code: public CmsResource readDefaultFile(CmsResource folderResource, CmsResourceFilter resourceFilter)
      throws CmsSecurityException {
  
          return m_securityManager.readDefaultFile(m_context, folderResource, resourceFilter);
      }
docs: Returns the default resource for the given folder.<p>
  <ol>
  <li>the {@link CmsPropertyDefinition#PROPERTY_DEFAULT_FILE} is checked, and
  <li>if still no file could be found, the configured default files in the
  <code>opencms-vfs.xml</code> configuration are iterated until a match is
  found, and
  <li>if still no file could be found, <code>null</code> is returned
  </ol>
  
  @param folderResource the folder
  @param resourceFilter the resource filter
  
  @return the default file for the given folder
  
  @throws CmsSecurityException  if the user has no permissions to read the resulting file