Spring validator class does not validate the Dto data

Andrew T :

I am implementing a microservice which has only to validate Transaction from the request body, and if it is valid, send it to the next microservice. I have implemented the Validator, but it does not seem to work

Transaction DTO:

public class Transaction {

    private TransactionType transactionType;
    private String iban;
    private String CNP;
    private String name;
    private String description;
    private Float sum;
    ...
}

The Validator:

@Component()
public class TransactionValidation implements Validator {
    @Override
    public boolean supports(Class<?> aClass) {
        return Transaction.class.equals(aClass);
    }

    @Override
    public void validate(Object object, Errors errors) {
        Transaction transaction = (Transaction) object;
        if(!isValidCnp(transaction.getCNP())){
            errors.rejectValue("CNP", "CNP validation error");
        }

        if(!isValidIban(transaction.getIban())){
            errors.rejectValue("IBAN", "IBAN validation error");
        }

        if(isInputStringEmpty(transaction.getName())){
            errors.rejectValue("name", "Name validation error");
        }
    }
    ...
}

The Controller does nothing but simply returns the transaction it receives:

@PostMapping()
public Transaction validateTransaction(@RequestBody @Valid Transaction transaction){
    return transaction;
}

But it does not seem to work, it seems that the app does not use the Validator implemented above. Why? Do I have to register my validator anywhere?

akk202 :

I believe the @Valid annotation works on JSR-303 validation spec with annotations in your DTO. You have 2 options

public class Transaction {
    @NonNull
    @NotEmpty
    @NumericIbanConstriant 
    private String iban;
}

@Constraint(validatedBy = NumericIbanConstriantValidator.class)
public @interface NumericIbanConstriant {
}

public NumericIbanConstriantValidator implements ConstraintValidator<NumericIbanConstraint, String> {
   // validation logic for iban string being numeric perhaps?
}

OR in your controller directly autowire the TransactionValidation and call "validate" passing in Transaction, and Errors object

@PostMapping()
public Transaction validateTransaction(@RequestBody Transaction transaction, Errors errors){
    transactionValidation.validate(transaction, errors);
    return transaction;
}