SSO broken when upgrading from spring-boot 2.1.10 to 2.2.0 / 2.2.1

[jonfreedman]

Updating to the latest minor version of spring-boot 2.2.0 / 2.2.1 from the immediate prior version 2.1.10 causes SSO to stop working with InternalResourceView#prepareForRendering throwning a ServletException due to a circular view path.

This manifests itself with the client being served a HTTP 500 with the WWW-Authenticate: Negotiate header rather than a HTTP 401.

This seems to be due to updating spring-webmvc from 5.1.11 to 5.2.0 / 5.2.1

[jonfreedman]

I've started to narrow this down, which this ServletException is thrown the ViewResolver implementation in my application changes from a UrlBasedViewResolver to a InternalResourceViewResolver instance.

The cause of this was that the default Freemarker extension was changed from .ftl to .ftlh, so when I renamed login.ftl to login.ftlh the issue was resolved.