Example swapping a complete route tree

SwapRoutes.scala

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

class DynamicTree extends Directives {

  @volatile private var root: Route = reject

  private val apply = (requestContext: RequestContext) => root(requestContext)

  def dynamicRoot(initialRoute: Route): Route = {
    root = initialRoute.apply
    apply
  }

  def swapDynamic(newRoot: Route): Unit = {
    root = newRoot.apply
  }
}



object SwapRoutes extends App {
  implicit val system = ActorSystem()
  implicit val mat = ActorMaterializer()

  import Directives._

  val dynamicTree = new DynamicTree


  val alternative: Route = get {
    complete("alternative everything")
  }

  val route =
    dynamicTree.dynamicRoot(
      get {
        concat(
          path("swap") {
            dynamicTree.swapDynamic(alternative)
            complete("swapped behaviors")
          },
          // all other paths
          complete("initial tree")
        )
      }
    )

  Http().bindAndHandle(route, "127.0.0.1", 8080)

}