title: Can I use String as ID type for mongodb document?
body: <p>I am using java/morphia to deal with mongodb. The default ObjectId is not very convenient to use from Java layer. I would like to make it a String type while keep the key generation process using ObjectId, say <code>_id = new ObjectId.toString()</code>.</p>
  
  <p>I want to know if there is any side effects doing it this way? For example, will it impact the database performance or causing key conflicts in any means? Will it affect the sharding environment ...</p>