Akka HTTP API with CORS headers and custom Media types

AkkaHttpMicroService.scala

import akka.actor.ActorSystem
import akka.http.scaladsl.Http
import akka.stream.ActorMaterializer

object Boot extends App with Service with CorsSupport {
  override implicit val system = ActorSystem()
  override implicit val executor = system.dispatcher
  override implicit val materializer = ActorMaterializer()

  Http().bindAndHandle(corsHandler(routes), "0.0.0.0", 1337)
}

CorsHandler.scala

import akka.http.scaladsl.model.HttpMethods._
import akka.http.scaladsl.model.{StatusCodes, HttpResponse}
import akka.http.scaladsl.model.headers._
import akka.http.scaladsl.server.Directives._
import akka.http.scaladsl.server.{Directive0, Route}
import com.typesafe.config.ConfigFactory

trait CorsSupport {
  lazy val allowedOrigin = {
    val config = ConfigFactory.load()
    val sAllowedOrigin = config.getString("cors.allowed-origin")
    HttpOrigin(sAllowedOrigin)
  }

  //this directive adds access control headers to normal responses
  private def addAccessControlHeaders: Directive0 = {
    respondWithHeaders(
      `Access-Control-Allow-Origin`(allowedOrigin),
      `Access-Control-Allow-Credentials`(true),
      `Access-Control-Allow-Headers`("Authorization", "Content-Type", "X-Requested-With")
    )
  }

  //this handles preflight OPTIONS requests.
  private def preflightRequestHandler: Route = options {
    complete(HttpResponse(StatusCodes.OK).withHeaders(`Access-Control-Allow-Methods`(OPTIONS, POST, PUT, GET, DELETE)))
  }

  def corsHandler(r: Route) = addAccessControlHeaders {
    preflightRequestHandler ~ r
  }
}

dependencies.sbt

libraryDependencies ++= {
  val akkaV       = "2.3.12"
  val akkaStreamV = "1.0"
  Seq(
    "com.typesafe.akka" %% "akka-actor"                           % akkaV,
    "com.typesafe.akka" %% "akka-stream-experimental"             % akkaStreamV,
    "com.typesafe.akka" %% "akka-http-core-experimental"          % akkaStreamV,
    "com.typesafe.akka" %% "akka-http-experimental"               % akkaStreamV,
    "com.typesafe.akka" %% "akka-http-spray-json-experimental"    % akkaStreamV
  )
}

HttpService.scala

import akka.actor.ActorSystem
import akka.event.LoggingAdapter
import akka.http.scaladsl.marshallers.sprayjson.SprayJsonSupport._
import akka.http.scaladsl.marshalling.{ToEntityMarshaller, Marshaller}
import akka.http.scaladsl.model._
import akka.http.scaladsl.server.Directives._
import akka.stream.Materializer
import com.oxyme.monitoring.HealthChecker
import com.oxyme.monitoring.model.{Unhealthy, Healthy}
import com.typesafe.config.{ConfigFactory, Config}
import akka.http.scaladsl.model.StatusCodes._
import spray.json._
import spray.json.DefaultJsonProtocol

import scala.concurrent.ExecutionContextExecutor

case class Person(name: String, age: Int)
case class Persons(total: Int, data: Iterable[Person])

trait Protocols extends DefaultJsonProtocol {
  implicit val personFormat = jsonFormat2(Person.apply)
  implicit val personsFormat = jsonFormat2(Persons.apply)
  
  val `application/vnd.persons.v1+json` =
    MediaType.custom("application/vnd.persons.v1+json", MediaType.Encoding.Fixed(HttpCharsets.`UTF-8`))
    
  implicit val personsMarshaller: ToEntityMarshaller[Persons] = Marshaller.opaque { persons =>
    HttpEntity(ContentType(`application/vnd.persons.v1+json`, HttpCharsets.`UTF-8`), persons.toJson.compactPrint)
  }
}

trait Service extends Protocols {
  implicit val system: ActorSystem
  implicit val materializer: Materializer
  
  // declared here because it needs Materializer as opposed to Marshaller
  implicit val personsUnmarshaller = sprayJsonUnmarshaller[Persons].forContentTypes(
    `application/vnd.persons.v1+json`,
    `application/json`
  )
    
  val routes = {
    path("persons"){
      get {
        complete {
          Persons(3, Seq(Person("jeroen", 28), Person("harry", 12), Person("john", 31)))
        }
      }
    }
  }
}

There's also the respondWithHeaders directive which is slightly more straight-forward than mapResponseHeaders.

@jrudolph good point, thnx 👍

Good demo! It works well for me.

Perfect! Exactly what i was looking for.