vaadin example visual designer

I follow steps:

  1. in chrome
  2. download the war file of this example
  3. import it to eclipse
  4. navigate to this file
  5. right click this file and open it with vaadin designer
    it will throw error. I attached two pictures, and it shows the error.

How can I open this file and have a visual designer and make some change of it?

Thanks for reply

Please see a discussion about this issue