code: public boolean isSecureLink(CmsObject cms, String vfsName, String siteRoot, boolean fromSecure) {
  
          if (siteRoot == null) {
              return isSecureLink(cms, vfsName, fromSecure);
          }
  
          // the site root of the cms object has to be changed so that the property can be read
          String storedSiteRoot = cms.getRequestContext().getSiteRoot();
          try {
              cms.getRequestContext().setSiteRoot(siteRoot);
              return isSecureLink(cms, vfsName, fromSecure);
          } finally {
              cms.getRequestContext().setSiteRoot(storedSiteRoot);
          }
      }
docs: Returns <code>true</code> if the given VFS resource should be transported through a secure channel.<p>
  
  The secure mode is only checked in the "Online" project.
  If the given OpenCms context is currently not in the "Online" project,
  <code>false</code> is returned.<p>
  
  The given resource is read from the site root of the provided OpenCms context.<p>
  
  @param cms the current users OpenCms context
  @param vfsName the VFS resource name to check
  @param siteRoot the site root where the the VFS resource should be read
  @param fromSecure <code>true</code> if the link source is delivered secure
  
  @return <code>true</code> if the given VFS resource should be transported through a secure channel
  
  @see CmsStaticExportManager#isSecureLink(CmsObject, String, String)