scala – Akka-HTTP：文件上传

import akka.actor.ActorSystem
    import akka.event.{LoggingAdapter,Logging}
    import akka.http.scaladsl.Http
    import akka.http.scaladsl.model.{HttpResponse,HttpRequest}
    import akka.http.scaladsl.model.StatusCodes._
    import akka.http.scaladsl.server.Directives._
    import akka.stream.{ActorMaterializer,Materializer}
    import com.typesafe.config.Config
    import com.typesafe.config.ConfigFactory
    import scala.concurrent.{ExecutionContextExecutor,Future}
    import akka.http.scaladsl.model.StatusCodes
    import akka.http.scaladsl.model.HttpEntity
    import java.io._
    import akka.stream.io._

    object UploadTest extends App {
      implicit val system = ActorSystem()
      implicit val executor = system.dispatcher
      implicit val materializer = ActorMaterializer()

      val config = ConfigFactory.load()
      val logger = Logging(system,getClass)

      val routes = {
        pathSingleSlash {
          (post & extractRequest) { 
            request => {
              val source = request.entity.dataBytes
              val outFile = new File("/tmp/outfile.dat")
              val sink = SynchronousFileSink.create(outFile)
              source.to(sink).run()
              complete(HttpResponse(status = StatusCodes.OK))
            }
          }
        }
      }

      Http().bindAndHandle(routes,config.getString("http.interface"),config.getInt("http.port"))

    }

这段代码有几个问题：

>无法上载大于配置的实体大小的文件：
请求内容长度24090745超出配置的限制8388608
>连续执行两次上传会导致遇到死信.例外.

克服大小限制的最佳方法是什么？如何正确关闭文件,以便后续上传将覆盖现有文件(暂时忽略并发上载)？