title: Spring data mongodb update custom field
body: <p>I have an <strong><em>_id</em></strong> of mongodb object and want to update only a specific field in DB. Is there a way not to get the entire object with <strong><em>findone(id)</em></strong> then set required field and <strong><em>save</em></strong> to mongodb again? I want something like <strong><em>sql update</em></strong> mechanism which  didn't find in mongodb yet. 
  I use java Spring data.</p>