code: private static URL getExtensionURL(File extension)
              throws GuacamoleException {
  
          // Validate extension file is indeed a file
          if (!extension.isFile())
              throw new GuacamoleException(extension + " is not a file.");
  
          try {
              return extension.toURI().toURL();
          }
          catch (MalformedURLException e) {
              throw new GuacamoleServerException(e);
          }
  
      }
docs: Returns a URL which points to the given extension .jar file.
  
  @param extension
  The extension .jar file to generate a URL for.
  
  @return
  A URL which points to the given extension .jar.
  
  @throws GuacamoleException
  If the given file is not actually a file, or the contents of the
  file cannot be read.