NullPointerException in AjaxViewHandler.createView

[timleung22]

Has anyone experienced a NullPointerException on line 85 of AjaxViewHandler.createView method? I am using Facelet with RichFaces 3.1.0 (same problem happens in 3.1.2.GA) and I am frequently experiencing this NullPointerException issue, while on a lucky day the page works fine.

[timleung22]

After chasing the code in the debugger, I found that the cause of the problem is that the "ajaxContext" cannot be resolved from the FacesContext, given the fact that I am using the Spring framework's DelegatingVariableResolver. In AjaxContext.java, there is this code

AjaxContext ajaxContext = (AjaxContext) context.getApplication()
.getVariableResolver().resolveVariable(context,
AJAX_CONTEXT_KEY);
if (null == ajaxContext) {
// TODO Create default implementation.
// ajaxContext = new AjaxContext();
// context.getExternalContext().getRequestMap().put(AJAX_CONTEXT_KEY,
// ajaxContext);
}
return ajaxContext;

now my AJAX_CONTEXT_KEY cannot be resolved, why is the instantiation of ajaxContext commented?
Am I missing anything on the faces-config.xml?