java - Spring MVC validator annotation + custom validation

Question

I'm working on spring mvc application, where I should aplly validation based on Spring MVC validator. I first step for that I added annotation for class and setup controller and it works fine. And now I need to implement custom validator for perform complex logic, but i want to use existing annotation and just add additional checking.

My User class:

public class User
{
    @NotEmpty
    private String name;

    @NotEmpty
    private String login; // should be unique
}

My validator:

@Component
public class UserValidator implements Validator
{

    @Autowired
    private UserDAO userDAO;

    @Override
    public boolean supports(Class<?> clazz)
    {
        return User.class.equals(clazz) || UsersForm.class.equals(clazz);
    }

    @Override
    public void validate(Object target, Errors errors)
    {
        /*
        ValidationUtils.rejectIfEmptyOrWhitespace(errors, "name", "NotEmpty.user");
        ValidationUtils.rejectIfEmptyOrWhitespace(errors, "login", "NotEmpty.user");
        */
        User user = (User) target;
        if (userDAO.getUserByLogin(user.getLogin()) != null) {
            errors.rejectValue("login", "NonUniq.user");
        }
    }
}

My controller:

@Controller
public class UserController
{
    @Autowired
    private UserValidator validator;

    @InitBinder
    protected void initBinder(final WebDataBinder binder)
    {
        binder.setValidator(validator);
    }

    @RequestMapping(value = "/save")
    public ModelAndView save(@Valid @ModelAttribute("user") final User user,
            BindingResult result) throws Exception
    {
        if (result.hasErrors())
        {
            // handle error
        } else
        {
            //save user
        }
    }
}

So, Is it possible to use custom validator and annotation together? And if yes how?

Answer 1

I know this is a kind of old question but, for googlers...

you should use addValidators instead of setValidator. Like following:

@InitBinder
protected void initBinder(final WebDataBinder binder) {
    binder.addValidators(yourCustomValidator, anotherValidatorOfYours);
}

PS: addValidators accepts multiple parameters (ellipsis)

if you checkout the source of org.springframework.validation.DataBinder you will see:

public class DataBinder implements PropertyEditorRegistry, TypeConverter {

    ....

    public void setValidator(Validator validator) {
        assertValidators(validator);
        this.validators.clear();
        this.validators.add(validator);
    }

    public void addValidators(Validator... validators) {
        assertValidators(validators);
        this.validators.addAll(Arrays.asList(validators));
    }

    ....

}

as you see setValidator clears existing (default) validator so @Valid annotation won't work as expected.