Spring Validation 다양한 처리 방법

@PostMapping(value = "/leave")
public String applyLeave(@ModelAttribute @Valid RequestDto dto,
                          Errors erros, RedirectAttributes redirectAttributes) {

    boolean isValid = validatorObject.validate(dto, erros);
    if (!isValid || erros.hasErrors()) {
        redirectAttributes.addFlashAttribute("alertMsg", erros);
        return "redirect:/member/v1/leave";
    }
    ...
}

public class ValidatorObject implements ControllerValidator {

    @Override
    public boolean validate(Object requestDTO, Errors errors) {
        // TODO
    }
}

@Documented
@Constraint(validatedBy = SortColumnTypeValidator.class)
@Target({ElementType.METHOD, ElementType.FIELD, PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
public @interface Target {

    // 애노테이션 지정 시 validatino rule에 맞는 메시지 지정 가능!!!
    String message() default "사용 예시) sort=title,asc or sort=title,name,desc or sort=title,desc&sort=name,asc";

    String[] names() default {};

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};

    @Target({METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER, TYPE_USE})
    @Retention(RUNTIME)
    @Documented
    @interface List {
        NotBlank[] value();
    }
}

public class TargetValidator implements ConstraintValidator<Target, String> {

    @Override
    public void initialize(Target target) {
    
    }
 
    @Override
    public boolean isValid(String field, ConstraintValidatorContext cxt) {
        return field != null && field.matches("[0-9]+")
                && (field.length() > 8) && (field.length() < 14);
    }
}