hi all, i have a somewhat complex use case for serialization for messages being communicated around ...

# serialization

[Tasos Stamadianos]

hi all, i have a somewhat complex use case for serialization for messages being communicated around a distributed system. The messages come in like so:

{
	"sessionId": "...",
	"commandId": "...",
	"message": { ... }
}

So, at a lower layer of my code, I parse the sessionId and the commandId using JsonTreeParser, and using the same parser I extract message as a JsonObject. Later on, whoever needs to use the message JsonObject can deserialize to whatever they want using mapper.readTree.

Now, say I need to serialize back to another format. Specifically:

{
	"success": true,
	"message": "...",
	"commandId": "...",
	"payload": { ... }
}

That payload field is any custom class which needs to be serializable and passed somehow, but I can't find a way to make it a JsonObject, or write any JsonObject for that matter. I also tried making a generic class with an field of the type of payload, but that didn't seem like the right direction. I guess what I'm asking is, how can I create a JsonObject from an instance of a class?

[Tasos Stamadianos]

thinking about this some more, I guess I just need a method to create that json tree by hand? and i'm not sure where to start with that

[sandwwraith]

JsonTreeMapper can convert serializable classes to json tree and back

[Tasos Stamadianos]

yes, that's exactly what i'm trying to use

[Tasos Stamadianos]

is the writeTree function what i'm looking for?

[sandwwraith]

yeah

[Tasos Stamadianos]

okay. is there some documentation I can read about it? my biggest question is how to pair an object with a String and have it serialize that. I've found some examples using `Pair<String, Int>`(for example), but the type will be generic, and from what i've read in the serialization docs about generics i'll have to write some other logic to make it work. is this the right direction?

[sandwwraith]

To serialize generic classes, you need to instantiate correct serializers for it. e.g. PairSerializer(StringSerializer, IntSerializer) for Pair<String, Int>

[Tasos Stamadianos]

ya i think i'm on to something

[Tasos Stamadianos]

could i do something like this (this does not compile yet)

fun <T: Any> writePayload(payloadSerializer: SerializationStrategy<T>, obj: T) {
        jsonTree.writeTree(Pair("payload", obj), StringSerializer to payloadSerializer)
    }

[Tasos Stamadianos]

that gives me a type mismatch though, but what i'm trying to do is say "i have a serializer for you, please use it"

[sandwwraith]

PairSerializer is a class in internal package, not a pair of serializers 🙂

[Tasos Stamadianos]

yep i think i got it

[Tasos Stamadianos]

just understood how it all works

[Tasos Stamadianos]

last step, how would i stringify a JsonTreeMapper

[sandwwraith]

You mean JsonElement -> String? Just call .toString and you would get a correct JSON.