jQuery Grid Plugin - jqGrid

Hello, I have the servlet that before return data to jqgrid, checks if the session is expired.

This test is necessary because in the session variable I have the information  for create the SQL statement to dbms.

If session expired then the servlet return a response.sendRedirect to login page. 

Is there a way to handle this event and, for example open the popup with the message "The session is expired, you make logon again." and login button?

I can to search in documentation but I have not found information.

Kind Regards.

Giovanni.