ModelValidator.java

import org.springframework.stereotype.Service;

import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import javax.validation.ValidatorFactory;
import java.util.Collection;
import java.util.List;
import java.util.stream.Collectors;

@Service
public class ModelValidator {

    private final ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
    private final Validator validator = factory.getValidator();

    public <T> void validate(T model) {
        Collection<ConstraintViolation<T>> violations = validator.validate(model);
        if (violations.isEmpty()) {
            return;
        }
        final List<String> errorMessages = violations
                .stream()
                .map(c -> c.getPropertyPath() + " " + c.getMessage())
                .collect(Collectors.toList());
        throw new ValidationException(errorMessages);
    }
}