RE: [WEB400] New System Development

["Joe Pluta" <joepluta@xxxxxxxxxxxxxxxxx>]

> From: Bartell, Aaron L. (TC)
>
> Just to make this clear, you are talking about the classes
> available in all
> of the different JDK's and third party software, not the creator classes
> that a company would have to make to facilitate the building of their own
> business logic, correct?
>
> >From how I see it most of your development time would be spent on the
> creator classes, because that is where you encapsulate all of
> your business
> logic; like the components of an order or invoice.

No, Aaron, you should have very little business logic in your Java.  That's
the point.  The Java simply talks to an RPG program, which in turn does the
business logic.  You may have to create data beans that communicate data
from the business logic to the display page, but these should be no more
complex than the record formats of a display file.  The real work is done in
the RPG program.

This is the crucial point of an n-tier design - the logic is encapsulated
very close to the database, which allows much tighter control of security
and integrity.  The messages that are sent out to the user are designed
simply to contain the data the user sees.

The side effect of this is that most data rarely leaves the host.  For
example, the data required to perform a price lookup (customer number,
product number, data ranges, total order quantity, and so on) doesn't need
to be available to the Java portion of an order entry application.  Instead,
the application simply sends the item number and quantity desired to the RPG
pricing program, which in turn returns the price.  It's much faster, and
allows much more flexibility in business rules changes.

This sort of tiered design is crucial to good web application design,
because it allows each tier of the design to focus on one specific goal, and
thus to make the best use of the language used at that tier.

Joe