Akka HTTP 1.0 CORS Support

AkkaHttpCorsSupport.scala

import akka.http.scaladsl.model.HttpHeader
import akka.http.scaladsl.model.HttpMethods._
import akka.http.scaladsl.model.HttpResponse
import akka.http.scaladsl.model.headers.`Access-Control-Allow-Credentials`
import akka.http.scaladsl.model.headers.`Access-Control-Allow-Methods`
import akka.http.scaladsl.model.headers.`Access-Control-Allow-Origin`
import akka.http.scaladsl.model.headers.Origin
import akka.http.scaladsl.server.Directive0
import akka.http.scaladsl.server.Directives._
import akka.http.scaladsl.server.MethodRejection
import akka.http.scaladsl.server.RejectionHandler

trait CorsSupport {

  protected def corsAllowOrigins: List[String]

  protected def corsAllowedHeaders: List[String]

  protected def corsAllowCredentials: Boolean

  protected def optionsCorsHeaders: List[HttpHeader]

  protected def corsRejectionHandler(allowOrigin: `Access-Control-Allow-Origin`) = RejectionHandler
    .newBuilder().handle {
      case MethodRejection(supported) =>
        complete(HttpResponse().withHeaders(
          `Access-Control-Allow-Methods`(OPTIONS, supported) ::
            allowOrigin ::
            optionsCorsHeaders
        ))
    }
    .result()

  private def originToAllowOrigin(origin: Origin): Option[`Access-Control-Allow-Origin`] =
    if (corsAllowOrigins.contains("*") || corsAllowOrigins.contains(origin.value))
      origin.origins.headOption.map(`Access-Control-Allow-Origin`.apply)
    else
      None

  def cors[T]: Directive0 = mapInnerRoute { route => context =>
    ((context.request.method, context.request.header[Origin].flatMap(originToAllowOrigin)) match {
      case (OPTIONS, Some(allowOrigin)) =>
        handleRejections(corsRejectionHandler(allowOrigin)) {
          respondWithHeaders(allowOrigin, `Access-Control-Allow-Credentials`(corsAllowCredentials)) {
            route
          }
        }
      case (_, Some(allowOrigin)) =>
        respondWithHeaders(allowOrigin, `Access-Control-Allow-Credentials`(corsAllowCredentials)) {
          route
        }
      case (_, _) =>
        route
    })(context)
  }
}

Main.scala

...

object Main extends App with CorsSupport {
  override val corsAllowOrigins: List[String] = List("*")

  override val corsAllowedHeaders: List[String] = List("Origin", "X-Requested-With", "Content-Type", "Accept", "Accept-Encoding", "Accept-Language", "Host", "Referer", "User-Agent")

  override val corsAllowCredentials: Boolean = true

  override val optionsCorsHeaders: List[HttpHeader] = List[HttpHeader](
    `Access-Control-Allow-Headers`(corsAllowedHeaders.mkString(", ")),
    `Access-Control-Max-Age`(60 * 60 * 24 * 20), // cache pre-flight response for 20 days
    `Access-Control-Allow-Credentials`(corsAllowCredentials)
  )
  
  val routes = cors {
    complete("CORS YES!")
  }
  ...
}