Hi. We upgraded Ktor from version 1 to 2. We use O...

# ktor

[eirikb]

Hi. We upgraded Ktor from version 1 to 2. We use OkHttp engine. After the upgrade post/put with large JSON data is sent as Transfer-Encoding: chunked. Are there any ways to prevent this? The server we communicate with doesn't support it

[eirikb]

Actually it doesn't have to be large.
This snippet will be chunked:

suspend fun main() {
    val client = HttpClient(OkHttp) {
install(ContentNegotiation) {
            jackson { }
        }
    }
    client.put("<http://localhost:1337/data>") {
        contentType(ContentType.Application.Json)
        setBody("")
    }
}

If I remove jackson it will not be chunked

[eirikb]

2022-09-01_14-48.png

[eirikb]

It seems to be fixed in 2.1.0. Looking at the release notes I'm not sure what was the fix, revert of ContentNegotiation or truncated array in ContentEncoding? https://github.com/ktorio/ktor/releases/tag/2.1.0

[Aleksei Tirman [JB]]

It isn’t fixed in Ktor 2.1.0 because the behavior you described isn’t buggy. To solve your problem you can write an implementation of the ContentConverter that will serialize objects to OutgoingContent with known content length. Here is an example:

class MyJacksonConverter(private val objectmapper: ObjectMapper = jacksonObjectMapper()): ContentConverter {
    private val originalConverter = JacksonConverter(objectmapper)

    override suspend fun deserialize(charset: Charset, typeInfo: TypeInfo, content: ByteReadChannel): Any? {
        return originalConverter.deserialize(charset, typeInfo, content)
    }

    override suspend fun serializeNullable(
        contentType: ContentType,
        charset: Charset,
        typeInfo: TypeInfo,
        value: Any?
    ): OutgoingContent {
        val writer = StringWriter()
        objectmapper.writeValue(writer, value)
        return TextContent(writer.toString(), contentType)
    }
}

Here is an example usage:

suspend fun main() {
    val client = HttpClient(OkHttp) {
        install(ContentNegotiation) {
            register(ContentType.Application.Json, MyJacksonConverter())
        }
    }
    val r = <http://client.post|client.post>("<https://httpbin.org/post>") {
        contentType(ContentType.Application.Json)
        setBody(Example(123))
    }

    println(r.bodyAsText())
}

data class Example(val x: Int)

[eirikb]

But it has been fixed in 2.1.0, they behave differently. On 2.0.3 even "" is chunked, but on 2.1.0 it is never chunked

[Aleksei Tirman [JB]]

Yes, because in 2.1.0 a string body is ignored by default in the ContentNegotiation plugin.

[Aleksei Tirman [JB]]

An object with a custom type is serialized the same way with both versions.

[eirikb]

Oh snap, you are correct. Tested with data class now, it is indeed chunked. It is not with gson though

[eirikb]

Your snippet also probably works, I just don't know how to use it since I need configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false) and I don't know where to put this setting. With the data I use it will fail without that config. gson seems to do this by default. I'm not sure if we could just swap to gson

[Aleksei Tirman [JB]]

You can create an instance of Jackson’s mapper, configure it and pass it to the constructor of MyJacksonConverter :

val mapper = ObjectMapper()
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)

val client = HttpClient(OkHttp) {
    install(ContentNegotiation) {
        register(ContentType.Application.Json, MyJacksonConverter(mapper))
    }
}

[eirikb]

That works. Thanks! 🙂