Built-in method validation does not work with Boot auto-configuration

[sephiroth-j]

There are two issues with the new feature of validating method parameters.

1. Validation happens only if @Validated is used on the class level. If it is used on method level, nothing happens at all. The documentation suggest to remove class level annotation and use a method level annotation instead.
   

   spring-framework/framework-docs/modules/ROOT/pages/web/webflux/controller/ann-validation.adoc

   Lines 33 to 37 in 1e30997

   	NOTE: If a controller has a class level `@Validated`, then
   	xref:core/validation/beanvalidation.adoc#validation-beanvalidation-spring-method[method validation is applied]
   	through an AOP proxy. In order to take advantage of the Spring MVC built-in support for
   	method validation added in Spring Framework 6.1, you need to remove the class level
   	`@Validated` annotation from the controller.

2023-08-21T09:39:56.099+02:00 DEBUG 11436 --- [           main] o.s.w.r.f.client.ExchangeFunctions       : [2f04993d] HTTP GET /method/-1
2023-08-21T09:39:56.111+02:00 DEBUG 11436 --- [     parallel-1] o.s.t.w.r.server.HttpHandlerConnector    : Writing client request for  GET "/method/-1"
2023-08-21T09:39:56.118+02:00 DEBUG 11436 --- [     parallel-1] o.s.t.w.r.server.HttpHandlerConnector    : Invoking HttpHandler for  GET "/method/-1"
2023-08-21T09:39:56.126+02:00 DEBUG 11436 --- [     parallel-1] o.s.w.s.adapter.HttpWebHandlerAdapter    : [5d04b1ce] HTTP GET "/method/-1"
2023-08-21T09:39:56.143+02:00 DEBUG 11436 --- [     parallel-1] s.w.r.r.m.a.RequestMappingHandlerMapping : [5d04b1ce] Mapped to com.example.demo.MethodLevelController#getEntity(Long)
2023-08-21T09:39:56.164+02:00 DEBUG 11436 --- [     parallel-1] o.s.w.s.adapter.HttpWebHandlerAdapter    : [5d04b1ce] Completed 200 OK
2023-08-21T09:39:56.170+02:00 DEBUG 11436 --- [     parallel-1] o.s.t.w.r.server.HttpHandlerConnector    : Creating client response for  GET "/method/-1"
2023-08-21T09:39:56.176+02:00 DEBUG 11436 --- [     parallel-1] o.s.w.r.f.client.ExchangeFunctions       : [2f04993d] [7eae50ac] Response 200 OK

2. On class level: Instead of an expected bad request response, an internal server error is thrown.

2023-08-21T09:36:05.610+02:00 DEBUG 11860 --- [           main] o.s.w.r.f.client.ExchangeFunctions       : [200d1a3d] HTTP GET /class/-1
2023-08-21T09:36:05.610+02:00 DEBUG 11860 --- [     parallel-2] o.s.t.w.r.server.HttpHandlerConnector    : Writing client request for  GET "/class/-1"
2023-08-21T09:36:05.610+02:00 DEBUG 11860 --- [     parallel-2] o.s.t.w.r.server.HttpHandlerConnector    : Invoking HttpHandler for  GET "/class/-1"
2023-08-21T09:36:05.610+02:00 DEBUG 11860 --- [     parallel-2] o.s.w.s.adapter.HttpWebHandlerAdapter    : [70770775] HTTP GET "/class/-1"
2023-08-21T09:36:05.611+02:00 DEBUG 11860 --- [     parallel-2] s.w.r.r.m.a.RequestMappingHandlerMapping : [70770775] Mapped to com.example.demo.ClassLevelController#getEntity(Long)
2023-08-21T09:36:05.618+02:00 DEBUG 11860 --- [     parallel-2] o.h.v.r.PlatformResourceBundleLocator    : ValidationMessages not found.
2023-08-21T09:36:05.619+02:00 DEBUG 11860 --- [     parallel-2] o.h.v.r.PlatformResourceBundleLocator    : ContributorValidationMessages not found.
2023-08-21T09:36:05.621+02:00 DEBUG 11860 --- [     parallel-2] o.h.v.r.PlatformResourceBundleLocator    : org.hibernate.validator.ValidationMessages found.
2023-08-21T09:36:05.642+02:00 DEBUG 11860 --- [     parallel-2] a.w.r.e.AbstractErrorWebExceptionHandler : [70770775] Resolved [ConstraintViolationException: getEntity.id: muss größer als 0 sein] for HTTP GET /class/-1
2023-08-21T09:36:05.643+02:00 ERROR 11860 --- [     parallel-2] a.w.r.e.AbstractErrorWebExceptionHandler : [70770775]  500 Server Error for HTTP GET "/class/-1"

jakarta.validation.ConstraintViolationException: getEntity.id: muss größer als 0 sein
	at org.springframework.validation.beanvalidation.MethodValidationInterceptor.invoke(MethodValidationInterceptor.java:146) ~[spring-context-6.1.0-M4.jar:6.1.0-M4]
	Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException: 
Error has been observed at the following site(s):
	*__checkpoint ? HTTP GET "/class/-1" [ExceptionHandlingWebHandler]
Original Stack Trace:
		at org.springframework.validation.beanvalidation.MethodValidationInterceptor.invoke(MethodValidationInterceptor.java:146) ~[spring-context-6.1.0-M4.jar:6.1.0-M4]
		at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) ~[spring-aop-6.1.0-M4.jar:6.1.0-M4]
		at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:751) ~[spring-aop-6.1.0-M4.jar:6.1.0-M4]
		at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:703) ~[spring-aop-6.1.0-M4.jar:6.1.0-M4]
		at com.example.demo.ClassLevelController$$SpringCGLIB$$0.getEntity(<generated>) ~[classes/:na]
		at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
		at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[na:na]
		at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
		at java.base/java.lang.reflect.Method.invoke(Method.java:568) ~[na:na]
		at org.springframework.web.reactive.result.method.InvocableHandlerMethod.lambda$invoke$0(InvocableHandlerMethod.java:178) ~[spring-webflux-6.1.0-M4.jar:6.1.0-M4]

Tested with Spring Boot 3.2.0-M1 and Spring Framework 6.1.0-M3 and 6.1.0-M4. Sample project is attached.

spring-boot-reactive-demo.zip

[sdeleuze]

@rstoyanchev See #31045 where I worked on WebFlux type conversion refinements to get a bad request response instead of an internal server error.

[rstoyanchev]

Thanks for the sample.

For built-in method validation to work, there needs be a globally configured jakarta.validation.Validator. However, it looks like WebFluxAutoConfigurationSupport overrides the webFluxValidator bean method, and adds a ValidatorAdapter wrapper which intentionally hides the jakarta.validation.Validator. As a result, HandlerMethodValidator#from does not see the validator as a Jakarta Validator and method validation is not applied. The same is done in WebMvcAutoConfigurationSupport so the issue applies to Spring MVC too.

ValidatorAdapter has a getTarget method, but the Spring Framework can't depend on a Spring Boot class. We need to figure something out.

By the way, the built-in method validation does not need a method-level @Validated. In other words the following is sufficient (once this issue is resolved) because there is a constraint annotation:

@RestController
@RequestMapping(produces = MediaType.APPLICATION_JSON_VALUE, path = "/method")
public class MethodLevelController {

	@GetMapping(path = "/{id}")
	public Mono<Void> getEntity(@PathVariable @Positive Long id) {
		return Mono.empty();
	}
}