Why can’t I set the content type on a request? It fails saying the engine should handle the content ...

# ktor

[ribesg]

Why can’t I set the content type on a request? It fails saying the engine should handle the content type header, what does that mean?

[e5l]

You can set Content-type if you’re using OutgoingContent as body.

[ribesg]

Here is my code

private suspend fun doUploadFile(data: ByteReadChannel, uploadUrl: String, contentType: ContentType): Unit =
        http.put(uploadUrl) {
            headers.clear() // Remove default headers for this request
            contentType(contentType)
            body = object : OutgoingContent.WriteChannelContent() {

                override suspend fun writeTo(channel: ByteWriteChannel) {
                    data.copyAndClose(channel)
                }

            }
        }

[ribesg]

I get Caused by: io.ktor.http.UnsafeHeaderException: Header Content-Type is controlled by the engine and cannot be set explicitly with this code

[e5l]

Could you try something like this?

suspend fun HttpClient.doUploadFile(
        data: ByteReadChannel,
        uploadUrl: String,
        contentType: ContentType
): Unit = put(uploadUrl) {
        body = object : OutgoingContent.WriteChannelContent() {
            override val contentType: ContentType? get() = contentType

            override suspend fun writeTo(channel: ByteWriteChannel) {
                data.copyAndClose(channel)
            }

        }
    }

[ribesg]

I see. I’ve been looking a bit more at the OutgoingContent file and I saw ReadChannelContent, can I use this code instead? What’s the difference?

body = object : OutgoingContent.ReadChannelContent() {
                override fun readFrom() = data
            }

(Adding the contentType to that)

[e5l]

Yes, you can also override contentType in any OutgoingContent.

[ribesg]

How do you chose if you use a ReadChannelContent or a WriteChannelContent?

[e5l]

ReadChannelContent obliges you to provide generating channel. WriteChannelContent allows you to write content directly.

[ribesg]

So if I already have a ByteReadChannel I use ReadChannelContent, while if I have something else to write like a simple String or an InputStream I could write it directly using WriteChannelContent, am I understanding that correctly?

[ribesg]

override val contentType works, thanks.

[ribesg]

@e5l So I just realized that it uploads exactly 0 bytes

[ribesg]

Maybe I need to set the content length but it doesn’t make sense as I don’t always know the length of the ByteReadChannel

[ribesg]

Ok that was an error on my custom logger. Wasn’t splitting the channel when trying to log it