Can anybody give me a hint, how I can access the actual response body in a ktor server plugin within...

# ktor

[Ulrich Winter]

Can anybody give me a hint, how I can access the actual response body in a ktor server plugin within the ResponseBodyReadyForSend hook?
I have found the onCallRespond callback, but I want to be sure, that I get the final response body content which is not further transformed or modified before sent to the client.

[Aleksei Tirman [JB]]

The second parameter of the handler for on(ResponseBodyReadyForSend) is the response body after all transformations.

[Aleksei Tirman [JB]]

val plugin = createApplicationPlugin("myplugin") {
    on(ResponseBodyReadyForSend) { call, content ->
        println(content)
    }
}

[Ulrich Winter]

The second param is of type OutgoingContent which has several properties like contentType, headers, status but none for the response body itself.
How doe I get the response body from that content?

[Aleksei Tirman [JB]]

Since OutgoingContent is a sealed class, you can check the actual type and, depending on it, read the body. Here is an example:

on(ResponseBodyReadyForSend) { call, content ->
    when(content) {
        is OutgoingContent.ByteArrayContent -> {
            content.bytes() // ByteArray
        }

        is OutgoingContent.ReadChannelContent -> {
            content.readFrom() // ByteReadChannel
        }

        // ...
    }
}

[Ulrich Winter]

Thank you.

[Ulrich Winter]

one more question: it seems, adding another header within ResponseBodyReadyForSend is not possible, because:
• adding it to ``call.response.headers` has no effect
• modifying content.headers is not possible, as io.ktor.http.Headers has no methods for appending an header
Right?

[Aleksei Tirman [JB]]

Appending a header through call.response.headers should work.

[Ulrich Winter]

yes, that works!