For ASP, each page instantiated the DLL.  The action of the form was to call the appropriate next page directly.

For JSP, we will do this a bit differently.  We will still have an Address object, but the DLL class will be replaced by a servlet.  The action for all forms will call the servlet.  The servlet will determine the process to be completed, then re-direct to the appropriate next page.

The servlet as acting as a Mediator.  All communciation for the application is passed through the servlet.  This is a well-known pattern for developing applications. If you are interested in learning more about Design Patterns in Java, check out this book by James W. Cooper.

The flow works like this:

JSP calls Servlet, passing the form fields
Servlet communicates with database
Servlet creates object, if necessary
Servlet calls next JSP page
Next JSP page gets object, if necessary