I’ve got an endpoint that returns valid JSON with ...

# ktor

[Matti MK]

I’ve got an endpoint that returns valid JSON with Content-Type text/html; charset=UTF-8. The response is as follows { "result": [ "foo", "bar" ] }. When I try to serialize this into a POJO Ktor I get the following error:

No transformation found: class io.ktor.utils.io.ByteBufferChannel -> class FooList

This is most certainly about the wrong Content-Type, as with valid application/json header everything works as expected. Unfortunately, I cannot change the server’s headers.

Is there a workaround for this on client side? I tried with accept(ContentType.Text.Plain) as well as accept(ContentType.Any) but those don’t really help.

[Matti MK]

With search I can find some workarounds for this, such as manually serializing the response. I’d like to avoid this, if possible 😄

[Matti MK]

In case someone stumbles upon this and wonders about the manual decoding:

Json.decodeFromString<FooClass>(response.body())

[Rustam Siniukov]

you can register any Content-Type header value with ContentNegotiation plugin

install(ContentNegotiation) {
  register(ContentType.Text.Plain, KotlinxSerializationConverter(Json))
}

[Matti MK]

Thanks!

Which Ktor/ContentNegotiation/Serialization version would this be?

I can’t see Json as a `SerialFormat`:

https://kotlinlang.org/api/kotlinx.serialization/kotlinx-serialization-core/kotlinx.serialization/-serial-format/

[Matti MK]

Righty, after some Googling I ended up with this block inside content negotiation:

val format = Json {
                prettyPrint = true
                encodeDefaults = true
            }

            register(ContentType.Text.Plain, KotlinxSerializationConverter(format))

Yet the issue still persists. I would be surprised if there wasn’t something off with the format here.

Do you know if there’s docs available for this?

[Rustam Siniukov]

what is the response Content-Type header?

[Matti MK]

Unfortunately Content-Type text/html; charset=UTF-8

[Rustam Siniukov]

Then you need ContentType.Text.Html

[Matti MK]

Well, that indeed did the trick 👍

Thanks for the help, I hope there’s enough keywords in the thread so that others can find this in the future 🙂