how to populate the tomcat http request with account name

[engineer]

We have a Tomcat application in which each request is routed via IIS
(isapi-redirect)

IIS populates a parameter with the
active directory account name.

This is then available in Tomcat to authenticate via a call
to Active Directory.

Without the account name I cannot see how we can authenticate.

I am hoping someone can suggest an alternative way to providing
the account name without using IIS?

I have seen 3rd party products that support single sign on such as
Vintela
but these would appear to depend on the account name being
provided in the request.