No implicits found for parameter evidence$2: BodyWritable[Map[String, Object]]

Question

Working on play ws and have to prepare request param as {"initVideoUploadParams": {"videoMetadataParams":{"metadata":{"name":"","description":""}}}} . Tried the solution given in the link but didn't worked as my case is not similar to that question. Below is the code snippet

ws.url(savaUrl+configObj.get[String]("kaltura.init"))
                        .post(Map("initVideoUploadParams" -> InitVideoUploadParams(fileName,fileName)))

And the case class

case class InitVideoUploadParams(name:String,desc:String)

object InitVideoUploadParams {

  implicit object InitVideoUploadParamsWrites {
    def writes(name:String,desc:String): JsObject = Json.obj(
      "videoMetadataParams" -> VideoMetadataParams(Utils.createVideoParamsMap(name,desc)).metadata
    )   } }

case class VideoMetadataParams(metadata: Map[String, String])

object VideoMetadataParams {   implicit object VideoMetadataParamsWrites {
    def writes(metadata:Map[String,String]): JsObject = Json.obj(
      "metadata" -> metadata
    )   } }

Gone through the play documentation but not able to implement. Help me to understand what is wrong with my code.

Answer 1

You're trying to POST a value of type Map[String, InitVideoUploadParams] with Play-WS. In order for Play to know how to serialize that type to JSON, there needs to be an object of type Writes[InitVideoUploadParams] in the implicit scope. Apparently you were trying to do that with those implicit objects, but you need to extend Writes for that to work:

import play.api.libs.json.Writes
object InitVideoUploadParams {
  implicit object InitVideoUploadParamsWrites extends Writes[InitVideoUploadParams] {
    def writes(o: InitVideoUploadParams): JsValue = {
      ??? // implementation goes here
    }
  }
}

But it's a bit simpler to instead use the methods on the Writes companion object:

import play.api.libs.json.Writes
object InitVideoUploadParams {
  implicit val writes: Writes[InitVideoUploadParams] = Writes { o =>
    ??? //implementation goes here
  }
}