一、经典写法

    @Autowired
    HttpServletRequest request;
    
    String[] IP_HEADERS = {"X-Forwarded-For", "X-Real-IP", "Proxy-Client-IP", "WL-Proxy-Client-IP", "HTTP_X_FORWARDED_FOR", "HTTP_X_FORWARDED", "HTTP_X_CLUSTER_CLIENT_IP", "HTTP_CLIENT_IP", "HTTP_FORWARDED_FOR", "HTTP_FORWARDED", "HTTP_VIA", "REMOTE_ADDR"};
  
    private String getClientIpClassic()
    {
        log.info("##### Classic");
        for (String header : IP_HEADERS)
        {
            String ip = request.getHeader(header);
            if (StringUtils.isNotBlank(ip) && !StringUtils.equalsIgnoreCase("unknown", ip))
            {
                log.info("##### ip header: {}", header);
                String[] ips = ip.split(",");
                return ips[0].trim();
            }
        }
        log.info("##### request.getRemoteAddr");
        return request.getRemoteAddr();
    }

一、Lambda写法

    private String getClientIpLambda()
    {
        log.info("##### Lambda");
        return Arrays.stream(IP_HEADERS)
            .peek(log::info)
            .map(request::getHeader)
            .filter(ips -> StringUtils.isNotBlank(ips) && !"unknown".equalsIgnoreCase(ips))
            .flatMap(ips -> Arrays.stream(ips.split(",")))
            .filter(StringUtils::isNotBlank)
            .map(String::trim)
            .findFirst()
            .orElse(request.getRemoteAddr());
    }