Serialize Kotlin data class constructor fields based on @JsonProperty annotations into string json. Nested non primitive fields will be serialized also but without any Annotations driving

Extension.kt

fun Any.toJsonV2(): String {
    var fieldNameToAnnotatedNameMap = [email protected] { it.name }.associateWith { fieldName ->
        val jsonFieldName =
            this@toJsonV2::class.primaryConstructor?.parameters?.first { it.name == fieldName }?.annotations?.firstOrNull { it is JsonProperty }
        val serializedName = if (jsonFieldName != null) (jsonFieldName as JsonProperty).value else fieldName
        serializedName
    }

    return buildString {
        append("{\n")
        fieldNameToAnnotatedNameMap.entries.forEach { e ->
            val field = this@toJsonV2::class.memberProperties.first { it.name == e.key }
            var value = field.javaGetter?.invoke(this@toJsonV2)
            if (value?.javaClass?.isPrimitive != true)
                value = value?.toJson()
            append("\"${e.value}\": $value")
            if (fieldNameToAnnotatedNameMap.entries.indexOf(e) != fieldNameToAnnotatedNameMap.entries.size-1)
                append(",\n")
        }
        append("\n}")
    }
}

fun Any.toJson(pretty: Boolean = false, sortAbc: Boolean = false): String {
    val objectMapper = ObjectMapper()
    if (sortAbc) objectMapper.enable(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY)
    if (pretty) {
        objectMapper.enable(SerializationFeature.INDENT_OUTPUT)
        return objectMapper.writeValueAsString(this)
    }
    return objectMapper.writeValueAsString(this).trimIndent()
}