I dont have much knowledge about struct, but what i know about struct is that
its a Controller in MVC framework. Controller in the sense that there exist one
servelet which is registered in default_app.xml file used for registering
servelets and with that there exist a configuration file which have request name
to java class mappings. With each request a request name is appended and then
this servelet using the request name maps and passes the request object to that
class. The java class then processes the request and returns a page name which
is nothing but the name of the JSP page which will be loaded.

Therefore Struct acts as a Controller where it passes the request object to
appropriate class.

This is just a introduction to Structs and there are plenty of other features of
Structs.

I am a fresher so i dont know weather i answered your question properly or not.