Upload File 🔗

Submit the form as multipart/form-data and parse the upload as a NIO Path. The server adapter must support multipart forms; see the parsing reference.

// 1. somewhere in a view, use enctype="multipart/form-data"
html"""
    <form action="/form-submit" method="POST" enctype="multipart/form-data">
    ...
    </form>
"""

// 2. define form data class with a NIO Path file
import java.nio.file.{Files, Path as FilePath}
import ba.sake.formson.*

case class MyData(file: FilePath) derives FormDataRW

// 3. handle the file however you want
case POST -> Path("form-submit") =>
  val formData = Request.current.bodyForm[MyData]
  val fileAsString = Files.readString(formData.file)

You can find a working example in the repo.

Read or copy the upload while handling the request. The temporary file is owned by the adapter and deleted automatically, including on parsing and handler failures. Potateh deletes uploads before deferred response writing, so copy an upload first if the response or background work needs it later.

To keep an upload, copy it into application-owned storage before returning:

val formData = Request.current.bodyForm[MyData]
val destination = Files.createTempFile(applicationUploadDirectory, "upload-", ".bin")
Files.copy(formData.file, destination, java.nio.file.StandardCopyOption.REPLACE_EXISTING)

Choose applicationUploadDirectory in your application configuration. Do not use a client-supplied filename as a storage path. The shared parser always creates files on disk, including empty uploads; its limits and Undertow's separate upload behavior are listed in the parsing reference.