Servlet 2.5 今回主に取り上げるTomcat6, Jetty7で対応しているServlet 2.5の仕様を確認すると、"SRV.7.1 Session Tracking Mechanisms"で以下のように記されています。 SRV.7.1.1 Cookies Session tracking through HTTP cookies is the most used session tracking mechanism and is required to be supported by all servlet containers. The container sends a cookie to the client. The client will then return the cookie on each subsequent request to the server,