Spring不会进入自定义验证器

public class UserValidator implements Validator {

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

    @Override
    public void validate(Object target, Errors errors) {
        ValidationUtils.rejectIfEmptyOrWhitespace(errors, "username", "NotEmpty");
        ValidationUtils.rejectIfEmptyOrWhitespace(errors, "password", "NotEmpty");
        
        User user = (User) target;
        
        if (user.getUsername().length() < 6 || user.getUsername().length() > 20) {
            errors.rejectValue("username", "Size.userForm.username");
        }
        
        // 其他验证逻辑...
    }
}

@Controller
public class UserController {

    @Autowired
    private UserValidator userValidator;

    @InitBinder
    protected void initBinder(WebDataBinder binder) {
        binder.addValidators(userValidator);
    }

    @PostMapping("/register")
    public String register(@ModelAttribute("user") User user, BindingResult result) {
        if (result.hasErrors()) {
            return "register";
        }
        
        // 处理注册逻辑...
        
        return "redirect:/login";
    }
}