A short code snippet showing how to write data to the Blobstore using the experimental Files API.
FileService file_service = FileServiceFactory.getFileService();
AppEngineFile file = file_service.createNewBlobFile(mime_type, filename);
FileWriteChannel write_channel = file_service.openWriteChannel(file, true);
ByteBuffer buffer = ByteBuffer.wrap(byte_array);
write_channel.write(buffer);
write_channel.closeFinally();