How to handle double posting problems

[Yee CN]

Hi,   I am new to jsf and just beginning to put together some pages. I am playing with a form that has an event listener on a selection list, the form refreshes depending on the selection. I discovered that if I click too fast jsf will throw the following exception:   01:07:42,794 ERROR [FacesServlet]:253 - Servlet.service() for servlet FacesServlet threw exception javax.faces.el.EvaluationException: Cannot get value for _expression_ '#{userBean.userIdsList}'…   What is the best way to handle this situation?   Many thanks in advance.   Yee