custom_jackson

custom_jackson.kt

object CustomDeserToTheRescue :
        ApplicationFeature<ApplicationCallPipeline, Unit, CustomDeserToTheRescue> {
        override val key: AttributeKey<CustomDeserToTheRescue> = AttributeKey("CustomDeserToTheRescue")

        override fun install(
            pipeline: ApplicationCallPipeline,
            configure: Unit.() -> Unit
        ): CustomDeserToTheRescue {
            pipeline.receivePipeline.intercept(ApplicationReceivePipeline.Transform) { receive ->
                // skip if already transformed
                if (subject.value !is ByteReadChannel) return@intercept
                // skip if a byte channel has been requested so there is nothing to negotiate
                if (subject.typeInfo.jvmErasure == ByteReadChannel::class) return@intercept

                val requestContentType = try {
                    call.request.contentType().withoutParameters()
                } catch (parseFailure: BadContentTypeFormatException) {
                    throw BadRequestException(
                        "Illegal Content-Type header format: ${call.request.headers[HttpHeaders.ContentType]}",
                        parseFailure
                    )
                }

                val type = receive.typeInfo
                val value = receive.value as? ByteReadChannel ?: throw UnsupportedMediaTypeException(requestContentType)

                val converted = withContext(Dispatchers.IO) {
                    val reader = value.toInputStream().reader(call.request.contentCharset() ?: Charsets.UTF_8)
                    Jackson.mapper.readValue(reader, type.jvmErasure.javaObjectType)
                }

                proceedWith(ApplicationReceiveRequest(receive.typeInfo, converted, reusableValue = true))
            }
            return this
        }
    }