@Jose: download the Struts source code. Read the Javadocs for the classes you mention, and read the source code.
Note that some you mention (
SuccessAction, for example), are part of the examples/cookbook. How simple can an action be, and why am I encouraging you to just *look* instead of wait? Here's the (expurgated) source code for
SuccessAction:
They're not all that easy--but
ShowSomeEffort.