Validation in Spring Data throws ConstraintViolationException

I'm trying to implement a validation for my service based on Spring Data. The documentation online says, thet i would only need the annotations of javax.validation and everything should work fine.
By fine I mean that if the validation failes it throws a MethodArgumentNotValidException that can be catched and handled (which should spring do by magic).

However I'm not able to achieve this on my project, whenever I implement the validation a ConstraintViolationException inside a TransactionSystemException is thrown instead.

Here is a minimal example:

Entity:

@Entity
@Data
@NoArgsConstructor(access = AccessLevel.PROTECTED)
public class Foo {
  @Id
  UUID id = UUID.randomUUID();

  @NotBlank
  String name;
}

Repository:

public interface FooRepository extends PagingAndSortingRepository<Foo, UUID> {

}

Controller:

@RepositoryRestController
public class FooController {

  @Autowired
  FooRepository fooRepository;

  @PostMapping(value = "/foos", consumes = {MediaType.APPLICATION_JSON_VALUE, MediaTypes.HAL_JSON_VALUE})
  public @ResponseBody ResponseEntity<?> postFoo(HttpServletRequest request, @Valid @RequestBody Foo foo,
      PersistentEntityResourceAssembler resourceAssembler) {
    Foo savedFoo = fooRepository.save(foo);

    return new ResponseEntity<>(resourceAssembler.toFullResource(savedFoo), HttpStatus.CREATED);
  }
}

And the test code with which I run the code:

@SpringBootTest
@AutoConfigureMockMvc(addFilters = false)
@AutoConfigureDataJpa
class FooTest {
  @Autowired
  MockMvc mockMvc;

  @Test
  void testPost() throws Exception {
    Foo foo = new Foo();
    assertNull(foo.getName());

    mockMvc.perform(
        post("/foos")
            .contentType(MediaType.APPLICATION_JSON)
            .content(new ObjectMapper().writeValueAsString(foo)))
        .andDo(print())
        .andExpect(status().isBadRequest());
  }
}

The Exception thrown is the following:

Caused by: javax.validation.ConstraintViolationException: Validation failed for classes [Foo] during persist time for groups [javax.validation.groups.Default, ]
List of constraint violations:[
	ConstraintViolationImpl{interpolatedMessage='darf nicht leer sein', propertyPath=name, rootBeanClass=class Foo, messageTemplate='{javax.validation.constraints.NotBlank.message}'}
]
	at org.hibernate.cfg.beanvalidation.BeanValidationEventListener.validate(BeanValidationEventListener.java:140)
	at org.hibernate.cfg.beanvalidation.BeanValidationEventListener.onPreInsert(BeanValidationEventListener.java:80)
	at org.hibernate.action.internal.EntityInsertAction.preInsert(EntityInsertAction.java:227)
	at org.hibernate.action.internal.EntityInsertAction.execute(EntityInsertAction.java:100)
	at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:604)
	at org.hibernate.engine.spi.ActionQueue.lambda$executeActions$1(ActionQueue.java:478)

ConstraintViolationException is not related to validation. It is because you are saving same foo object everytime you calling test method testPost(). Everytime you are saving foo use different id. Id is the primary key and if you save more than one object with same id or primary key you will get ConstraintViolationException.

I have now found a solution, but I do not really understand it yet. I will investigate this further and share my results here, if anyone can explain it to me, feel free to comment.

I solved it by annotating my Controller with @RestController instead of @RepositoryRestController.

https://jira.spring.io/browse/DATAREST-593

This soultion works for me: https://stackoverflow.com/a/44304198/4567795