CODEWITHSUNDEEP
jsonkotlinjson-serializationkotlinx.serialization
Karsten Gabriel
Karsten Gabriel

Reputation: 3652

Kotlinx-serialization: Serialize raw string without quotes

What I try to achieve

Using Jackson for serialization, there is the @JsonRawValue annotation to achieve that a string value is serialized without quotes. For instance, with the following code

data class SomeData {
   @JsonRawValue
   value: String
}

I can serialize SomeData("{}") and obtain:

{ "value": {} }

(Without the annotation it would be { "value": "{}" }.)

I want to achieve the same using Kotlin serialization.

Why do I want that

The reason why I want this is that I get an object via Rest, I store it in a DB, later load it from there and return it back without changing the content. It doesn't concern me what is contained in the object. So I absolutely do not need it to be parsed or deserialized in any way. In the worst case the content is altered somewhere in the process. In the best case it is just some superfluous computation.

What I tried

It seems that there is no corresponding mechanism in kotlinx-serialization that supports this out-of-the box. Looking at the source code, it seems that I would need an instance of class JsonPrimitive (or JsonLiteral) with a String value, but isString set to false, but there is no way to get that.

Another approach may be to write a serializer that serializes the String value without quotes, but I do not know how.

Upvotes: 4

Views: 3532

Answers (1)

aSemy
aSemy

Reputation: 7109

As of Kotlinx Serialization version 1.4 it is not possible to encode JSON literal strings, without quotes.

However, it will be possible in the next release! https://github.com/Kotlin/kotlinx.serialization/pull/2041#issuecomment-1287049243

For a sneak peek, have a look at the docs on the dev branch

import java.math.BigDecimal

val format = Json { prettyPrint = true }

fun main() {
    val pi = BigDecimal("3.141592653589793238462643383279")

    // use JsonUnquotedLiteral to encode raw JSON content
    val piJsonLiteral = JsonUnquotedLiteral(pi.toString())

    val piJsonDouble = JsonPrimitive(pi.toDouble())
    val piJsonString = JsonPrimitive(pi.toString())
  
    val piObject = buildJsonObject {
        put("pi_literal", piJsonLiteral)
        put("pi_double", piJsonDouble)
        put("pi_string", piJsonString)
    }

    println(format.encodeToString(piObject))
}

pi_literal is encoded literally, without being quoted.

{
    "pi_literal": 3.141592653589793238462643383279,
    "pi_double": 3.141592653589793,
    "pi_string": "3.141592653589793238462643383279"
}

Upvotes: 5

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