Bdtjtk

Below is my simple document that represents a Link. I am using reactivemongo in scala for this.

I am getting this error during compilation:

app/components/Link.scala:60:11: No Json deserializer found for type
components.Link. Try to implement an implicit Reads or Format for this
type. [error] .one[Link]) [error] ^ [error] one error
found

I created the implicits in my Link companion object, which I also imported into my LinkRepo class.

Am I handling the mongo document _id correctly?

Should I use a String to map to the document ID, confused as to what is the best practise? Do I have to convert the String to the BSONObjectID at some point?

package components



import javax.inject.Inject

import reactivemongo.bson._



import reactivemongo.api.ReadPreference

import reactivemongo.api.collections.bson.BSONCollection

import reactivemongo.bson.{ BSONDocument, BSONObjectID }

import reactivemongo.api.commands.{ UpdateWriteResult, WriteResult, Upserted }

import reactivemongo.api.commands.bson.BSONUpdateCommand._

import reactivemongo.api.commands.bson.BSONUpdateCommandImplicits._



case class Link(id: Link.ID,

                name: String,

                url: String)





object Link {



  type ID = String



  implicit val linkReader: BSONDocumentReader[Link] =

    BSONDocumentReader[Link] { doc: BSONDocument =>

      Link(

        doc.getAs[String]("id").getOrElse(""),

        doc.getAs[String]("name").getOrElse(""),

        doc.getAs[String]("url").getOrElse(""))

    }



  implicit val linkWriter: BSONDocumentWriter[Link] =

    BSONDocumentWriter[Link] { link: Link =>

      BSONDocument(

        "id" -> link.id,

        "name" -> link.name,

        "url" -> link.url)

    }



}



import scala.concurrent.{ ExecutionContext, Future }

import reactivemongo.bson.{ BSONDocument, BSONObjectID }



import reactivemongo.api.{ Cursor, ReadPreference }

import reactivemongo.api.commands.WriteResult



import reactivemongo.play.json._

import reactivemongo.play.json.collection.JSONCollection



import play.modules.reactivemongo.ReactiveMongoApi



class LinkRepo @Inject()(implicit ec: ExecutionContext, reactiveMongoApi: ReactiveMongoApi) {

  import Link._



  def linksCol: Future[JSONCollection] = reactiveMongoApi.database.map(_.collection("links"))



  def byId(id: Link.ID): Future[Option[Link]] = {

    linksCol.flatMap(_.find(

      selector = BSONDocument("_id" -> id),

      projection = Option.empty[BSONDocument])

      .one[Link])

  }







}

My sbt has these lib versions:

scalaVersion := "2.12.7"



libraryDependencies += guice

libraryDependencies ++= Seq(

  guice,

  "joda-time" % "joda-time" % "2.9.9",

  "net.ruippeixotog" %% "scala-scraper" % "2.1.0",

  "org.reactivemongo"      %% "play2-reactivemongo" % "0.16.0-play26",

  "org.scalatestplus.play" %% "scalatestplus-play" % "3.1.2" % Test

)

plugins:

addSbtPlugin("com.typesafe.play" % "sbt-plugin" % "2.6.20")

As far as I know, you do not NEED TO use BSONObjectID, but it would be recommended.
But one thins you should use "_id" field in mongo, otherwise the default behaviour will be to create an _id on your document when you create a new one... so your document will have _id and id.

So you should get id from "_id" and write it into "_id" even if your case class is id.

As per handlers, for basic case classes you can use their provided macros:

implicit val linkHandler: BSONDocumentHandler[Link] = Macros.handler

this will generate the Reader and Writer for your Link.

When using the macros, you have an annotations that you can use to highlight your id will be "_id" on mongo:

import reactivemongo.bson.Macros.Annotations.Key



case class Link(

  @Key("_id")

  id: Link.ID,

  name: String,

  url: String

)