[EA3-126] refactor: 파일 업로드 유효성 및 GCS 메모리 효율 개선

Author: endorsement0912

src/main/java/grep/neogul_coder/global/utils/upload/AbstractFileManager.java

@@ -32,6 +32,11 @@ public FileUploadResponse upload(MultipartFile file, Long uploaderId, FileUsageT
       throw new FileUploadException(FileUploadErrorCode.FILE_EMPTY);
     }
 
+    String contentType = file.getContentType();
+    if(contentType == null || !ALLOWED_TYPES.contains(contentType)) {
+      throw new FileUploadException(FileUploadErrorCode.FILE_TYPE_INVALID);
+    }
+
     String originFileName = file.getOriginalFilename();
     if (originFileName == null) {
       throw new FileUploadException(FileUploadErrorCode.FILE_NAME_INVALID);
@@ -88,4 +93,9 @@ protected String generateRenameFileName(String originFileName) {
   protected String buildFullPath(String savePath, String renameFileName) {
     return savePath + "/" + renameFileName;
   }
+
+  // MIME 타입 허용 목록 (이미지 파일만 허용)
+  protected static final List<String> ALLOWED_TYPES = List.of(
+      "image/png", "image/jpeg", "image/jpg", "image/gif", "image/webp"
+  );
 }

src/main/java/grep/neogul_coder/global/utils/upload/uploader/GcpFileUploader.java

@@ -8,6 +8,7 @@
 import grep.neogul_coder.global.utils.upload.AbstractFileManager;
 import grep.neogul_coder.global.utils.upload.exception.FileUploadErrorCode;
 import java.io.IOException;
+import java.io.InputStream;
 import lombok.extern.slf4j.Slf4j;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.context.annotation.Profile;
@@ -27,13 +28,13 @@ public class GcpFileUploader extends AbstractFileManager {
   // GCP Cloud Storage 에 파일을 업로드
   @Override
   protected void uploadFile(MultipartFile file, String fullPath) throws IOException {
-    try {
+    try (InputStream inputStream = file.getInputStream()) {
       Storage storage = StorageOptions.getDefaultInstance().getService();
       BlobId blobId = BlobId.of(bucket, fullPath);
       BlobInfo blobInfo = BlobInfo.newBuilder(blobId)
           .setContentType(file.getContentType())
           .build();
-      storage.create(blobInfo, file.getBytes());
+      storage.createFrom(blobInfo, inputStream);
     } catch (IOException e) {
       log.error("GCP 파일 업로드 실패 - 원본 파일명: {}", file.getOriginalFilename(), e);
       throw new FileUploadException(FileUploadErrorCode.GCP_UPLOAD_FAIL, e);