Json

@Serializable
data class Data(val id: Int, val data: String, val extensions: JsonElement)

val json = Json { ignoreUnknownKeys = true }
val instance = Data(42, "some data", buildJsonObject { put("key", "value") })

// Plain Json usage: returns '{"id": 42, "some data", "extensions": {"key": "value" } }'
val jsonString: String = json.encodeToString(instance)

// JsonElement serialization, specific for JSON format
val jsonElement: JsonElement = json.encodeToJsonElement(instance)

// Deserialize from string
val deserialized: Data = json.decodeFromString<Data>(jsonString)

// Deserialize from json element, JSON-specific
val deserializedFromElement: Data = json.decodeFromJsonElement<Data>(jsonElement)

 // Deserialize from string to JSON tree, JSON-specific
val deserializedElement: JsonElement = json.parseToJsonElement(jsonString)

// Deserialize a stream of a single item from an input stream
val sequence = Json.decodeToSequence<Data>(ByteArrayInputStream(jsonString.encodeToByteArray()))
for (item in sequence) {
    println(item) // Prints deserialized Data value
}

val defaultJson = Json {
    encodeDefaults = true
    ignoreUnknownKeys = true
}
// Will inherit the properties of defaultJson
val debugEndpointJson = Json(defaultJson) {
    // ignoreUnknownKeys and encodeDefaults are set to true
    prettyPrint = true
}