@Nullable
    @Override
    public TransportType transportType() {
        final String strTransportType = getNormalized("transportType");
        if (strTransportType == null) {
            return null;
        }
        switch (strTransportType) {
            case "nio":
                return TransportType.NIO;
            case "epoll":
                return TransportType.EPOLL;
            case "io_uring":
                return TransportType.IO_URING;
            default:
                throw new IllegalArgumentException(String.format("%s isn't TransportType", strTransportType));
        }
    }
Implementation of {@link FlagsProvider} which provides values from JVM options to {@link Flags}.
core/src/main/java/com/linecorp/armeria/common/SystemPropertyFlagsProvider.java