This week's book giveaway is in the Mac OS forum. We're giving away four copies of a choice of "Take Control of Upgrading to Yosemite" or "Take Control of Automating Your Mac" and have Joe Kissell on-line! See this thread for details.
In struts, data persistence is normally initiated by the Action class. Although there are a number of frameworks by which you can persist data in a database (JDO, Hibernate, Entity EJBs to name a few), the most common is JDBC. Although you could put the JDBC code into the Action class, it is much better to create another class or classes that handle data persistence, and have the action call methods on these classes.
If you don't know how to use JDBC to update a table, I'd suggest you do a search on "JDBC tutorial" and you will find many helpful suggestions on how to do this.