code: public void upgradeXmlContent(CmsObject cms) throws CmsException {
  
          if (m_xmlcontent == null) {
              CmsFile file = cms.readFile(m_resource);
              m_xmlcontent = CmsXmlContentFactory.unmarshal(cms, file);
          }
      }
docs: Unmarshalls the content of the encapsulated CmsResource and stores it within the
  CmsContentCheckResource. If the xmlcontent is already existing, it is not unmarshalled
  again.<p>
  
  @param cms the CmsObject
  @throws CmsException if loading of the content fails