如何使用 akka http 发送文件作为响应？

Question

我对akka世界有点陌生，所以我的知识领域有点小。我正在创建一个 https 服务器并使用 akka 流和 http 处理它，对于特定的 url，我需要将文件发送回客户端。我如何使用 akka 流并避免使用 akka 路由来实现这一点。

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.
    )
}

Answer 1

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))

Answer 2

如果文件可能很大，那么您不希望在将其发送给客户端之前将全部内容消耗到内存中。这是通过纯基于流的解决方案解决的：

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)))

现在您可以创建并发送 HttpResponse 而无需服务器保留全部内容：

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

Answer 3

Akka Http 路由

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

Curl 请求

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

复制自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.
   */

如何使用 akka http 发送文件作为响应？

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

scala

akka

akka-stream

akka-http