Why doesn't Java's request.getAttributeNames() show Shibboleth attributes?

[Peter Schober]

* Philip Durbin <philip_durbin at harvard.edu> [2015-06-19 21:37]:
> p.s. It works just fine, by the way, to print attributes that I look
> up one by one with this:
> 
> request.getAttribute("Shib-Identity-Provider")

I experienced and reported the same thing 5 years ago, but my usage of
the APIs involved my just be the cause:
https://lists.internet2.edu/sympa/arc/shibboleth-users/2010-06/msg00233.html
https://lists.internet2.edu/sympa/arc/shibboleth-users/2010-06/msg00240.html
-peter