通过HttpServletRequest获取real ip

public static String getIpFromRequest(HttpServletRequest request) {
        //取代理ip地址
        String ip = request.getHeader("x-forwarded-for");
        //取nginx代理设置的ip地址
        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getHeader("x-real-ip");
        }
        //从网上取的
        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getHeader("Proxy-Client-IP");
        }
        //取JAVA获得的ip地址
        if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getRemoteAddr();
        }
        //去除unkonwn
        if (ip.startsWith("unknown")) {
            ip = ip.substring(ip.indexOf("unknown") + "unknown".length());
        }
        //去除多多余的信息
        ip = ip.trim();
        if (ip.startsWith(",")) {
            ip = ip.substring(1);
        }
        if (ip.indexOf(",") > 0) {
            ip = ip.substring(0, ip.indexOf(","));
        }
        return ip;
    }