Scala convert object to JSON response

Question

How can I convert the following case class object to JSON response, the case class contains multiple nested object value.

I got exception when I use jsonFormat5(responseData)

val simpleBanner1 = Banner(112, "http://dummyimage.com/300x250", 300, 250)
val responseData = BidResponse(uuid, "XN2zZQABxJsKK0jU4QnIzw", campaignData.bid, Option("4548"), Option(simpleBanner1))

Exception

Error:(63, 47) could not find implicit value for evidence parameter of type bidder.RestService.JF[Option[bidder.Banner]]
implicit val bidResponseFormat = jsonFormat5(BidResponse)

Error:(63, 47) not enough arguments for method jsonFormat5: (implicit evidence$25: bidder.RestService.JF[String], implicit evidence$26: bidder.RestService.JF[String], implicit evidence$27: bidder.RestService.JF[Double], implicit evidence$28: bidder.RestService.JF[Option[String]], implicit evidence$29: bidder.RestService.JF[Option[bidder.Banner]], implicit evidence$30: scala.reflect.ClassTag[bidder.BidResponse])spray.json.RootJsonFormat[bidder.BidResponse].
Unspecified value parameters evidence$29, evidence$30.
implicit val bidResponseFormat = jsonFormat5(BidResponse)

Error:(76, 28) Cannot find JsonWriter or JsonFormat type class for bidder.BidResponse
          responseData.toJson
Error:(76, 28) not enough arguments for method toJson: (implicit writer: spray.json.JsonWriter[bidder.BidResponse])spray.json.JsValue.
Unspecified value parameter writer.
          responseData.toJson

emran · Accepted Answer · 2019-05-20 17:22:45Z

1

jsonFormat5 should be used with the case class, as it defines how to the object should be encoded. Your code should look like this:

import spray.json._
import DefaultJsonProtocol._

// define format implicitly for BidResponse and Banner case classes
implicit val bannerFormat = jsonFormat4(Banner)
implicit val bidResponseFormat = jsonFormat5(BidResponse)

// serialize BidResponse object
val bidResponseJson = responseData.toJson

Here is an extended example:

import spray.json._
import DefaultJsonProtocol._

// example case classes
case class Banner(num: Int, url: String, num2: Int, num3: Int)
case class BidResponse(uuid: String, code: String, num: Int, opt: Option[String], banner: Option[Banner])

implicit val bformat = jsonFormat4(Banner)
implicit val format = jsonFormat5(BidResponse)

val simpleBanner1 = Banner(112, "http://dummyimage.com/300x250", 300, 250)
val responseData = BidResponse("abcdef", "XN2zZQABxJsKK0jU4QnIzw", 1234, Option("4548"), Option(simpleBanner1))

println( responseData.toJson )

As mentioned in the comments, the Banner format must be defined implicitly because the BidResponse object depends on it. ref: bformat variable.

edited May 20, 2019 at 17:22

answered May 20, 2019 at 11:02

emran

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8 Comments

Abdul Awal Over a year ago

Hi @terminally-chill, I already tried it before, got exception

Error:(63, 47) could not find implicit value for evidence parameter of type bidder.RestService.JF[Option[bidder.Banner]]   implicit val bidResponseFormat = jsonFormat5(BidResponse)

Abdul Awal Over a year ago

Error:(63, 47) not enough arguments for method jsonFormat5: (implicit evidence$25: bidder.RestService.JF[String], implicit evidence$26: bidder.RestService.JF[String], implicit evidence$27: bidder.RestService.JF[Double], implicit evidence$28: bidder.RestService.JF[Option[String]], implicit evidence$29: bidder.RestService.JF[Option[bidder.Banner]], implicit evidence$30: scala.reflect.ClassTag[bidder.BidResponse])spray.json.RootJsonFormat[bidder.BidResponse]. Unspecified value parameters evidence$29, evidence$30.   implicit val bidResponseFormat = jsonFormat5(BidResponse)

emran Over a year ago

@AbdulAwal you should add Banner as an implicit val as well. Updated the answer showing both in scope.

Abdul Awal Over a year ago

I update it as implicit val simpleBanner1 = Banner(112, "http://dummyimage.com/300x250", 300, 250) but the error remain the same

emran Over a year ago

@AbdulAwal Can you include the case class definitions? I can re-create this exception when using the wrong jsonFormat function. Are there any default values in the case class definition?

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