This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
"Web Security" is a generic term that can mean anything from choosing a strong password to encryption to physically securing servers.
Struts is an implementation of the Front Controllerpattern and therefore provides no security itself.
If one wants to secure a Struts web application (i.e. require authentication and authorisation to view secured resources), one can use the JEE standard Declarative Security or a third-party product like Spring Security.