MultiPart File Upload with Quarkus / Kotlin - kotlin

Question

I am trying to build a multi-part file upload REST route in Quarkus (using Kotlin), but having issues with the route mapping.
From the Client side I am posting a form that contains a text value and a file value.
const formData = new FormData();
formData.append("text", text);
formData.append("file", files[0]);
fetch('http://localhost:8080/data', {
method: 'POST',
body: formData
})
From the serverside, I am trying to retrieve the values as follows.
class FormData(#FormParam("text") #PartType(MediaType.TEXT_PLAIN) var text:String,
#FormParam("file") #PartType(MediaType.APPLICATION_OCTET_STREAM) var file:InputStream)
#Path("/data")
class FormUploadResource {
#POST
#Consumes(MediaType.MULTIPART_FORM_DATA)
fun upload(#MultipartForm form:FormData) {
println(form.text)
println(form.file)
}
}
However, when I execute the endpoint, I get a org.jboss.resteasy.spi.ReaderException: java.lang.NoSuchMethodException: error.
I have tried to make sure that the text and file parameters are correctly being received, and have inspected the payload coming in with the following code
#POST
#Consumes(MediaType.MULTIPART_FORM_DATA)
fun upload(input:MultipartFormDataInput) {
var map = input.getFormDataMap()
map.entries.forEach {
println("""${it.key} - ${it.value}""")
if (it.value is List<InputPart>) {
it.value.forEach { ip ->
println(""" --- ${ip.getMediaType()} """ )
}
}
}
}
And it correctly says
text - [org.jboss.resteasy.plugins.providers.multipart.MultipartInputImpl$PartImpl#660c4317]
--- text/plain;charset=UTF-8
file - [org.jboss.resteasy.plugins.providers.multipart.MultipartInputImpl$PartImpl#3aee346]
--- application/octet-stream;charset=UTF-8
I assume there is something going wrong with the FormData class that RestEasy isn't automagically mapping to it. I have tried changing the type for "file" to be ByteArray and File, and they both fail also.
I have struggled to find Kotlin specific answers, so it is possible this is a Kotlin oddity also.

Answer 1

I just went through this issue, showing no logs at all. I managed to make it work, it seems that a empty constructor is required :
class FormData() {
#FormParam("text") #PartType(MediaType.TEXT_PLAIN)
var text: String? = null
#FormParam("file") #PartType(MediaType.APPLICATION_OCTET_STREAM)
var file: InputStream? = null
}
However I must still be missing something because
class FormData(
#FormParam("text") #PartType(MediaType.TEXT_PLAIN) var text: String?,
#FormParam("file") #PartType(MediaType.APPLICATION_OCTET_STREAM) var file: InputStream?
) {
constructor() : this(null, null)
}
enters in the method but doesn't init values
Edit: after testing secondary constructors and primary constructors like this working one,
class FormData
{
#FormParam("file")
#PartType(MediaType.APPLICATION_OCTET_STREAM)
var file: InputStream? = null
constructor() {
this.file = null
}
}
It seems that an EMPTY PRIMARY CONSTRUCTOR is required :)
Hope it helped !

Answer 2

I won't mark this answer as correct, as I am not happy with the solution, but it at least works.
#POST
#Consumes(MediaType.MULTIPART_FORM_DATA)
fun upload(input:MultipartFormDataInput) {
val map = input.getFormDataMap()
val text = map.get("text")?.first()?.getBodyAsString() ?: ""
val file = map.get("file")?.first()?.getBodyAsString() ?: ""
println(form.text)
println(form.file)
}
As you can see, I am getting the data directly from the MultipartFormDataInput, rather than auto-constructing the object. Hopefully someone is able to shed some light on why this work around is needed, or whether a better solution is available.