title: Prevent Spring Data for Mongo to convert ids to ObjectId
body: <p>I'm using Spring Data for Mongo on an existing database. The previous application used plain strings for ids instead of ObjectId.</p>
  
  <p>My problem is that Spring Data insists on converting the strings to ObjectId, which makes all queries by id to fail.</p>
  
  <p>For example, when I do <code>repository.findOne('')</code>, the query executed is <code>{ "_id" : { "$oid" : "50cf9f34458cf91108ceb2b4"}}</code> when it should be <code>{ "_id" : "50cf9f34458cf91108ceb2b4" }</code></p>
  
  <p>Is there a way to avoid Spring Data to convert string ids to ObjectId?</p>
  
  <p>Thanks!</p>
  
  <p>Diego</p>