refactor : 최상위 keyword인지 도메인에서 판단하기

#1461

Author: java-saeng

backend/src/main/java/wooteco/prolog/roadmap/application/RoadMapService.java

@@ -1,11 +1,14 @@
 package wooteco.prolog.roadmap.application;
 
+import static wooteco.prolog.common.exception.BadRequestCode.CURRICULUM_NOT_FOUND_EXCEPTION;
+
 import java.util.List;
 import java.util.Set;
 import java.util.stream.Collectors;
 import lombok.RequiredArgsConstructor;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
+import wooteco.prolog.common.exception.BadRequestException;
 import wooteco.prolog.roadmap.application.dto.KeywordsResponse;
 import wooteco.prolog.roadmap.domain.Curriculum;
 import wooteco.prolog.roadmap.domain.Keyword;
@@ -26,8 +29,7 @@ public class RoadMapService {
     @Transactional(readOnly = true)
     public KeywordsResponse findAllKeywords(final Long curriculumId) {
         final Curriculum curriculum = curriculumRepository.findById(curriculumId)
-            .orElseThrow(() -> new IllegalArgumentException(
-                "해당 커리큘럼이 존재하지 않습니다. curriculumId = " + curriculumId));
+            .orElseThrow(() -> new BadRequestException(CURRICULUM_NOT_FOUND_EXCEPTION));
 
         final Set<Long> sessionIds = sessionRepository.findAllByCurriculumId(curriculum.getId())
             .stream()

backend/src/main/java/wooteco/prolog/roadmap/application/dto/KeywordsResponse.java

@@ -26,7 +26,7 @@ public static KeywordsResponse createResponse(final List<Keyword> keywords) {
 
     public static KeywordsResponse createResponseWithChildren(final List<Keyword> keywords) {
         List<KeywordResponse> keywordsResponse = keywords.stream()
-            .filter(it -> it.getParent() == null)
+            .filter(Keyword::isRoot)
             .map(KeywordResponse::createWithAllChildResponse)
             .collect(Collectors.toList());
         return new KeywordsResponse(keywordsResponse);

backend/src/main/java/wooteco/prolog/roadmap/domain/Keyword.java

@@ -124,6 +124,10 @@ private void validateKeywordParent(final Keyword parentKeyword) {
         }
     }
 
+    public boolean isRoot() {
+        return parent == null;
+    }
+
     public Long getParentIdOrNull() {
         if (parent == null) {
             return null;