spring-cloud-gcp/Lobby

Can you guys help me on my concern? I want to upload the file in GCP to gs://bucket-name/folder/subfolder/file.xxx

public ResponseEntity uploadFileToConversation(MultipartFile multipartFile, String conversationId, String userId, String userName) throws IOException {
        File file = new File();
        file.setFileName(multipartFile.getOriginalFilename());
        file.setDateCreated(new Date());
        file.setFileType(multipartFile.getContentType());
        Long fileSize = multipartFile.getSize() / 1024;
        file.setSize(fileSize.toString());
        file.setUserId(userId);

        java.io.File convertedFile = convertMultiPartToFile(multipartFile);
        Path filePath = convertedFile.toPath();
        String objectName = generateFileName(multipartFile);

        Storage storage = StorageOptions.getDefaultInstance().getService();

        BlobId blobId = BlobId.of(firebaseBucket + "/folder/subfolder/", objectName);
        BlobInfo blobInfo = BlobInfo.newBuilder(blobId).build();
        Blob blob = storage.create(blobInfo, Files.readAllBytes(filePath));

        System.out.println("File " + filePath + " uploaded to bucket " + firebaseBucket + " as " + objectName);

        return ResponseEntity.ok().body(file);
    }

But the console returning me that my bucket name is invalid

2020-10-22 10:15:07.156 ERROR 5552 --- [0.0-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is com.google.cloud.storage.StorageException: Invalid bucket name: 'messaging-app-55f65.appspot.com/folder/subfolder/'] with root cause

com.google.api.client.googleapis.json.GoogleJsonResponseException: 400 Bad Request
POST https://storage.googleapis.com/upload/storage/v1/b/messaging-app-55f65.appspot.com%2Ffolder%2Fsubfolder%2F/o?projection=full&uploadType=multipart
{
  "code" : 400,
  "errors" : [ {
    "domain" : "global",
    "message" : "Invalid bucket name: 'messaging-app-55f65.appspot.com/folder/subfolder/'",
    "reason" : "invalid"
  } ],
  "message" : "Invalid bucket name: 'messaging-app-55f65.appspot.com/folder/subfolder/'"
}

I hope you can enlighten me on this one.