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If you have used MountMapper for your custom mappers in Wicket 1.5/6.x then now your custom mapper has to extend from AbstractBookmarkableMapper.
AuthenticatedWebApplication#onUnauthorizedPage WICKET-5490
The type of the parameter passed to AuthenticatedWebApplication#onUnauthorizedPage() has changed from org.apache.wicket.Page to org.apache.wicket.Component because this is an instance of a page that is partially constructed. Only the constructor of org.apache.wicket.Component is fully executed. All super constructors are not executed and the instance is not really a Page.
Behavior changes
org.apache.wicket.request.Url#getQueryString WICKET-4664
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