Parse JSON without data class in Kotlin?

Question

There are many JSON parsers in Kotlin like Forge, Gson, JSON, Jackson... But they deserialize the JSON to a data class, meaning it's needed to define a data class with the properties corresponding to the JSON, and this for every JSON which has a different structure.

But what if you don't want to define a data class for every JSON you could have to parse?

I'd like to have a parser which wouldn't use data classes, for example it could be something like:

val jsonstring = '{"a": "b", "c": {"d: "e"}}'

parse(jsonstring).get("c").get("d") // -> "e"

Just something that doesn't require me to write a data class like

data class DataClass (
    val a: String,
    val b: AnotherDataClass
)

data class AnotherDataClass (
    val d: String
)

which is very heavy and not useful for my use case.

Does such a library exist? Thanks!

Please check this answer. I believe it applies to your use case. — Bruno Gava Guerra
– Bruno Gava Guerra, Commented Jan 30, 2022 at 21:42
I guess you're refering to the answer with Klaxon. It seems to do exactly what I want, but Klaxon's Parser is deprecated. — Kureteiyu
– Kureteiyu, Commented Jan 30, 2022 at 21:52
in jackson you have org.bson.Document which acts like a sort of map. You can do .get and other things with it. I'm sure that all the others have similar objects. — AlexT
– AlexT, Commented Jan 30, 2022 at 22:09
Most, if not all, of the JSON parsers you list have generic ways to parse as well without the need to define the class — Ivo
– Ivo, Commented Jan 31, 2022 at 12:22

Михаил Нафталь · Accepted Answer · 2022-01-31 12:13:33Z

10

With kotlinx.serialization you can parse JSON String into a JsonElement:

val json: Map<String, JsonElement> = Json.parseToJsonElement(jsonstring).jsonObject

answered Jan 31, 2022 at 12:13

Михаил Нафталь

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Nikolai Shevchenko · Accepted Answer · 2022-01-31 12:39:45Z

2

You can use JsonPath

val json = """{"a": "b", "c": {"d": "e"}}"""
val context = JsonPath.parse(json)
val str = context.read<String>("c.d")
println(str)

Output:

Result: e

answered Jan 31, 2022 at 12:39

Nikolai Shevchenko

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