获取web客户端的IP

public static String getIp(final HttpServletRequest request) {
        String ip = request.getHeader("x-forwarded-for");
        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getHeader("Proxy-Client-IP");
        }
        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getHeader("WL-Proxy-Client-IP");
        }
        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getHeader("HTTP_CLIENT_IP");
        }
        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getHeader("HTTP_X_FORWARDED_FOR");
        }
        // 多级反向代理
        if (null != ip && !"".equals(ip.trim())) {
            StringTokenizer st = new StringTokenizer(ip, ",");
            while (st.hasMoreTokens()) {
                String _ip = st.nextToken();
                if (!"unknown".equalsIgnoreCase(_ip.trim())) {
                    return _ip.trim();
                }
            }
        }
        ip = request.getRemoteAddr();
        if (ip != null) {
            ip = ip.trim();
        }
        return ip;
    }