Custom security realm and spring context

I have a Tomcat based web application that uses a custom security realm. Within the security realm I need access to a spring-managed bean, but the security realm interface doesnt provide any access to the servlet context or any other way for me to get access to the spring context.

Anybody got any ideas how I could get access to the spring context? I can't initialise the security realm in spring either as it is managed by the web container.

The security realm superclass is here: SimpleSecurityRealmBase