[fix] recommend API 수정

src/main/java/com/umc/bscene/domain/band/controller/BandController.java

@@ -59,13 +59,15 @@ public ResponseEntity<SuccessResponse<BandResponse>> createBand(
     }
 
     // 밴드 추천 목록 조회 API
+    // withDummy=false면 더미 밴드(운영 DB 시드 id 1~474)를 추천 후보에서 제외, 생략·true면 전체 (기존 호환)
     @GetMapping("/recommendations")
     public ResponseEntity<SuccessResponse<BandRecommendResponse>> getRecommendedBands(
             @AuthenticationPrincipal AuthMember authMember,
             @RequestParam(required = false) Long cursor,
-            @RequestParam(required = false) Integer size
+            @RequestParam(required = false) Integer size,
+            @RequestParam(defaultValue = "true") boolean withDummy
     ) {
-        BandRecommendResponse response = bandRecommendationService.getRecommendedBands(authMember.getUser().getId(), cursor, size);
+        BandRecommendResponse response = bandRecommendationService.getRecommendedBands(authMember.getUser().getId(), cursor, size, withDummy);
         SuccessResponse<BandRecommendResponse> successResponse = SuccessResponse.of(
                 response,
                 BandSuccessCode.BAND_RECOMMEND_LIST_GET_SUCCESS

src/main/java/com/umc/bscene/domain/band/service/BandRecommendationService.java

@@ -4,5 +4,10 @@
 
 public interface BandRecommendationService {
 
-    BandRecommendResponse getRecommendedBands(Long userId, Long cursor, Integer size);
+    BandRecommendResponse getRecommendedBands(Long userId, Long cursor, Integer size, boolean withDummy);
+
+    // withDummy 생략 호출은 더미 밴드를 포함한 기존 동작을 유지한다 (팬홈 등 기존 호출부 호환)
+    default BandRecommendResponse getRecommendedBands(Long userId, Long cursor, Integer size) {
+        return getRecommendedBands(userId, cursor, size, true);
+    }
 }

src/main/java/com/umc/bscene/domain/band/service/impl/BandRecommendationServiceV1Impl.java

@@ -44,6 +44,9 @@ public class BandRecommendationServiceV1Impl implements BandRecommendationServic
     private static final int RECENT_POST_SCORE = 2;
     private static final int RECENT_PERFORMANCE_SCORE = 1;
 
+    // 더미 밴드 경계 : 운영 DB 시드 기준으로 이 값 이하 band id는 전부 더미 밴드 (withDummy=false 필터의 기준)
+    private static final long DUMMY_BAND_MAX_ID = 474;
+
     private final BandRepository bandRepository;
     private final UserRepository userRepository;
     private final UserGenresRepository userGenresRepository;
@@ -53,7 +56,7 @@ public class BandRecommendationServiceV1Impl implements BandRecommendationServic
 
     // 밴드 추천 목록 조회 (장르/지역/활동 내역 기반 스코어링)
     @Override
-    public BandRecommendResponse getRecommendedBands(Long userId, Long cursor, Integer size) {
+    public BandRecommendResponse getRecommendedBands(Long userId, Long cursor, Integer size, boolean withDummy) {
         int pageSize = (size != null) ? size : DEFAULT_RECOMMEND_PAGE_SIZE;
         long offset = (cursor != null) ? cursor : 0;
 
@@ -67,7 +70,9 @@ public BandRecommendResponse getRecommendedBands(Long userId, Long cursor, Integ
                 .map(UserRegions::getRegion)
                 .collect(Collectors.toSet());
 
-        List<Band> candidates = bandRepository.findAllByStatus(BandStatus.ACCEPTED);
+        List<Band> candidates = bandRepository.findAllByStatus(BandStatus.ACCEPTED).stream()
+                .filter(band -> withDummy || band.getId() > DUMMY_BAND_MAX_ID)
+                .toList();
         List<Long> candidateIds = candidates.stream().map(Band::getId).toList();
 
         LocalDateTime postSince = LocalDateTime.now().minusDays(RECENT_ACTIVITY_DAYS);

src/main/java/com/umc/bscene/domain/band/service/impl/BandRecommendationServiceV2Impl.java

@@ -57,6 +57,9 @@ public class BandRecommendationServiceV2Impl implements BandRecommendationServic
     private static final int RECENT_ACTIVITY_DAYS = 30;
     private static final int TOP_CLICKED_BANDS_LIMIT = 10;
 
+    // 더미 밴드 경계 : 운영 DB 시드 기준으로 이 값 이하 band id는 전부 더미 밴드 (withDummy=false 필터의 기준)
+    private static final long DUMMY_BAND_MAX_ID = 474;
+
     // explicit(장르/지역/활동) 내부 가중치. 셋 다 만족 시 explicit 원점수는 GENRE+REGION+ACTIVITY(=6)로 정규화된다.
     private static final double GENRE_MATCH_SCORE = 3;
     private static final double REGION_MATCH_SCORE = 2;
@@ -129,7 +132,7 @@ public class BandRecommendationServiceV2Impl implements BandRecommendationServic
     private final BandRecommendationLogRepository bandRecommendationLogRepository;
 
     @Override
-    public BandRecommendResponse getRecommendedBands(Long userId, Long cursor, Integer size) {
+    public BandRecommendResponse getRecommendedBands(Long userId, Long cursor, Integer size, boolean withDummy) {
         int limit = (size != null) ? Math.min(size, RECOMMEND_LIMIT) : RECOMMEND_LIMIT;
 
         User user = userRepository.getReferenceById(userId);
@@ -184,6 +187,11 @@ public BandRecommendResponse getRecommendedBands(Long userId, Long cursor, Integ
                 : ColdStartFallback.EMPTY;
         coldStartFallback.bands().forEach(band -> candidateBands.put(band.getId(), band));
 
+        // withDummy=false : 더미 밴드(경계 이하 id) 제외
+        if (!withDummy) {
+            candidateBands.keySet().removeIf(id -> id <= DUMMY_BAND_MAX_ID);
+        }
+
         List<Long> candidateIds = new ArrayList<>(candidateBands.keySet());
 
         // 노출 피로도 감점 : 후보에서 빼지 않고 점수만 깎는다 (FLOOR 덕에 유일한 매치는 그대로 남음).

src/test/java/com/umc/bscene/domain/band/service/BandRecommendationServiceV1ImplTest.java

@@ -174,4 +174,29 @@ private void preferredGenreAndRegion(Genre genre, Region region) {
 
         assertTrue(response.bands().isEmpty());
     }
+
+    @Test
+    void withDummy가_false면_더미_밴드_id는_후보에서_제외된다() {
+        preferredGenreAndRegion(Genre.HARD_ROCK, Region.SEOUL);
+        Band dummyBand = band(474L, Genre.HARD_ROCK, Region.SEOUL); // 더미 경계(<=474)
+        Band realBand = band(475L, Genre.HARD_ROCK, Region.SEOUL);
+        when(bandRepository.findAllByStatus(BandStatus.ACCEPTED)).thenReturn(List.of(dummyBand, realBand));
+
+        BandRecommendResponse response = service.getRecommendedBands(USER_ID, null, null, false);
+
+        assertEquals(1, response.bands().size());
+        assertEquals(475L, response.bands().get(0).bandId());
+    }
+
+    @Test
+    void withDummy_생략시_기본값true로_더미_밴드도_포함된다() {
+        preferredGenreAndRegion(Genre.HARD_ROCK, Region.SEOUL);
+        Band dummyBand = band(474L, Genre.HARD_ROCK, Region.SEOUL);
+        Band realBand = band(475L, Genre.HARD_ROCK, Region.SEOUL);
+        when(bandRepository.findAllByStatus(BandStatus.ACCEPTED)).thenReturn(List.of(dummyBand, realBand));
+
+        BandRecommendResponse response = service.getRecommendedBands(USER_ID, null, null);
+
+        assertEquals(2, response.bands().size());
+    }
 }

src/test/java/com/umc/bscene/domain/band/service/impl/BandRecommendationServiceV2ImplTest.java

@@ -123,6 +123,44 @@ void similarityBonusIsZeroWhenUserFollowsNoBand() {
         verify(bandSimilarityRepository, never()).findByBandIdIn(anyList());
     }
 
+    @Test
+    void withDummyDefaultsToTrueAndIncludesDummyBands() {
+        when(followRepository.findBandIdsByUserId(USER_ID)).thenReturn(List.of());
+        when(userGenresRepository.findAllByUser(any(User.class)))
+                .thenReturn(List.of(UserGenres.builder().genre(Genre.HARD_ROCK).build()));
+        when(userRegionsRepository.findAllByUser(any(User.class))).thenReturn(List.of());
+
+        Band dummyBand = band(474L, Genre.HARD_ROCK, Region.SEOUL);
+        Band realBand = band(475L, Genre.HARD_ROCK, Region.SEOUL);
+        when(bandRepository.findByGenreIn(any())).thenReturn(List.of(dummyBand, realBand));
+        when(postRepository.findBandIdsWithRecentPost(anyList(), any())).thenReturn(List.of());
+        when(postRepository.findLatestActivityAtByBandIds(anyList())).thenReturn(List.of());
+
+        // withDummy 생략 -> 기본값 true, 더미 밴드도 그대로 포함
+        BandRecommendResponse response = service.getRecommendedBands(USER_ID, null, null);
+
+        assertEquals(2, response.bands().size());
+    }
+
+    @Test
+    void withDummyFalseExcludesDummyBands() {
+        when(followRepository.findBandIdsByUserId(USER_ID)).thenReturn(List.of());
+        when(userGenresRepository.findAllByUser(any(User.class)))
+                .thenReturn(List.of(UserGenres.builder().genre(Genre.HARD_ROCK).build()));
+        when(userRegionsRepository.findAllByUser(any(User.class))).thenReturn(List.of());
+
+        Band dummyBand = band(474L, Genre.HARD_ROCK, Region.SEOUL);
+        Band realBand = band(475L, Genre.HARD_ROCK, Region.SEOUL);
+        when(bandRepository.findByGenreIn(any())).thenReturn(List.of(dummyBand, realBand));
+        when(postRepository.findBandIdsWithRecentPost(anyList(), any())).thenReturn(List.of());
+        when(postRepository.findLatestActivityAtByBandIds(anyList())).thenReturn(List.of());
+
+        BandRecommendResponse response = service.getRecommendedBands(USER_ID, null, null, false);
+
+        assertEquals(1, response.bands().size());
+        assertEquals(475L, response.bands().get(0).bandId());
+    }
+
     @Test
     void similarityAverageIsCappedBeforeNormalizing() {
         List<Long> followedBandIds = List.of(100L, 200L, 300L);