File upload using akka-http in Scala

January 23, 2016September 10, 2018 Rishi KhandelwalAkka, Future, Studio-Scala13 Comments

Table of contents

Reading Time: 2 minutes

Lets begin with some introduction of Akka-http first.

Akka HTTP is a layer to expose Actors to the web via HTTP and to enable them to consume HTTP services as a client. It is not an HTTP framework, it is an Actor-based toolkit for interacting with web services and clients. This toolkit is structured into several layers:

akka-http-core: A complete implementation of the HTTP standard, both as client and server.
akka-http: A convenient and powerful routing DSL for expressing web services.
akka-http-testkit: A test harness and set of utilities for verifying your web service implementations.

For more information, see here.

Now its time to go into some code.

To use akka-http, we need to add library in our application. So to do the same, add following dependencies in build.sbt file.:


"com.typesafe.akka" %% "akka-stream-experimental" % "2.0.2",
"com.typesafe.akka" %% "akka-http-core-experimental" % "2.0.2",
"com.typesafe.akka" %% "akka-http-experimental" % "2.0.2"

Now we will write a route to which we can send our file upload request :


package com.rishi

import java.io.FileOutputStream
import java.util.UUID

import akka.actor.ActorSystem
import akka.http.scaladsl.model.{HttpResponse, Multipart, StatusCodes}
import akka.http.scaladsl.server.Directives._
import akka.http.scaladsl.server.Route
import akka.stream.ActorMaterializer
import akka.util.ByteString

trait FileUpload {

implicit val system = ActorSystem()
implicit val executor = system.dispatcher
implicit val materializer = ActorMaterializer()

/**
* Route for uploading file
*/
def uploadFile: Route = {
path("user" / "upload" / "file") {
(post & entity(as[Multipart.FormData])) { fileData =>
complete {
val fileName = UUID.randomUUID().toString
val temp = System.getProperty("java.io.tmpdir")
val filePath = temp + "/" + fileName
processFile(filePath,fileData).map { fileSize =>
HttpResponse(StatusCodes.OK, entity = s"File successfully uploaded. Fil size is $fileSize")
}.recover {
case ex: Exception => HttpResponse(StatusCodes.InternalServerError, entity = "Error in file uploading")
}
}
}
}
}

private def processFile(filePath: String, fileData: Multipart.FormData) = {
val fileOutput = new FileOutputStream(filePath)
fileData.parts.mapAsync(1) { bodyPart ⇒
def writeFileOnLocal(array: Array[Byte], byteString: ByteString): Array[Byte] = {
val byteArray: Array[Byte] = byteString.toArray
fileOutput.write(byteArray)
array ++ byteArray
}
bodyPart.entity.dataBytes.runFold(Array[Byte]())(writeFileOnLocal)
}.runFold(0)(_ + _.length)
}

val routes = uploadFile
}

Here, what we have done is, as route will get file upload request, it will take the file data as multipart and will create a file at our local machine in system’s temp folder.

That’s it. Hope you enjoyed. Happy Blogging. !!!

Written by Rishi Khandelwal

Rishi is a tech enthusiast with having around 10 years of experience who loves to solve complex problems with pure quality. He is a functional programmer and loves to learn new trending technologies. His leadership skill is well prooven and has delivered multiple distributed applications with high scalability and availability by keeping the Reactive principles in mind. He is well versed with Scala, Akka, Akka HTTP, Akka Streams, Java8, Reactive principles, Microservice architecture, Async programming, functional programming, distributed systems, AWS, docker.

13 thoughts on “File upload using akka-http in Scala2 min read”

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Anand Krishnan says:

January 26, 2016 at 11:29 PM

Hi, I am getting an error in the function processFile() – not enough arguments for method runFold: (implicit materializer: akka.stream.Materializer)scala.concurrent.Future[Array[Byte]]. Unspecified value parameter materializer. I tried adding these:

import akka.actor.ActorSystem
import akka.stream.ActorMaterializer
implicit val system = ActorSystem(“Sys”)
implicit val materializer = ActorMaterializer()

Then I started getting error in the uploadFile function in line : processFile(filePath, fileData).map { fileSize =>

◾Cannot find an implicit ExecutionContext. You might pass an (implicit ec: ExecutionContext) parameter to your method or import scala.concurrent.ExecutionContext.Implicits.global

Can you pls help me resolve this, so that the async nature is not lost
1. Rishi Khandelwal says:
  
  January 27, 2016 at 12:30 PM
  
  Hi Anand. Thanks for pointing me the error.
  
  I have updated the blog. I missed to include some implicit variables.
  Now please give it a try one more time and let me know if you get any error.
A.G. says:

January 27, 2016 at 4:38 PM

Hello Rishi,
Is there a specific reason you did not use standard fileUpload akka-http directive? http://doc.akka.io/docs/akka-stream-and-http-experimental/2.0.2/scala/http/routing-dsl/directives/file-upload-directives/fileUpload.html#fileupload
1. Anand Krishnan says:
  
  February 3, 2016 at 8:00 AM
  
  Thanks for this information
2. Rishi Khandelwal says:
  
  March 11, 2016 at 4:49 PM
  
  Sorry for late reply. I was away for some reason.
  Actually initially i tried file upload with version 1.0 and fileUpload directive was not there in this version. In later version, this directive has included.
  
  And, thanks for the information. This fileUpload directive is really a good option.
Anand Krishnan says:

February 3, 2016 at 8:02 AM

Hello Rishi,
One other thing I noticed is that, when I try to upload a file of size 150 MB, the POST request is failing after around 8-9 seconds. Any idea how to fix it?
A.G. says:

February 3, 2016 at 4:57 PM

Hello Anand,
150MB issue may be related to akka-http config. Default incoming request size is 8MB. Have you tried increasing akka.http.server.parsing.max-content-length ?
http://doc.akka.io/docs/akka-stream-and-http-experimental/2.0.2/scala/http/configuration.html
Rishi Khandelwal says:

March 30, 2016 at 12:20 PM

Reblogged this on Rishi Khandelwal.
avis says:

May 17, 2016 at 2:40 PM

Looks good, How do we get form-data inside multipart?
1. Rishi Khandelwal says:
  
  June 1, 2016 at 5:38 PM
  
  Hi avis,
  
  Please find below link for your query :
  https://blog.knoldus.com/2016/06/01/a-basic-application-to-handle-multipart-form-data-using-akka-http-with-test-cases-in-scala/
Pingback: Test cases for file upload using akka-http in Scala | Knoldus
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