Hi, we used

ktor-client-cio

to shake hands with an external APIs, but the APIs does not expose a correct ContentType header(

application/octet-stream

) as expected, the content is JSON. I tried to add a default content type to the response via the built-in

HttpSend

plugin like the following, but it did not work.

var client = HttpClient(CIO){
            install(ContentNegotiation) {
                register(ContentType.Application.Json, JacksonConverter(objectMapper))
            }
}        
client.plugin(HttpSend).intercept { builder ->
            val originalCall = execute(builder)
//            if (!originalCall.response.headers.contains(HttpHeaders.ContentType) ||
//                originalCall.response.headers[HttpHeaders.ContentType] == ContentType.Application.OctetStream.contentType
//            ) {
                originalCall.response.apply {
                    headers {
                        set(HttpHeaders.ContentType, ContentType.Application.Json.contentType)
                    }
                }
           // }
            originalCall
        }

I have tried the Apache 5 engine, it is more flexible for the

engine

config and I configured

customizeClient

customizeClient {
                    addResponseInterceptorLast(
                        HttpResponseInterceptor { response, _, _ ->
                            response.setHeader(HttpHeaders.ContentType, ContentType.Application.Json)
                        }
                    )
                }

to add an interceptor there, it worked well. But some of our team members are stick on the CIO engine.

Why registering a converter for the

application/octet-stream

content type doesn't work for you?

I want to know what is wrong in usage of

HttpSend

plugin.

You can try this workaround to override the

Content-Type

header.

We can not modify the response headers via the

HttpSendIntercepter

directly?

No, because they are immutable there

If the

HttpSendIntecepter

can not modify request/response, what is the purpose of using it?

If the

HttpSendIntecepter

can not modify request/response, what is the purpose of using it?

The purpose is to intercept the network calls to implement, for example, redirection, request retrying and so on. You can modify the request through the

HttpRequestBuilder

parameter (the

builder

parameter in your example).

And it the response is immutable there, it should not accept a

apply{}

block.

The following code just returns a new instance of

Headers

.

headers {
    set(HttpHeaders.ContentType, ContentType.Application.Json.contentType)
}

In your example, there is no code that tries to modify the response.