@Override
 public String getPunchOutLoginUrl() {
   final String sessionId = punchoutSessionService.getCurrentPunchOutSessionId();
   if (StringUtils.isNotBlank(sessionId)) {
     final PunchOutSession punchoutSession = punchoutSessionService.loadPunchOutSession(sessionId);
     return siteBaseUrlResolutionService.getWebsiteUrlForSite(
         baseSiteService.getCurrentBaseSite(),
         "",
         true,
         getPunchOutSessionUrlPath(),
         "key=" + getPunchOutLoginAuthToken(punchoutSession) + "&sid=" + sessionId);
   }
   return null;
 }