Error 500 : No action instance could be created

[M . Amin]

Dear all,
 when i tried the example application "/example/logon.do uri" i got the
following error message :
  
 Error: 500

Location: /example/logon.do

No action instance for path /logon could be created.

Is there any thing missed to be configured to run this example application ?
any help will be appreciated.

Regards,
 M. Amin