DashboardNavigator does not extend SpringNavigator

[HermanBovens]

Although this demo app is based on Spring, the custom Navigator implementation used in this demo app:

com.vaadin.demo.dashboard.DashboardNavigator

does not extend

com.vaadin.spring.navigator.SpringNavigator

and is therefore a bad example since it leads to the the following warning being logged:

c.v.spring.internal.DefaultViewCache     : The Navigator used does not extend SpringNavigator. View scope support may be limited, and future versions of Vaadin Spring may remove support for using a plain Navigator.