Custom HttpAccountingInfo information

I'm hoping this is a simple question that just proves the depths of my stupidity. I'm attempting to add custom fields to the extended access log. I've successfully followed the documentation to add a custom logger and add a field to the log line, but I cannot figure out how information gets IN to the HttpAccountingInfo object. Does anyone have a reference on how to add custom data to HttpAccountingInfo when processing a servlet?

Thanks,

Mike