Create and stream a zip file as it is beeing created with the playframework and scala

Question

My scala-play api provides endpoints to return a file as a stream via the Ok.chunked-function.

I now want to be able to allow the download of multiple files as a zip archive.

I want to create a zip file as a stream which play should directly return as a filestream. Meaning without the need to temporarly save the zip-file on the disc and serving it while it is being created.

What would be a good way to implemente a function that creates this stream?

Answer 1

I solved the issue by using akkas alpakka.

import akka.stream.alpakka.file.ArchiveMetadata
import akka.stream.alpakka.file.scaladsl.Archive
import akka.stream.scaladsl.Source
import akka.util.ByteString

val fileSource: Source[ByteString, _]  = FileIO.fromPath(path)
val tupelWithMetaData = (ArchiveMetadata(s"file.txt"), fileSource)

val stream: Source[ByteString, _] = Source(List(tupelWithMetaData)).via(Archive.zip())

First I create a akka ByteString source. The source is used inside the Tupel2 with some ArchiveMetadata. This tuple can than be used to create a new source which can be connected to alpakkas Archive.zip().

The resulting stream can than be used with plays Ok.chunked.

I hope this solution might help you if you have the same question.