Error: "could not find implicit value for parameter readFileReader" trying to save a file using GridFS with reactivemongo - mongodb

Question

I am trying to save an attachment using reactivemongo in Play 2.1 using the following code:
def upload = Action(parse.multipartFormData) { request =>
request.body.file("carPicture").map { picture =>
val filename = picture.filename
val contentType = picture.contentType
val gridFS = new GridFS(db, "attachments")
val fileToSave = DefaultFileToSave(filename, contentType)
val futureResult: Future[ReadFile[BSONValue]] = gridFS.writeFromInputStream(fileToSave, new FileInputStream(new File(filename)))
Ok(Json.obj("e" -> 0))
}.getOrElse {
Redirect(routes.Application.index).flashing(
"error" -> "Missing file"
)
}
}
I am getting the following error:
could not find implicit value for parameter readFileReader: reactivemongo.bson.BSONDocumentReader[reactivemongo.api.gridfs.ReadFile[reactivemongo.bson.BSONValue]]
[error] val futureResult: Future[ReadFile[BSONValue]] = gridFS.writeFromInputStream(fileToSave, new FileInputStream(new File(filename)))
What am I missing?
Thanks,
GA

Answer 1

Most likely you don't have the DefaultReadFileReader implicit object in scope, which you can fix by adding an import:
import reactivemongo.api.gridfs.Implicits._
The following compiles fine for me (using the Play 2.1 reactivemongo module, version 0.9):
package controllers
import java.io.{ File, FileInputStream }
import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.Future
import play.api._
import play.api.mvc._
import play.api.libs.json._
import reactivemongo.api._
import reactivemongo.bson._
import reactivemongo.api.gridfs._
import reactivemongo.api.gridfs.Implicits._
import play.modules.reactivemongo.MongoController
object Application extends Controller with MongoController {
def index = Action {
Ok(views.html.index("Hello, world..."))
}
def upload = Action(parse.multipartFormData) { request =>
request.body.file("carPicture").map { picture =>
val filename = picture.filename
val contentType = picture.contentType
val gridFS = new GridFS(db, "attachments")
val fileToSave = DefaultFileToSave(filename, contentType)
val futureResult: Future[ReadFile[BSONValue]] = gridFS.writeFromInputStream(fileToSave, new FileInputStream(new File(filename)))
Ok(Json.obj("e" -> 0))
}.getOrElse {
Redirect(routes.Application.index).flashing(
"error" -> "Missing file"
)
}
}
}