the description for this gist

post.scala

import akka.http.scaladsl.model.HttpMethods._
import akka.http.scaladsl.model.headers._
import akka.http.scaladsl.model.{ HttpResponse, StatusCodes }
import akka.http.scaladsl.server.Directives.{ complete, options, respondWithHeaders, _ }
import akka.http.scaladsl.server.{ Directive0, Route }

trait CORSHandler {

  private val corsResponseHeaders = List(
    `Access-Control-Allow-Origin`.*,
    `Access-Control-Allow-Credentials`(true),
    `Access-Control-Allow-Headers`("Authorization", "Content-Type", "X-Requested-With"))

  private def addAccessControlHeaders: Directive0 = {
    respondWithHeaders(corsResponseHeaders)
  }

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

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

  def addCORSHeaders(response: HttpResponse): HttpResponse =
    response.withHeaders(corsResponseHeaders)
}