After searching web and reading your guys post, I found these two solutions for preparing for session-scope variable.
1. use traditional session event listener. When page is loaded up first time, Struts
always create a session for the user, even before it gets form bean variable value. In the session listener, we can issue some data, for example,
jdbc connection.
2. extends RequestProcessor, override its method processPreprocess(...). When each time user click some action, it will always run processPreprocess() firstly. So we can do something there, for example, JDBC connection.
If anything wrong, please correct me. This is just my research.
Thanks.