获取客户端的真实IP

/**
     * 获取真实IP地址
     * <p>使用getRealIP代替该方法</p>
     * @param request req
     * @return ip
     */
    public static String getClinetIpByReq(HttpServletRequest request) {
        // 获取客户端ip地址
        String clientIp = request.getHeader("x-forwarded-for");

        if (clientIp == null || clientIp.length() == 0 || "unknown".equalsIgnoreCase(clientIp)) {
            clientIp = request.getHeader("Proxy-Client-IP");
        }
        if (clientIp == null || clientIp.length() == 0 || "unknown".equalsIgnoreCase(clientIp)) {
            clientIp = request.getHeader("WL-Proxy-Client-IP");
        }
        if (clientIp == null || clientIp.length() == 0 || "unknown".equalsIgnoreCase(clientIp)) {
            clientIp = request.getRemoteAddr();
        }
        /*
         * 对于获取到多ip的情况下，找到公网ip.
         */
        String sIP = null;
        if (clientIp != null && !clientIp.contains("unknown") && clientIp.indexOf(",") > 0) {
            String[] ipsz = clientIp.split(",");
            for (String anIpsz : ipsz) {
                if (!isInnerIP(anIpsz.trim())) {
                    sIP = anIpsz.trim();
                    break;
                }
            }
            /*
             * 如果多ip都是内网ip，则取第一个ip.
             */
            if (null == sIP) {
                sIP = ipsz[0].trim();
            }
            clientIp = sIP;
        }
        if (clientIp != null && clientIp.contains("unknown")){
            clientIp =clientIp.replaceAll("unknown,", "");
            clientIp = clientIp.trim();
        }
        if ("".equals(clientIp) || null == clientIp){
            clientIp = "127.0.0.1";
        }
        return clientIp;
    }

/**
 * 判断IP是否是内网地址
 * @param ipAddress ip地址
 * @return 是否是内网地址
 */
public static boolean isInnerIP(String ipAddress) {
    boolean isInnerIp;
    long ipNum = getIpNum(ipAddress);
    /**
     私有IP：A类  10.0.0.0-10.255.255.255
     B类  172.16.0.0-172.31.255.255
     C类  192.168.0.0-192.168.255.255
     当然，还有127这个网段是环回地址
     **/
    long aBegin = getIpNum("10.0.0.0");
    long aEnd = getIpNum("10.255.255.255");

    long bBegin = getIpNum("172.16.0.0");
    long bEnd = getIpNum("172.31.255.255");

    long cBegin = getIpNum("192.168.0.0");
    long cEnd = getIpNum("192.168.255.255");
    isInnerIp = isInner(ipNum, aBegin, aEnd) || isInner(ipNum, bBegin, bEnd) || isInner(ipNum, cBegin, cEnd)
            || ipAddress.equals("127.0.0.1");
    return isInnerIp;
}

private static long getIpNum(String ipAddress) {
    String[] ip = ipAddress.split("\\.");
    long a = Integer.parseInt(ip[0]);
    long b = Integer.parseInt(ip[1]);
    long c = Integer.parseInt(ip[2]);
    long d = Integer.parseInt(ip[3]);

    return a * 256 * 256 * 256 + b * 256 * 256 + c * 256 + d;
}

private static boolean isInner(long userIp, long begin, long end) {
    return (userIp >= begin) && (userIp <= end);
}

原文地址：https://www.cnblogs.com/jimw/p/9968845.html