How to convert casbah mongodb list to json in scal

Question

I'm learning scala and mongodb at present and using the play! framework, so I'm making all sorts of mistakes as I get my head around things. Currently I have a scala object that returns a list of database objects returned from a mongodb query via casbah as follows;

object Alerts  {

   def list() : List[DBObject]= {

        val collection = MongoDatabase.collection;
        val query = MongoDBObject.empty
        val order = MongoDBObject("Issue Time:" -> -1)
        val list = collection.find(query).sort(order).toList
        list
   }

... }

Elsewhere in my code I wish to output the List of objects in Json - so I have;

  val currentAlerts = Alerts.list()

What I'd like to write is something like;

  val resultingJson = currentAlerts.toJson 

But when I do this, I understandably get the following error;

  value toJson is not a member of List[com.mongodb.casbah.Imports.DBObject]

My question is - what's the right way to convert a List of com.mongodb.casbah.Imports.DBObject into Json for output?

EDIT:

For clarity, what I really want to do is the equivalent of

val listInJson = collection.find(query).sort(order).toJson

In the same way that I CAN write

val listAsString = collection.find(query).sort(order).toString

Answer 1

You can try

com.mongodb.util.JSON.serialize(Alerts.list())

This should return a JSON array with your Alerts

Answer 2

I have the following

def service() = Action {
 // connect
 val collection = MongoConnection()("someDB")("someCollection")
 // simply convert the result to a string, separating items with a comma
 // this string goes inside an "array", and it's ready to hit the road
 val json = "[%s]".format(
  collection.find(someQuery).toList.mkString(",")
 )

 Ok(json).as("application/json")

}

Answer 3

I have what is a horrid solution as follows;

val currentAlerts = Alerts.list()

var jsonList : List[JsValue] = Nil

// Iterate over the DBObjects and use to String to convert each to JSON
// and then parse that back into the list so we can use toJson on it later.
// MAD, but works.

for (dbObject <- currentAlerts) {
    jsonList ::=  Json.parse(dbObject.toString)
}

val result = Json.toJson(jsonList)
Ok(result).as("application/json")

There must surely be a better way?