If you are using Struts 2.0 then your action class need not extend ActionSupport.
Second important thing is textfield name in
JSP and
String variable declaration in Action class must be the same since it is case sensitive. Unless these two are same form data won't be populated in Struts2.0.
So try renaming your jsp fields to firstname, lastname, etc instead of register.firstName. register.lastName.
Hope this works.