refactor: 텃밭 id 목록 조회 수정

src/main/java/com/example/cp_main_be/domain/member/user/domain/repository/UserRepository.java

@@ -4,12 +4,17 @@
 import java.util.Optional;
 import java.util.UUID;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
 
 public interface UserRepository extends JpaRepository<User, Long> {
 
   Optional<User> findByNickname(String username);
 
   Optional<User> findByUuid(UUID uuid);
 
+  @Query("SELECT u FROM User u LEFT JOIN FETCH u.gardens WHERE u.id = :userId")
+  Optional<User> findByIdWithGardens(@Param("userId") Long userId);
+
   Boolean existsByNickname(String nickname);
 }

src/main/java/com/example/cp_main_be/domain/member/user/presentation/UserController.java

@@ -1,6 +1,5 @@
 package com.example.cp_main_be.domain.member.user.presentation;
 
-import com.example.cp_main_be.domain.garden.garden.domain.Garden;
 import com.example.cp_main_be.domain.member.user.domain.User;
 import com.example.cp_main_be.domain.member.user.domain.repository.UserRepository;
 import com.example.cp_main_be.domain.member.user.dto.request.AvatarChangeRequest;
@@ -14,9 +13,7 @@
 import io.swagger.v3.oas.annotations.tags.Tag;
 import jakarta.validation.Valid;
 import jakarta.websocket.server.PathParam;
-import java.util.Comparator;
 import java.util.List;
-import java.util.stream.Collectors;
 import lombok.RequiredArgsConstructor;
 import org.springframework.http.ResponseEntity;
 import org.springframework.security.core.annotation.AuthenticationPrincipal;
@@ -90,12 +87,8 @@ public ResponseEntity<ApiResponse<UserRegisterResponse.LevelStatusResponseDTO>>
   @GetMapping("/me/gardens")
   public ResponseEntity<ApiResponse<List<Long>>> getMyGardenIds(
       @AuthenticationPrincipal User user) {
-    List<Long> gardenIds =
-        user.getGardens().stream()
-            .sorted(Comparator.comparing(Garden::getSlotNumber))
-            .map(Garden::getId)
-            .collect(Collectors.toList());
-
+    // 로직을 서비스 계층으로 위임하여 트랜잭션 내에서 처리하도록 변경
+    List<Long> gardenIds = userService.getMyGardenIds(user);
     return ResponseEntity.ok(ApiResponse.success(gardenIds));
   }
 

src/main/java/com/example/cp_main_be/domain/member/user/service/UserService.java

@@ -128,6 +128,26 @@ public User getCurrentUser() {
     throw new IllegalArgumentException("인증 정보를 찾을 수 없습니다.");
   }
 
+  /**
+   * 사용자의 모든 텃밭 ID 목록을 슬롯 번호 순으로 정렬하여 반환합니다.
+   *
+   * @param user 현재 로그인한 사용자
+   * @return 정렬된 텃밭 ID 목록
+   */
+  @Transactional(readOnly = true)
+  public List<Long> getMyGardenIds(User user) {
+    // LazyInitializationException을 방지하기 위해 Fetch Join으로 User와 gardens를 함께 조회
+    User managedUser =
+        userRepository
+            .findByIdWithGardens(user.getId())
+            .orElseThrow(() -> new UserNotFoundException("사용자를 찾을 수 없습니다."));
+
+    return managedUser.getGardens().stream()
+        .sorted(Comparator.comparing(Garden::getSlotNumber))
+        .map(Garden::getId)
+        .collect(Collectors.toList());
+  }
+
   /**
    * 특정 유저의 프로필 정보를 조회합니다.
    *