akka-http, response with "application/json" media type

[dmitry....@iohk.io]

Hi!

I have a simple route, that should respond (as I expect) with `application/json` media type. 

 def height: Route = {
   path("height") {
     // respondWithHeaders(`Content-Type`(MediaTypes.`application/json`))(complete("???")) // also don't work
     respondWithHeaders(RawHeader("Content-Type", "application/json"))(complete("???"))
   }
 }

But when I do requests to this route, I see Content-Type: text/plain :

 $ curl -X GET -v 'http://localhost:9085/blocks/height'
* Hostname was NOT found in DNS cache
*   Trying 127.0.0.1...
* Connected to localhost (127.0.0.1) port 9085 (#0)
> GET /blocks/height HTTP/1.1
> User-Agent: curl/7.35.0
> Host: localhost:9085
> Accept: */*
> 
< HTTP/1.1 200 OK
* Server akka-http/2.4.4 is not blacklisted
< Server: akka-http/2.4.4
< Date: Fri, 22 Apr 2016 14:04:18 GMT
< Content-Type: text/plain; charset=UTF-8
< Content-Length: 3
< 
* Connection #0 to host localhost left intact
???


What should I change to get `application/json` media typ&

[Konrad Malawski]

Content-Type is special – it should come with/from the data you're completing with – please don't hardcode it like that (it won't work, and that's on purpose).

Here's how you'd use JSON in a real world app:

object TestServer extends App
  with SprayJsonSupport with DefaultJsonProtocol {

  implicit val system = ActorSystem()
  implicit val materializer = ActorMaterializer()
  import system.dispatcher

  import Directives._

  final case class Thingy(value: String)
  implicit val thingyFormat = jsonFormat1(Thingy)

  val routes =
    complete(Thingy(""))

  val bindingFuture = Http().bindAndHandle(routes, interface = "localhost", port = 8080)

  println(s"Server online at http://localhost:8080/\nPress RETURN to stop...")
  Console.readLine()

  bindingFuture.flatMap(_.unbind()).onComplete(_ ⇒ system.terminate())

}

Please read up about JSON Support: http://doc.akka.io/docs/akka/2.4.4/scala/http/common/json-support.html#akka-http-spray-json

If you really want to do raw hardcoding of content type header, you can by returning HttpEntity:

val routes =
  complete(HttpEntity(ContentTypes.`application/json`, "{}"))

$ http localhost:8080  Accept:*/*

HTTP/1.1 200 OK

Content-Length: 2

Content-Type: application/json

Date: Fri, 22 Apr 2016 14:24:19 GMT

Server: akka-http/2.4-SNAPSHOT

{}

Happy hakking!

-- 
Konrad `ktoso` Malawski
Akka @ Lightbend

On 22 April 2016 at 16:19:27, dmitry....@iohk.io (dmitry....@iohk.io) wrote:

Hi!

I have a simple route, that should respond (as I expect) with `application/json` media type. 

 def height: Route = {
   path("height") {
     // respondWithHeaders(`Content-Type`(MediaTypes.`application/json`))(complete("???")) // also don't work
     respondWithHeaders(RawHeader("Content-Type", "application/json"))(complete("???"))
   }
 }


But when I do requests to this route, I see Content-Type: text/plain :

What should I change to get `application/json` media typ&

 $ curl -X GET -v 'http://localhost:9085/blocks/height'
* Hostname was NOT found in DNS cache
*   Trying 127.0.0.1...
* Connected to localhost (127.0.0.1) port 9085 (#0)
> GET /blocks/height HTTP/1.1
> User-Agent: curl/7.35.0
> Host: localhost:9085
> Accept: */*
>
< HTTP/1.1 200 OK
* Server akka-http/2.4.4 is not blacklisted
< Server: akka-http/2.4.4
< Date: Fri, 22 Apr 2016 14:04:18 GMT
< Content-Type: text/plain; charset=UTF-8
< Content-Length: 3
<
* Connection #0 to host localhost left intact
???


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[dmitry....@iohk.io]

Thanks for your response!

Is it possible to combine it with play-json?

My spray function I'm trying to rewrite looks like 

 def jsonRoute(fn: => ToResponseMarshallable, method: Directive0 = get): Route = method {
    val jsonResponse = respondWithMediaType(`application/json`) {
      complete(fn)
    }
    if (corsAllowed) respondWithHeader(RawHeader("Access-Control-Allow-Origin", "*"))(jsonResponse)
    else jsonResponse
  }

I still can't see how to combine your response (even the `hacking` one) with ToResponseMarshallable..