How to send a file as a response using akka http?

问题

I am a little new to akka world, so my domain of knowledge is a bit small. I am creating an https server and handling it using akka streams and http, for a specific url, i need to send a file back to client. How can i achieve that using akka streams and avoiding the akka routes.

def handleCall(request:HttpRequest):HttpResponse = {
  logger.info("Request is {}",request)
  val uri:String = request.getUri().path()
  if(uri == "/download"){
    val f = new File("/1000.txt")
    logger.info("file download")
    return HttpEntity(
    //What should i put here if i want to return a text file.
    )
}

回答1:

If the file is likely to be large then you don't want to consume the entire contents into memory before sending it to the client. This is solved via a purely stream based solution:

import scala.io
import akka.stream.scaladsl.Source
import akka.http.scaladsl.model.HttpEntity.{Chunked, ChunkStreamPart}
import akka.http.scaladsl.model.{HttpResponse, ContentTypes}

val fileContentsSource : (String, String) => Source[ChunkStreamPart, _] =
  (fileName, enc) =>
    Source
      .fromIterator( io.Source.fromFile(fileName, enc).getLines )
      .map(ChunkStreamPart.apply)


val fileEntityResponse : (String, String) => HttpResponse =
  (fileName, enc) => 
    HttpResponse(entity = Chunked(ContentTypes.`text/plain(UTF-8)`,
                                  fileContentsSource(fileName, enc)))

Now you can create and send an HttpResponse without having the server keep the entire contents:

val httpResp : HttpResponse = fileEntityResponse("/foo/log.txt", "UTF8")

回答2:

val str2 = scala.io.Source.fromFile("/tmp/t.log", "UTF8").mkString
val str = Source.single(ByteString(str2))
HttpResponse(entity = HttpEntity.Chunked.fromData(ContentTypes.`application/octet-stream`, str))

回答3:

Akka Http Route

  pathSingleSlash {
    get {
      complete(HttpEntity.fromFile(ContentTypes.`application/octet-stream`, new File(s"/home/shivam/sample.zip"))
    }
  }

Curl Request

curl --output sample.zip http://localhost:8080/

Copied from HttpEntity.scala

 /**
   * Returns either the empty entity, if the given file is empty, or a [[HttpEntity.Default]] entity
   * consisting of a stream of [[akka.util.ByteString]] instances each containing `chunkSize` bytes
   * (except for the final ByteString, which simply contains the remaining bytes).
   *
   * If the given `chunkSize` is -1 the default chunk size is used.
   */

来源：https://stackoverflow.com/questions/49011621/how-to-send-a-file-as-a-response-using-akka-http

标签

scala

akka

akka-stream

akka-http