gson_serialization_play_case_2.kt

object MyDateTypeAdapter : JsonDeserializer<Date>, JsonSerializer<Date> {

    private val DATE_FORMATS = arrayOf("yyyy-MM-dd HH:mm:ss", "yyyy-MM-dd")
    private val dateFormatters: List<SimpleDateFormat> = DATE_FORMATS.map { SimpleDateFormat(it, Locale.US) }
    override fun deserialize(json: JsonElement?, typeOfT: Type?, context: JsonDeserializationContext?): Date {
        for (formatter in dateFormatters) {
            try {
                return formatter.parse(json?.asString)
            } catch (ignore: ParseException) {
            }
        }

        throw JsonParseException("DateParseException: " + json.toString())
    }

    override fun serialize(src: Date?, typeOfSrc: Type?, context: JsonSerializationContext?): JsonElement {
        synchronized(designatedFormat) {
            val dateFormatAsString: String = designatedFormat.format(src)
            return JsonPrimitive(dateFormatAsString)
        }
    }
}

val gson = GsonBuilder().apply {
    registerTypeAdapter(Date::class.java, MyDateTypeAdapter)
}.create()