code: private void checkUUIDOfSiteRoot(CmsSite site, CmsObject clone, CmsObject cms_offline) {
  
          CmsUUID id = null;
          try {
              id = clone.readResource(site.getSiteRoot()).getStructureId();
          } catch (CmsException e) {
              //Ok, site root not available for online repository.
          }
  
          if (id == null) {
              try {
                  id = cms_offline.readResource(site.getSiteRoot()).getStructureId();
                  m_onlyOfflineSites.add(site);
              } catch (CmsException e) {
                  //Siteroot not valid for on- and offline repository.
              }
          }
          if (id != null) {
              site.setSiteRootUUID(id);
              m_siteUUIDs.put(id, site);
          }
      }
docs: Fetches UUID for given site root from online and offline repository.<p>
  
  @param site to read and set UUID for
  @param clone online CmsObject
  @param cms_offline offline CmsObject