How can I ensure T has Serializable, and call .ser...

# announcements

[Alex Spence]

How can I ensure T has Serializable, and call .serializer() ?

[Marc Knaup]

You can't. Serializers can be created for any types even if they aren't @Serializable. Why do you need them to be of a specific type?
The library uses SerialModule for registering additional serializers at runtime.

[Alex Spence]

I guess I'm not understanding how to get a serializer instance from T

[Alex Spence]

And also pass json.parse<T> - I get an error because the type is refied

[Alex Spence]

I would like to convert this code to a generic Serde<T>

[Alex Spence]

class QueryRequestSerde: Serde<QueryRequest> {
    override fun configure(configs: MutableMap<String, *>?, isKey: Boolean) {}

    override fun deserializer(): Deserializer<T> = QueryRequestDeSerializer()

    override fun close() {}

    override fun serializer(): Serializer<QueryRequest> = QueryRequestSerializer()
}

class QueryRequestDeSerializer: Deserializer<QueryRequest> {
    private val json = Json(JsonConfiguration.Stable)

    override fun configure(configs: MutableMap<String, *>?, isKey: Boolean) {}

    @ImplicitReflectionSerializer
    override fun deserialize(topic: String?, data: ByteArray?): T? {
        return if (data != null)
            json.parse(QueryRequest.serializer(), data.toString(Charsets.UTF_8))
        else null
    }

    override fun close() {}
}

class QueryRequestSerializer: Serializer<QueryRequest> {
    override fun configure(configs: MutableMap<String, *>?, isKey: Boolean) {}

    @ImplicitReflectionSerializer
    override fun serialize(topic: String?, data: QueryRequest?): ByteArray? {
        return if (data != null)
            json.stringify(QueryRequest.serializer()).toByteArray(Charsets.UTF_8)
        else null
    }

    override fun close() {}

    private val json = Json(JsonConfiguration.Stable)
}

[Marc Knaup]

It T is @Serializable and not generic then you can use T::class.serializer().
That means you need the KClass of T.

[Marc Knaup]

Then you call .stringify() with both, the serializer and the instance to serialize.

[Marc Knaup]

So when you create an instance of YourGenericSerde you'll likely have to pass the KClass<T> to it because you have no other way of accessing it.

[Marc Knaup]

Even better would be to pass KSerializer directly for more flexibility and you wouldn't have to rely on reflection which btw only works on the JVM.

[Alex Spence]

@Serializable
data class QueryRequest(val metrics: List<MetricQueryRequest>) {
    companion object {
        val serde = JsonSerde(serializer())
    }
}

data class MetricQueryRequest(val metricDefinition: String, val parameters: Map<String, *>)


class JsonSerde<T>(private val serializer: KSerializer<T>): Serde<T> {
    private val json = Json(JsonConfiguration.Stable)

    override fun deserializer(): Deserializer<T> = JsonDeserializer()
    override fun serializer(): Serializer<T> = JsonSerializer()

    override fun configure(configs: MutableMap<String, *>?, isKey: Boolean) {}
    override fun close() {}

    inner class JsonDeserializer: Deserializer<T> {
        @ImplicitReflectionSerializer
        override fun deserialize(topic: String?, data: ByteArray?): T? {
            return if (data != null)
                json.parse(serializer, data.toString(Charsets.UTF_8))
            else null
        }

        override fun close() {}
        override fun configure(configs: MutableMap<String, *>?, isKey: Boolean) {}
    }

    inner class JsonSerializer: Serializer<T> {
        override fun serialize(topic: String?, data: T): ByteArray? {
            return if (data != null)
                json.stringify(serializer, data).toByteArray(Charsets.UTF_8)
            else null
        }

        override fun configure(configs: MutableMap<String, *>?, isKey: Boolean) {}
        override fun close() {}
    }
}

[Alex Spence]

Looks like it will work, thanks for the help