Я уже смотрелаЗапись файлов в Blobstore (Experimental) " на странице движка приложения Google.

Вот что у меня есть:

// Get a file service
  FileService fileService = FileServiceFactory.getFileService();

  // Create a new Blob file with mime-type "text/plain"
  AppEngineFile file = fileService.createNewBlobFile("text/plain");

  // Open a channel to write to it
  boolean lock = false;
  FileWriteChannel writeChannel = fileService.openWriteChannel(file, lock);

  // Different standard Java ways of writing to the channel
  // are possible. Here we use a PrintWriter:
  **PrintWriter** out = new PrintWriter(Channels.newWriter(writeChannel, "UTF8"));
  out.println("The woods are lovely dark and deep.");
  out.println("But I have promises to keep.");

  // Close without finalizing and save the file path for writing later
  out.close();
  String path = file.getFullPath();

  // Write more to the file in a separate request:
  file = new AppEngineFile(path);

  // This time lock because we intend to finalize
  lock = true;
  writeChannel = fileService.openWriteChannel(file, lock);

  // This time we write to the channel directly
  writeChannel.write(ByteBuffer.wrap
            ("And miles to go before I sleep.".getBytes()));

  // Now finalize
  writeChannel.closeFinally();

  // Later, read from the file using the file API
  lock = false; // Let other people read at the same time
  FileReadChannel readChannel = fileService.openReadChannel(file, false);

  // Again, different standard Java ways of reading from the channel.
  BufferedReader reader =
          new BufferedReader(Channels.newReader(readChannel, "UTF8"));
       String line = reader.readLine();
  // line = "The woods are lovely dark and deep."

  readChannel.close();

  // Now read from the file using the Blobstore API
  BlobKey blobKey = fileService.getBlobKey(file);
  BlobstoreService blobStoreService = BlobstoreServiceFactory.getBlobstoreService();
  String segment = new String(blobStoreService.fetchData(blobKey, 30, 40));

К сожалению, это только для текстового файла. Я бы предположил, чтоPrintWriter следует изменить наImageWriter но в Google App Engine,ImageWriter не поддерживается. Что я должен делать?