How to call a POST to another service and receive json data - scala

Question

I have two Akka HTTP services (Service 1 and Service 2). One needs to communicate with the other.
Service 2 provides a POST endpoint /lastname that takes in json payload like this {name: "doe"} and returns {"returnVal":false} or {"returnVal":true}
Question
How can Service 1 connect to it, send json payload, and fetch the boolean response?
I am trying below:
val responseFuture: Future[HttpResponse] = Http().singleRequest(
HttpRequest(
uri = s"$host:$port/my/endpoint")
entity = HttpEntity(MediaTypes.`application/json`, method = HttpMethods.POST)
)
but I can't figure out out to send json data {name: "doe"} along with the request.

Answer 1

for creating JSON you need to use json marshaller like upickle, spray-json. I use spray json for converting scala classes to json and vice versa. I assume Service2 take {"name": "paul"} as request and return {"exist": true} as response.
import spray.json.{DefaultJsonProtocol, RootJsonFormat}
case class NameExistsRequest(name: String)
case class NameExistsResponse(exist: Boolean)
object ServiceJsonProtocolNameExists extends DefaultJsonProtocol{
implicit val nameExistsRequestJF: RootJsonFormat[NameExistsRequest] = jsonFormat1(NameExistsRequest)
implicit val nameExistsResponseJF: RootJsonFormat[NameExistsResponse] = jsonFormat1(NameExistsResponse)
}
case object NameExistsError extends RuntimeException with NoStackTrace
case object InternalError extends RuntimeException with NoStackTrace
def sendNameExistsRequest(): Future[NameExistsResponse] = {
import ServiceJsonProtocolNameExists._
import spray.json._
val endpoint = "http://your-endpoint"
val request = NameExistsRequest("paul")
val httpRequest = HttpRequest(
method = HttpMethods.POST,
uri = Uri(endpoint),
headers = List.empty,
entity = HttpEntity(ContentTypes.`application/json`, request.toJson.toString)
)
Http().singleRequest(httpRequest).transformWith {
case Success(response) =>
response match {
case HttpResponse(StatusCodes.OK, _, entity, _) =>
Unmarshal(entity).to[String].map {content =>
content.parseJson.convertTo[NameExistsResponse]
}
case res =>
println("failure response: " + res)
Future.failed(NameExistsError)
}
case Failure(f) =>
println("failed to send request, caused by: " + f)
Future.failed(InternalError)
}
}
which NameExistsRequest represent your request and we convert it to json with toJson method and NameExistsResponse represent your response which returned by Service2. we use Unmarshall and convertTo, to convert json to scala class.