public static String getHost()

in shenyu-common/src/main/java/org/apache/shenyu/common/utils/IpUtils.java [107:180]
64 lines of code
21 McCabe index (conditional complexity)

    public static String getHost(final String filterHost) {
        String hostIp = null;
        String pattern = filterHost;
        // filter matching ip
        if ("*".equals(filterHost) || "".equals(filterHost)) {
            pattern = null;
        } else if (Objects.nonNull(filterHost) && !filterHost.contains("*") && !isCompleteHost(filterHost)) {
            pattern = filterHost + "*";
        }

        // if the progress works under docker environment
        // return the host ip about this docker located from environment value
        String dockerHostIp = System.getenv(SYSTEM_ENV_DOCKER_HOST_IP);
        if (Objects.nonNull(dockerHostIp) && StringUtils.isNoneBlank(dockerHostIp)) {
            return dockerHostIp;
        }

        // Traversal Network interface to scan all network interface
        List<NetCard> ipv4Result = new ArrayList<>();
        List<NetCard> ipv6Result = new ArrayList<>();
        NetCard netCard;
        try {
            Enumeration<NetworkInterface> enumeration = NetworkInterface.getNetworkInterfaces();
            while (enumeration.hasMoreElements()) {
                final NetworkInterface networkInterface = enumeration.nextElement();
                Enumeration<InetAddress> addresses = networkInterface.getInetAddresses();
                while (addresses.hasMoreElements()) {
                    InetAddress inetAddress = addresses.nextElement();
                    if (Objects.nonNull(inetAddress) && !inetAddress.isLoopbackAddress()) {
                        if (inetAddress instanceof Inet4Address && isCompleteHost(inetAddress.getHostAddress())) {
                            netCard = new NetCard(inetAddress.getHostAddress(),
                                    getName(networkInterface.getName()),
                                    getNamePostfix(networkInterface.getName()),
                                    Integer.parseInt(inetAddress.getHostAddress().split("\\.")[3]));
                            ipv4Result.add(netCard);
                        } else {
                            netCard = new NetCard(inetAddress.getHostAddress(),
                                    getName(networkInterface.getName()),
                                    getNamePostfix(networkInterface.getName()));
                            ipv6Result.add(netCard);
                        }
                    }
                }
            }

            // sort ip
            Comparator<NetCard> byNamePostfix = Comparator.comparing(NetCard::getNamePostfix);
            Comparator<NetCard> byIpv4Postfix = (card1, card2) -> card2.getIpv4Postfix() - card1.getIpv4Postfix();
            ipv4Result.sort(BY_NAME.thenComparing(byNamePostfix).thenComparing(byIpv4Postfix));
            ipv6Result.sort(BY_NAME.thenComparing(byNamePostfix));
            // prefer ipv4
            if (!ipv4Result.isEmpty()) {
                if (Objects.nonNull(pattern)) {
                    for (NetCard card : ipv4Result) {
                        if (ipMatch(card.getIp(), pattern)) {
                            hostIp = card.getIp();
                            break;
                        }
                    }
                } else {
                    hostIp = ipv4Result.get(0).getIp();
                }
            } else if (!ipv6Result.isEmpty()) {
                hostIp = ipv6Result.get(0).getIp();
            }
            // If failed to find,fall back to localhost
            if (Objects.isNull(hostIp)) {
                hostIp = InetAddress.getLocalHost().getHostAddress();
            }
        } catch (SocketException | UnknownHostException ignore) {
            hostIp = LOCALHOST;
        }
        return hostIp;
    }