viewRoot is null

[alvaro tovar]

hello
i don't know qhy the wiew root in my page is null, some one can help to
undestand?

this happend when i change javax.faces.STATE_SAVING_METHOD to server,
googled i look that commandlink have some thing to do?, i don't know
here put this code where is throw the exception

 *public* *boolean* execute(FacesContext facesContext)
  {
    *if* (facesContext == *null*)
    {
      *throw* *new* FacesException(*"FacesContext is null"*);
    }

    *// init the View
*    Application application = facesContext.getApplication();
    ViewHandler viewHandler = application.getViewHandler();
    viewHandler.initView(facesContext);

    UIViewRoot viewRoot = facesContext.getViewRoot();


    *if* (viewRoot != *null*)
    {
      *if* (LOG.isFine())
      {
        LOG.fine(*"View already exists in the FacesContext"*);
      }
      viewRoot.setLocale(facesContext.getExternalContext().getRequestLocale());
      processComponentBinding(facesContext, viewRoot);
      *return* *false*;
    }

    String viewId = calculateViewId(facesContext);
    *// Determine if this request is a postback or initial request
*    *if* (isPostback(facesContext))
    {
      *if* (LOG.isFine())
      {
        LOG.fine(*"Request is a postback"*);
      }

      viewRoot = viewHandler.restoreView(facesContext, viewId);
      *if* (viewRoot == *null*)
      {
        *throw* *new* ViewExpiredException(
            *"No saved view state could be found for the view identifier: "*
                + viewId, viewId);