Fix support for @RequestBody on interface methods

Previously, @RequestBody annotations declared in interfaces were
ignored when resolving the `required` flag for request body
matching. This caused mappings with `required = false` on
interface methods to fail if no body was provided.

This change uses AnnotatedMethod to retrieve parameter
annotations from both the implementation and its interfaces,
ensuring consistent behavior.

Closes #35085

Signed-off-by: Renato Mameli <[email protected]>

Author: Renato Mameli

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

@@ -19,7 +19,6 @@
 import java.lang.annotation.Annotation;
 import java.lang.reflect.AnnotatedElement;
 import java.lang.reflect.Method;
-import java.lang.reflect.Parameter;
 import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -31,7 +30,9 @@
 import org.jspecify.annotations.Nullable;
 
 import org.springframework.context.EmbeddedValueResolverAware;
+import org.springframework.core.MethodParameter;
 import org.springframework.core.annotation.AnnotatedElementUtils;
+import org.springframework.core.annotation.AnnotatedMethod;
 import org.springframework.core.annotation.MergedAnnotation;
 import org.springframework.core.annotation.MergedAnnotationPredicates;
 import org.springframework.core.annotation.MergedAnnotations;
@@ -410,13 +411,17 @@ protected void registerHandlerMethod(Object handler, Method method, RequestMappi
 
 	private void updateConsumesCondition(RequestMappingInfo info, Method method) {
 		ConsumesRequestCondition condition = info.getConsumesCondition();
-		if (!condition.isEmpty()) {
-			for (Parameter parameter : method.getParameters()) {
-				MergedAnnotation<RequestBody> annot = MergedAnnotations.from(parameter).get(RequestBody.class);
-				if (annot.isPresent()) {
-					condition.setBodyRequired(annot.getBoolean("required"));
-					break;
-				}
+		if (condition.isEmpty()) {
+			return;
+		}
+
+		AnnotatedMethod annotatedMethod = new AnnotatedMethod(method);
+
+		for (MethodParameter parameter : annotatedMethod.getMethodParameters()) {
+			RequestBody requestBodyAnnotation = parameter.getParameterAnnotation(RequestBody.class);
+			if (requestBodyAnnotation != null) {
+				condition.setBodyRequired(requestBodyAnnotation.required());
+				break;
 			}
 		}
 	}

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

@@ -386,6 +386,52 @@ void httpExchangeWithCustomHeaders() throws Exception {
 				.containsExactly("h1=hv1", "!h2");
 	}
 
+	@Test
+	void httpExchangeAnnotationOfRequestBodyIsTakenFromInterface() throws Exception {
+		RequestMappingHandlerMapping mapping = createMapping();
+
+		Class<?> controllerClass = InterfaceControllerImpl.class;
+		Method method = controllerClass.getDeclaredMethod("post", Foo.class);
+
+		RequestMappingInfo info = mapping.getMappingForMethod(method, controllerClass);
+		assertThat(info).isNotNull();
+
+		mapping.registerHandlerMethod(new InterfaceControllerImpl(), method, info);
+
+		assertThat(info.getConsumesCondition()).isNotNull();
+		assertThat(info.getConsumesCondition().isBodyRequired()).isFalse();
+		assertThat(info.getConsumesCondition().getConsumableMediaTypes()).containsOnly(MediaType.APPLICATION_JSON);
+
+		MockHttpServletRequest request = new MockHttpServletRequest("POST", "/controller/postMapping");
+		initRequestPath(mapping, request);
+
+		RequestMappingInfo matchingInfo = info.getMatchingCondition(request);
+		assertThat(matchingInfo).isNotNull();
+	}
+
+	@Test
+	void httpExchangeAnnotationOfRequestBodyOverwrittenByImpl() throws Exception {
+		RequestMappingHandlerMapping mapping = createMapping();
+
+		Class<?> controllerClass = InterfaceControllerImplOverridesRequestBody.class;
+		Method method = controllerClass.getDeclaredMethod("post", Foo.class);
+
+		RequestMappingInfo info = mapping.getMappingForMethod(method, controllerClass);
+		assertThat(info).isNotNull();
+
+		mapping.registerHandlerMethod(new InterfaceControllerImpl(), method, info);
+
+		assertThat(info.getConsumesCondition()).isNotNull();
+		assertThat(info.getConsumesCondition().isBodyRequired()).isTrue();
+		assertThat(info.getConsumesCondition().getConsumableMediaTypes()).containsOnly(MediaType.APPLICATION_JSON);
+
+		MockHttpServletRequest request = new MockHttpServletRequest("POST", "/controller/postMapping");
+		initRequestPath(mapping, request);
+
+		RequestMappingInfo matchingInfo = info.getMatchingCondition(request);
+		assertThat(matchingInfo).isNull();
+	}
+
 	private static RequestMappingHandlerMapping createMapping() {
 		RequestMappingHandlerMapping mapping = new RequestMappingHandlerMapping();
 		mapping.setApplicationContext(new StaticWebApplicationContext());
@@ -571,6 +617,22 @@ static class MethodLevelOverriddenHttpExchangeAnnotationsController implements S
 		public void post() {}
 	}
 
+	@RestController
+	@RequestMapping(value = "/controller", consumes = { "application/json" })
+	interface InterfaceController {
+		@PostMapping("/postMapping")
+		void post(@RequestBody(required = false) Foo foo);
+	}
+
+	static class InterfaceControllerImpl implements InterfaceController {
+		@Override
+		public void post(Foo foo) {}
+	}
+
+	static class InterfaceControllerImplOverridesRequestBody implements InterfaceController {
+		@Override
+		public void post(@RequestBody(required = true) Foo foo) {}
+	}
 
 	@HttpExchange
 	@Target(ElementType.TYPE)