookie, @MatrixVariable: matrixVariable""");
@@ -155,6 +156,7 @@ void handle(
 				@Valid Person modelAttribute1,
 				@Valid @ModelAttribute Person modelAttribute2,
 				@Valid @RequestBody Person requestBody,
+				@RequestBody List<@NotEmpty String> requestBodyList,
 				@Valid @RequestPart Person requestPart,
 				@Size(min = 5) String requestParam1,
 				@Size(min = 5) @RequestParam String requestParam2,
@@ -222,6 +224,11 @@ public void requestBody(RequestBody requestBody, ParameterErrors errors) {
 			handle(requestBody, errors);
 		}
 
+		@Override
+		public void requestBodyValidationResult(RequestBody requestBody, ParameterValidationResult result) {
+			handle(requestBody, result);
+		}
+
 		@Override
 		public void requestHeader(RequestHeader requestHeader, ParameterValidationResult result) {
 			handle(requestHeader, result);