Fatal error: require(): Failed opening required Hydrator in mongodb

I was working on putting POPO to MongoDB in symfony project.
I have the Document inside BundleDocumentMyDocument.php

I want to create this document for the first time, but would like to update the document if it exists based on its two fields like:
* I have taken out some of additional information and focus on the main code only..

$file_id = getTheFileId();
$accessor_id = getAccessorId();
			$file_access=$repository->findOneBy(array('fileId'=>$file_id, 'accessorId'=>$accessor_id));
			if ($file_access && $file_access instanceof FileAccess){
				$file_access=new FileAccess();

The problem I was facing was when I try to access the record, not when I was adding it.
and I know the record was there by using the command line mongo tool

The solution appears to be the missing config item for mongo:
on your config for mongo add

auto_generate_hydrator_classes: true

and that should fix the problem.