Add binding for validation

Peter Penzov :

I want to create Spring endpoint for validating Java Object. I tried to implement this example:

https://www.baeldung.com/validation-angularjs-spring-mvc

I tried this:

public class WpfPaymentsDTO {

    @NotNull
    @Size(min = 4, max = 15)
    private String card_holder;

    private String card_number;
    ....
}

End point:

 @PostMapping(value = "/payment/{unique_transaction_id}", consumes = { MediaType.APPLICATION_JSON_VALUE }, produces = { MediaType.APPLICATION_JSON_VALUE })
      public ResponseEntity<StringResponseDTO> handleWpfMessage(@PathVariable("unique_transaction_id") String unique_transaction_id,
          @RequestBody WpfPaymentsDTO transaction, BindingResult result, HttpServletRequest request) throws Exception {

        if (result.hasErrors()) {
            List<String> errors = result.getAllErrors().stream()
              .map(DefaultMessageSourceResolvable::getDefaultMessage)
              .collect(Collectors.toList());
            return new ResponseEntity<>(errors, HttpStatus.OK);
        } 

        return ResponseEntity.ok(new StringResponseDTO("test"));
      }

When use submits Angular form I would like to validate all fields. But currently I get this error: Cannot infer type arguments for ResponseEntity<>

What is the proper wya to implement this?

hovanessyan :

You are missing the @Valid annotation in your method signature. If you look at the example you are quoting, you will see that it's used on the User object.

So in your case:

@Valid @RequestBody WpfPaymentsDTO transaction

Also you are returning two different class types in ResponseEntity<T>

1) ResponseEntity<StringResponseDTO> in a validation successful scenario

2) ResponseEntity<List<String>> in a validation failure scenario

The above is the reason for:

But currently I get this error: Cannot infer type arguments for ResponseEntity<>

If you look at the example you are quoting, the method return type is ResponseEntity<Object>.

So your method should change to:

  @PostMapping(value = "/payment/{unique_transaction_id}", 
     consumes = { MediaType.APPLICATION_JSON_VALUE }, 
     produces = { MediaType.APPLICATION_JSON_VALUE })
  public ResponseEntity<Object> handleWpfMessage(
                 @PathVariable("unique_transaction_id") String unique_transaction_id,
                 @Valid @RequestBody WpfPaymentsDTO transaction, 
                 BindingResult result, 
                 HttpServletRequest request) throws Exception {

Update:

Is there a way to find out for which variable the validation error is raised?

Yes, you can get all field binding errors like this:

List<FieldError> errors = bindingResult.getFieldErrors();
for (FieldError error : errors ) {
    System.out.println ("Validation error in field: " + error.getField() 
                    + "! Validation error message: " + error.getDefaultMessage() 
                    + "! Rejected value:" + error.getRejectedValue());
}