Tomcat: Caching SWF files with varying query strings

Question

I'm current loading my SWF from a JSP, and passing parameters to it via query string (e.g. flash.swf?key=1234abcd) which works fine. The problem is that this appears to disable caching completely. My users will likely visit my Flash app with a different query string every time, which will lead to long load times.

I see in the headers there is an ETag, which would be respected if not for the varying query string. Is there another way to pass parameters to the SWF (headers maybe?) which still allows it to be cached?

Using Tomcat 6.0 BTW.