code: public static  String getRootDomain(HttpServletRequest request) {
  		String host = request.getHeader(WebConstants.HEADER_FORWARDED_HOST);
  		if(StringUtils.isBlank(host))host = request.getServerName();
  		
  		if(IpUtils.isIp(host) || IpUtils.LOCAL_HOST.equals(host)){
  			return host;
  		}
  		
  		String[] segs = StringUtils.split(host, POINT);
  		int len = segs.length;
  		return segs[len - 2] + POINT+ segs[len - 1];
  	}
docs: 获取根域名
  @param request
  @return