A comment on Servlet 3.x and modular deployment descriptors

[Tom Zeller]

I guess a compelling reason to prefer Servlet 3.x over 2.x might be
modular deployment descriptors in the form of web fragments.

Basically, a deployer wishing to add a custom servlet, for example an
ExternalAuth LoginHandler, could provide a JAR which includes the
relevant <servlet> and <servlet-mapping> definitions in
META-INF/web-fragment.xml without needing to modify the IdP's web.xml.

It seems that we have been loathe to use annotations for anything
other than documentation, so web-fragment.xml seems helpful.