AbstractDatabaseManager.kt

override fun getPlayerId(uuid: UUID) =
    synchronized(this) {
        if (playerMap.contains(uuid)) {
            return@synchronized playerMap[uuid]!!
        }

        // We don't have this UUID cached, so check the database
        var result: Int? = null
        // byte array representation of the UUID
        val array = uuid.toByte()
        connection.use {
            result = getFirstColumn("SELECT p.id FROM players p WHERE p.uuid = ?", array)

            if (result == null) {
                // This uuid isn't in the database yet, so add it
                val name = plugin.getPlayerName(uuid)

                // Only add it to the database if we can actually get a player name
                if (name != null) {
                    executeUpdate("INSERT INTO players (uuid, name) VALUES (?, ?)", array, name)

                    result = getFirstColumn("SELECT p.id FROM players p WHERE p.uuid = ?", array)
                }
            }
        }

        if (result != null) {
            playerMap[uuid] = result!!
        }

        return@synchronized result
    }