ReactiveMongo: How to use projection

json, mongodb, reactivemongo, scala

Solution

Here is the solution:

def find(selector: JsValue, projection: Option[JsValue]) = {
  var query = collection.genericQueryBuilder.query(selector)
  projection.map(query = query.projection(_))

  query.cursor[JsValue].collect[Vector](perPage).transform(
    success => success,
    failure => failure match {
      case e: LastError => DaoException(e.message, Some(DATABASE_ERROR))
    }
  )
}

or alternatively:

def find(selector: JsValue, projection: Option[JsValue]) = {
  val query = collection.genericQueryBuilder
    .query(selector)
    .projection(projection.getOrElse(Json.obj())

  query.cursor[JsValue].collect[Vector](perPage).transform(
    success => success,
    failure => failure match {
      case e: LastError => DaoException(e.message, Some(DATABASE_ERROR))
    }
  )
}

I hope that helps.

Problem

I'm trying to filter out the `password` field when querying a document from MongoDB with ReactiveMongo: ``` val projection = Json.obj("password" -> 0) def find(selector: JsValue, projection: Option[JsValue]) = { val query = collection.genericQueryBuilder.query(selector) projection.map(query.projection(_)) query.cursor[JsValue].collect[Vector](perPage).transform( success => success, failure => failure match { case e: LastError => DaoException(e.message, Some(DATABASE_ERROR)) } ) } ``` The code above has no effect... I also get the `password` field. If I try the following from the mongo client, then it works and `password` is not returned: ``` db.users.find( { username: 'j3d' }, { password:0} ) ``` Am I missing something?

Original source