code: public static String getDescriptionInfo(CmsFlexController controller, HttpServletRequest req) {
  
          String result = null;
          CmsObject cms = controller.getCmsObject();
  
          try {
  
              CmsJspStandardContextBean contextBean = CmsJspStandardContextBean.getInstance(req);
              if (contextBean.isDetailRequest()) {
                  // this is a request to a detail page
                  CmsResource res = contextBean.getDetailContent();
                  // read the description of the detail resource as fall back (may contain mapping from another locale)
                  result = cms.readPropertyObject(res, CmsPropertyDefinition.PROPERTY_DESCRIPTION, false).getValue();
              }
              if (result == null) {
                  // read the title of the requested resource as fall back
                  result = cms.readPropertyObject(
                      cms.getRequestContext().getUri(),
                      CmsPropertyDefinition.PROPERTY_DESCRIPTION,
                      true).getValue();
              }
          } catch (CmsException e) {
              // NOOP, result will be null
          }
          if (CmsStringUtil.isEmptyOrWhitespaceOnly(result)) {
              result = "";
          }
  
          return result;
      }
docs: Returns the description of a page delivered from OpenCms, usually used for the <code>description</code> metatag of
  a HTML page.<p>
  
  If no description information has been found, the empty String "" is returned.<p>
  
  @param controller the current OpenCms request controller
  @param req the current request
  
  @return the description of a page delivered from OpenCms