JAVA 获取客户端请求IP(internet IP)

private static final String UN_KNOWN = "unKnown";
private static String getIpAddress() {
        if (ObjectUtils.isEmpty(RequestContextHolder.getRequestAttributes())) {
            return null;
        }
        HttpServletRequest request = ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes()).getRequest();

        String xip = request.getHeader("X-Real-IP");
        String xFor = request.getHeader("X-Forwarded-For");
        if(!StringUtils.isEmpty(xFor) && !UN_KNOWN.equalsIgnoreCase(xFor)){
            //多次反向代理后会有多个ip值，第一个ip才是真实ip
            int index = xFor.indexOf(",");
            if(index != -1){
                return xFor.substring(0,index);
            }else{
                return xFor;
            }
        }
        xFor = xip;
        if(!StringUtils.isEmpty(xFor) && !UN_KNOWN.equalsIgnoreCase(xFor)){
            return xFor;
        }
        if (StringUtils.isEmpty(xFor) || UN_KNOWN.equalsIgnoreCase(xFor)) {
            xFor = request.getHeader("Proxy-Client-IP");
        }
        if (StringUtils.isEmpty(xFor) || UN_KNOWN.equalsIgnoreCase(xFor)) {
            xFor = request.getHeader("WL-Proxy-Client-IP");
        }
        if (StringUtils.isEmpty(xFor) || UN_KNOWN.equalsIgnoreCase(xFor)) {
            xFor = request.getHeader("HTTP_CLIENT_IP");
        }
        if (StringUtils.isEmpty(xFor) || UN_KNOWN.equalsIgnoreCase(xFor)) {
            xFor = request.getHeader("HTTP_X_FORWARDED_FOR");
        }
        if (StringUtils.isEmpty(xFor) || UN_KNOWN.equalsIgnoreCase(xFor)) {
            xFor = request.getRemoteAddr();
        }
        return xFor;
    }