MultipartFile custom annotations validation

Question

I've a file upload validation that raises a BindException instead of a MethodArgumentNotValidException and I don't understand why.

  org.springframework.validation.BindException: org.springframework.validation.BeanPropertyBindingResult: 1 errors
Field error in object 'patientProfileImageDTO' on field 'profileImage': rejected value [org.springframework.web.multipart.commons.CommonsMultipartFile@2840a305]; codes [CheckImageFormat.patientProfileImageDTO.profileImage,CheckImageFormat.profileImage,CheckImageFormat.org.springframework.web.multipart.MultipartFile,CheckImageFormat]; arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [patientProfileImageDTO.profileImage,profileImage]; arguments []; default message [profileImage]]; default message [Invalid image format (allowed: png, jpg, jpeg)]

My Controller is:

@PostMapping("/patient/image")
public ResponseEntity<?> updateProfileImage(@Validated PatientProfileImageDTO patientProfileImageDTO)

and this is the PatientProfileImageDTO

public class PatientProfileImageDTO {
        
    @CheckImageFormat   
    @CheckImageSize
    private MultipartFile profileImage;
    
    public MultipartFile getProfileImage() {
        return profileImage;
    }
    
    public void setProfileImage(MultipartFile profileImage) {
        this.profileImage = profileImage;
    }

}

the CheckFormatImage and CheckImageSize validators are correctly invoked.

I need to catch these errors in my:

@ControllerAdvice
public class ApiExceptionHandler {
        
        ExceptionHandler(MethodArgumentNotValidException.class)
        protected ResponseEntity<Object> handleMethodArgumentNotValid(MethodArgumentNotValidException ex, WebRequest request) {
        
        ...
        }
    }

I've other custom validation annotations in another part of my code and they work as intended.

I mean:

@OldPasswordMatch(message = "old password mismatch")
private String oldPassword;

This custom validation triggers a MethodArgumentNotValidException that what I want.

What's wrong with my code?

Thanks.

Answer 1

There is also a BindException thrown by Spring MVC if an invalid object was created from the request parameters. MethodArgumentNotValidException is already a subclass of BindException .

These are actually intentionally different exceptions. @ModelAttribute, which is assumed by default if no other annotation is present, goes through data binding and validation, and raises BindException to indicate a failure with binding request properties or validating the resulting values. @RequestBody, on the other hand converts the body of the request via other converter, validates it and raises various conversion related exceptions or a MethodArgumentNotValidException if validation fails. In most cases a MethodArgumentNotValidException can be handled generically (eg via @ExceptionHandler method) while BindException is very often handled individually in each controller method.

You can process these errors separately or you can catch only the super class BindException .

@ExceptionHandler(BindException.class)
protected ResponseEntity<Object> handleBindException(BindException ex) {
    // ..
}