Java EE (Java Enterprise Edition) General Discussion

For my project i need a better session handling for complexer situation than offered by the servlet package. so i decided to write a sessionmanager/handler my own.
but a lot of the features implemented in the servlet package are very useful and i will have to implement them too. so i thought, i get the source from that package an take out the code snipplets that i could need (sure i will put in the copyright note from sun). i.e. some methodes of the session tracking lilke generating the session id, or writing the session id to a cookie or rewriting the url with the session id, would be nice to get.
so i had a look at the source code but i couldn't find those methodes! the HtttpSession.java file is almost empty of code (with a lot of documentation....) and also in the HttpServletRequest.java - the same!
Can anyone tell me where i can find the code i'm looking for? I mean the code where the 'real' work is done!