Validation

// 검증 로직
if (!StringUtils.hasText(item.getItemName())) {
    bindingResult.addError(new FieldError("item", "itemName", item.getItemName(), false, null, null, "상품 이름은 필수 입니다."));
}
if (item.getPrice() == null || item.getPrice() < 1000 || item.getPrice() > 1000000) {
    bindingResult.addError(new FieldError("item", "price", item.getPrice(), false, null, null, "가격은 1,000 ~ 1,000,000 까지 허용합니다."));
}
if (item.getQuantity() == null || item.getQuantity() >= 9999) {
    bindingResult.addError(new FieldError("item", "quantity", item.getQuantity(), false, null ,null, "수량은 최대 9,999 까지 허용합니다."));
}

// 특정 필드가 아닌 복합 룰 검증
if (item.getPrice() != null && item.getQuantity() != null) {
    int resultPrice = item.getPrice() * item.getQuantity();
    if (resultPrice < 10000) {
        bindingResult.addError(new ObjectError("item",null ,null, "가격 * 수량의 합은 10,000원 이상이어야 합니다. 현재 값 = " + resultPrice));
    }
}

ValidationUtils.rejectIfEmptyOrWhitespace(bindingResult, "itemName", "required");

public interface Validator {
    // 해당 검증기를 지원하는 지 확인 
    boolean supports(Class<?> clazz);
    
    // target: 검증 대상 객체, errors: BindingResult
    void validate(Object target, Errors errors);
}

@InitBinder
public void init(WebDataBinder dataBinder) {
 log.info("init binder {}", dataBinder);
 dataBinder.addValidators(itemValidator);
}

PostMapping("/add")
public String addItem(
      @Validated @ModelAttribute Item item,
      BindingResult bindingResult
) {
   if (bindingResult.hasErrors()) {
     log.info("errors={}", bindingResult);
     return "validation/v2/addForm";
   }
   //...
}

@Component
public class ItemValidator implements Validator {
   @Override
   public boolean supports(Class<?> clazz) {
    return Item.class.isAssignableFrom(clazz);
   }
   @Override
   public void validate(Object target, Errors errors) { //... }
}

@InitBinder("targetObject")
public void initTargetObject(WebDataBinder webDataBinder) {
    log.info("webDataBinder={}, target={}", webDataBinder, webDataBinder.getTarget());
    webDataBinder.addValidators(/*TargetObject 관련 검증기*/);
}

@InitBinder("sameObject")
public void initSameObject(WebDataBinder webDataBinder) {
    log.info("webDataBinder={}, target={}", webDataBinder, webDataBinder.getTarget());
    webDataBinder.addValidators(/*SameObject 관련 검증기*/);
}

@Component
public class CardValidator {
    
    public void registerValidate(CardDto.RegisterRequest request, Errors e) {}
    public void updateValidate(CardDto.RegisterRequest request, Errors e) {}
}

public class MemberDto {

  @NotEmpty(message = "{email.notempty}")
  private String email;

  // standard getter and setters
}

@Constraint(validatedBy = EmailValidator.class)
@Target(ElementType.FIELD)
@Retention(value = RetentionPolicy.RUNTIME)
@Documented
public @interface AdvisorEmail {
    String message() default "{com.dope.pro.validator.ValidEmail.message}";

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

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

public class DeleteContacts {
    @Min(1)
    private Collection<@Length(max = 64) @NotBlank String> uids;
}

@Constraint(validatedBy = EmailValidator.class)
@Target(ElementType.FIELD)
@Retention(value = RetentionPolicy.RUNTIME)
@Documented
public @interface AdvisorEmail {
    String message() default "{com.dope.pro.validator.ValidEmail.message}";

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

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

@Component
public class AdvisorEmailValidator implements ConstraintValidator<AdvisorEmail, String> {
    private final List<String> HOSTS = List.of("dope.com");

    @Override
    public void initialize(AdvisorEmail constraintAnnotation) {
        ConstraintValidator.super.initialize(constraintAnnotation);
    }

    @Override
    public boolean isValid(String value, ConstraintValidatorContext context) {
        // Do Something
    }
}

public interface ItemValidationGroup {
    interface Create {}
    interface Update {}
}


public interface UpdateCheck {
}

@Data
@NoArgsConstructor
public class Item {

    @NotNull(groups = ItemValidationGroup.Update.class) 
    private Long id;

    @NotBlank(groups = {ItemValidationGroup.Create.class, ItemValidationGroup.Update.class})
    private String itemName;
}

@PostMapping
public String create(
        @Validated(ItemValidationGroup.Create.class) @ModelAttribute Item item, 
        BindingResult bindingResult, 
) {}

@GroupSequence({
        CardValidationSequence.ExpireMonth.class,
        CardValidationSequence.ExpireYear.class,
        CardValidationSequence.CardNumber.class,
})
public interface CardValidationGroup {
    interface ExpireMonth {
    }

    interface ExpireYear {
    }

    interface CardNumber {
    }
}

@UtilityClass
public class ValidationErrorExtractor {

  public static String getResultMessage(MethodArgumentNotValidException e) {
    BindingResult bindingResult = e.getBindingResult();

    final StringBuilder resultMessageBuilder = new StringBuilder();
    
    // Field Errors
    final Iterator<FieldError> fieldErrorIterator = bindingResult.getFieldErrors().iterator();
    while (fieldErrorIterator.hasNext()) {
      final FieldError fieldError = fieldErrorIterator.next();
      resultMessageBuilder
              .append("[")
              .append(fieldError.getField())
              .append("' is '")
              .append(fieldError.getRejectedValue())
              .append("'. ")
              .append(fieldError.getDefaultMessage())
              .append("]");

      if (fieldErrorIterator.hasNext()) {
        resultMessageBuilder.append(", ");
      }
    }

    // Other Errors
    final Iterator<ObjectError> objectErrorIterator = bindingResult.getAllErrors().iterator();
    while (objectErrorIterator.hasNext()) {
      ObjectError objectError = objectErrorIterator.next();
      resultMessageBuilder
              .append("[")
              .append(objectError.getObjectName())
              .append("' is '")
              .append(objectError.getCode())
              .append("'. ")
              .append(objectError.getDefaultMessage())
              .append("]");

      if (objectErrorIterator.hasNext()) {
        resultMessageBuilder.append(", ");
      }
    }

    return resultMessageBuilder.toString();
  }  
    
  public String getResultMessage(ConstraintViolationException e) {
    final Iterator<ConstraintViolation<?>> violationIterator = e.getConstraintViolations().iterator();
    final StringBuilder resultMessageBuilder = new StringBuilder();
    
    while (violationIterator.hasNext() == true) {
      final ConstraintViolation<?> constraintViolation = violationIterator.next();
      resultMessageBuilder
              .append("['")
              .append(getPopertyName(constraintViolation.getPropertyPath().toString()))
              .append("' is '")
              .append(constraintViolation.getInvalidValue())
              .append("'. ")
              .append(constraintViolation.getMessage())
              .append("]");

      if (violationIterator.hasNext() == true) {
        resultMessageBuilder.append(", ");
      }
    }

    return resultMessageBuilder.toString();
  }

  private String getPropertyName(String propertyPath) {
    return propertyPath.substring(propertyPath.lastIndexOf('.') + 1);
  }
}