Custom constraint validation annotation for MultipartFile

I'm trying to make an annotation to validate a list of MultipartFile on the controller parameters, but it doesn't seem to make any effect. No exception is thrown, not error at all.
I looked at some similar questions but it didn't work.

• Interface:

  @Target(ElementType.PARAMETER)
  @Retention(RetentionPolicy.RUNTIME)
  @Constraint(validatedBy = {ImageValidator.class})
  public @interface ValidImage {
    String message() default "Invalid image file";
  
    Class<?>[] groups() default {};
  
    Class<? extends Payload>[] payload() default {};
  }
  

• Class:

  public class ImageValidator implements ConstraintValidator<ValidImage, List<MultipartFile>> {
  
    @Override
    public boolean isValid(
  	  List<MultipartFile> listMultipartFile, ConstraintValidatorContext context) {
  
  	for (var multipartFile : listMultipartFile) {
  	  var contentType = multipartFile.getContentType();
  	  if (!isSupportedContentType(contentType)) {
  		context.disableDefaultConstraintViolation();
  		context
  			.buildConstraintViolationWithTemplate("Only JPG and PNG images are allowed.")
  			.addConstraintViolation();
  		return false;
  	  }
  	}
  
  	return true;
    }
  
    private boolean isSupportedContentType(String contentType) {
  	var supportedContents = List.of("image/jpg", "image/jpeg", "image/png");
  	return supportedContents.contains(contentType);
    }
  }
  

• Usage:

  @PostMapping(value = "images")
    public ResponseEntity<List<ExerciseImageDTO>> uploadImages(
  	  @RequestParam(value = "images", required = true) @ValidImage List<@Valid MultipartFile> images) {
  
  	.......
  	return ResponseEntity.ok(createdImages);
    }
  

you need @Validated on your controller class like this

    @Controller
    @Validated
    public class SampleController {

      @PostMapping(value = "images")
      public ResponseEntity<List<ExerciseImageDTO>> uploadImages(
      @RequestParam(value = "images", required = true) @ValidImage List<@Valid MultipartFile> images) {
        .......
        return ResponseEntity.ok(createdImages);
      }

    }