Add default web handling of method validation errors

Closes gh-30644

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/MethodValidationTests.java

@@ -43,7 +43,6 @@ import org.springframework.validation.FieldError;
 import org.springframework.validation.Validator;
 import org.springframework.validation.annotation.Validated;
 import org.springframework.validation.beanvalidation.LocalValidatorFactoryBean;
-import org.springframework.validation.beanvalidation.MethodValidationException;
 import org.springframework.validation.beanvalidation.ParameterValidationResult;
 import org.springframework.validation.beanvalidation.SpringValidatorAdapter;
 import org.springframework.web.bind.WebDataBinder;
@@ -55,6 +54,7 @@ import org.springframework.web.bind.support.ConfigurableWebBindingInitializer;
 import org.springframework.web.bind.support.WebExchangeBindException;
 import org.springframework.web.context.support.GenericWebApplicationContext;
 import org.springframework.web.method.HandlerMethod;
+import org.springframework.web.method.annotation.HandlerMethodValidationException;
 import org.springframework.web.reactive.HandlerResult;
 import org.springframework.web.server.ServerWebExchange;
 import org.springframework.web.testfixture.http.server.reactive.MockServerHttpRequest;
@@ -202,7 +202,7 @@ public class MethodValidationTests {
 
 		StepVerifier.create(this.handlerAdapter.handle(exchange, hm))
 				.consumeErrorWith(throwable -> {
-					MethodValidationException ex = (MethodValidationException) throwable;
+					HandlerMethodValidationException ex = (HandlerMethodValidationException) throwable;
 
 					assertThat(this.jakartaValidator.getValidationCount()).isEqualTo(1);
 					assertThat(this.jakartaValidator.getMethodValidationCount()).isEqualTo(1);

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/ResponseEntityExceptionHandlerTests.java

@@ -37,9 +37,12 @@ import org.springframework.http.ProblemDetail;
 import org.springframework.http.ResponseEntity;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.validation.BeanPropertyBindingResult;
+import org.springframework.validation.beanvalidation.MethodValidationException;
+import org.springframework.validation.beanvalidation.MethodValidationResult;
 import org.springframework.web.ErrorResponse;
 import org.springframework.web.ErrorResponseException;
 import org.springframework.web.bind.support.WebExchangeBindException;
+import org.springframework.web.method.annotation.HandlerMethodValidationException;
 import org.springframework.web.server.MethodNotAllowedException;
 import org.springframework.web.server.MissingRequestValueException;
 import org.springframework.web.server.NotAcceptableStatusException;
@@ -53,6 +56,7 @@ import org.springframework.web.testfixture.http.server.reactive.MockServerHttpRe
 import org.springframework.web.testfixture.server.MockServerWebExchange;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.BDDMockito.mock;
 
 /**
  * Unit tests for {@link ResponseEntityExceptionHandler}.
@@ -105,6 +109,21 @@ public class ResponseEntityExceptionHandlerTests {
 		testException(new WebExchangeBindException(null, new BeanPropertyBindingResult(new Object(), "foo")));
 	}
 
+	@Test
+	public void handlerMethodValidationException() {
+		testException(new HandlerMethodValidationException(mock(MethodValidationResult.class)));
+	}
+
+	@Test
+	public void methodValidationException() {
+		MethodValidationException ex = new MethodValidationException(mock(MethodValidationResult.class));
+		ResponseEntity<?> entity = this.exceptionHandler.handleException(ex, this.exchange).block();
+
+		assertThat(entity).isNotNull();
+		assertThat(entity.getStatusCode()).isEqualTo(HttpStatus.INTERNAL_SERVER_ERROR);
+		assertThat(entity.getBody()).isInstanceOf(ProblemDetail.class);
+	}
+
 	@Test
 	void handleServerWebInputException() {
 		testException(new ServerWebInputException(""));