Unless you have specific reasons to learn Struts, I would advise not to. Struts 1 is dead, and Struts 2 never gained anything like the traction Struts 2 had. If you want to learn a request/response-oriented framework, check out frameworks like Spring MVC and Stripes. For examples of event-oriented frameworks, have a look at
JSF 2 (*not* JSF 1) or Apache Wicket.