[Refactor] 좋아요 동시 요청 충돌 처리 공통화

[pooreumjung]

🧾 요약

• PostLikeService와 CourseLikeService에 중복된 동시 요청 충돌 처리 패턴을 LikeConflictHandler로 통합

🔗 이슈

• close [refactor] PostLikeService/CourseLikeService 동시 요청 처리 패턴 통합 #174

✨ 변경 내용

• LikeConflictHandler 유틸 추가 — 좋아요 생성 충돌을 멱등하게 처리하는 공통 헬퍼
• PostLikeService, CourseLikeService의 DataIntegrityViolationException catch 블록을 LikeConflictHandler로 교체
• LikeConflictHandlerTest 추가 — 정상 생성 / 충돌 감지 / 타 예외 전파 경로 검증

✅ 확인

• 빌드 OK
• 테스트 OK

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✨ Finishing Touches

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• Create PR with unit tests
• Commit unit tests in branch refactor/#174-like-conflict-handler

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[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

본 PR은 좋아요 기능에서 발생하는 동시성 이슈 처리 로직을 공통화하여 코드의 유지보수성을 높이고 중복을 제거하는 것을 목적으로 합니다. 기존에 서비스 레이어마다 개별적으로 구현되어 있던 예외 처리 패턴을 유틸리티 클래스로 분리함으로써, 향후 유사한 충돌 상황 발생 시 일관된 방식으로 대응할 수 있도록 개선하였습니다.

Highlights

• LikeConflictHandler 유틸리티 추가: 좋아요 생성 시 발생하는 동시 요청 충돌(DataIntegrityViolationException)을 멱등하게 처리하기 위한 공통 유틸리티 클래스를 도입했습니다.
• 서비스 로직 리팩토링: PostLikeService와 CourseLikeService에서 중복되던 예외 처리 로직을 LikeConflictHandler를 사용하도록 개선하여 코드 중복을 제거했습니다.
• 테스트 코드 추가: LikeConflictHandler에 대한 단위 테스트를 추가하여 정상 동작, 충돌 감지, 예외 전파 시나리오를 검증했습니다.

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[gemini-code-assist]

Code Review

This pull request introduces a utility class LikeConflictHandler to handle concurrent creation conflicts and refactors PostLikeService and CourseLikeService to use it, reducing code duplication. Unit tests for the new handler are also added. The review feedback highlights critical issues regarding JPA's write-behind behavior, suggesting the use of saveAndFlush instead of save to ensure DataIntegrityViolationException is caught correctly during execution. Additionally, for PostLikeService, it is recommended to wrap the notification call in a try-catch block to prevent external side-effect failures from rolling back the main transaction.

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