title: MongoDB - Error: field names cannot start with $ [$oid]
body: <p>I'm facing an issue while trying to import .json files that were exported using the mongoexport command.
  The generated .json files contains the character $ in some variables such as $oid and $numberLong().</p>
  
  <pre><code>{"_id":{"$oid":"55aff0e7b3bdf92b314b6fa6"},"activated":true,"authRole":"USER","authToken":"5bdad308-4a11-4890-8c3e-82c29530f1bc","birthDate":{"$date":"2015-08-06T03:00:00.000Z"},"comercialPhone":"99999994","email":"test@mail.com","mobilePhone":"99999999","name":"Test Test","password":"$2a$10$y","validationToken":"b2cd0d71-cb47-405d-bf7f-e46e1a8706e4","version":{"$numberLong":"35"}}
  </code></pre>
  
  <p>However, this format is not acceptable while importing the files. This format seems to be the strict mode, but I'd like to generate json files using the shell format which shows $oid as ObjectId.</p>
  
  <p>Is there any workaround for this?</p>
  
  <p>Thanks!</p>