How to use ReactiveMongo + JSON aggregation framework in Play Framework?

Question

I need to utilize MongoDB's aggregation framework using ReactiveMongo. I only find this example which uses BSON. I would like to use JSON so I changed the code to :

def populatedStates(col: JSONCollection) = {
  import col.BatchCommands.AggregationFramework.{AggregationResult, Group, Match, SumField}
  val res: Future[AggregationResult] = col.aggregate(
    Group(JsString("$state"))("totalPop" -> SumField("population")),
    List(Match(JSONDocument("totalPop" -> JSONDocument("$gte" -> 10000000L)))))
  res.map(_.firstBatch)
}

But there's no "JSONDocument" type.

What would be the correct way to finish this approach?

score 4 · Accepted Answer · answered Mar 23 '16 at 05:28

4

JSONDocument is the same as JsObject when you use JSONSerializationPack. JsObject converts to JSONDocument with implicit writer.

import play.api.libs.json._
import reactivemongo.play.json._
import reactivemongo.play.json.collection.JSONCollection

import scala.concurrent.Future

def populatedStates(col: JSONCollection) = {
  import col.BatchCommands.AggregationFramework.{AggregationResult, Group, Match, SumField}
  val res: Future[AggregationResult] = col.aggregate(
    Group(JsString("$state"))("totalPop" -> SumField("population")),
    List(Match(Json.obj("totalPop" -> Json.obj("$gte" -> 10000000L)))))
  res.map(_.firstBatch)
}

answered Mar 23 '16 at 05:28

andrey.ladniy

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This is what I did, but I 've got an error message. I've asked a new question with my own code here: http://stackoverflow.com/questions/36184408/get-an-error-message-while-tring-to-rewrite-reactivemongo-bson-to-json-in-play – Roger Chien Mar 23 '16 at 17:04
Thanks a lot! Couldn't find a solution anywhere else :) – phidias Aug 23 '16 at 14:57

score 1 · Answer 2 · edited Aug 01 '17 at 01:03

For example you want execute example from https://docs.mongodb.com/v3.4/reference/operator/aggregation/subtract/#subtract-numbers with 'total' sorting Using play reacitve mongo 0.12.0 it should look as

// don't forget to import this !!
import reactivemongo.play.json.commands.JSONAggregationFramework._

def salesDb = reactiveMongoApi.database.map(_.collection[JSONcollection]("sales"))

val result = salesDb.flatMap { collection =>
  val projectOperator = Project(
    Json.obj(
        "item" -> 1,
        "total" -> Json.obj("$subtract" -> JsArray(Seq(Json.obj("$add" -> Seq("$price", "$fee")), JsString("$discount"))))
    )
  )
  val sortOperator = Sort(Ascending("total"))
  collection.aggregate(firstOperator = projectOperator, otherOperators = List(sortOperator)).map { agregationResult =>
    agregationResult.firstBatch
  }
}

How to use ReactiveMongo + JSON aggregation framework in Play Framework?

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