I agree with Robb on this.
With the 3-tier architecture, the business logic is mostly in the middle
allowing the client and the data stores to become more abstract, and
interchangable.
The servlet should not contain any business logic. It should rely on
lower level, or middle tier, objects to manipulate the data.
Although the servlet is a user interface client of the business logic, I
also look at the servlet-browser relationship as a sort of mini
client-server. The servlet creates a "frame's" display, and extracts
and sends its data to the business logic objects, but the browser
actually performs the 'show()', data display and entry.
Tim Gallagher
-----Original Message-----
From: Robb Shecter [mailto:[EMAIL PROTECTED]]
Sent: Monday, March 08, 1999 8:01 AM
To: [EMAIL PROTECTED]
Subject: Re: 3-tier architecture and Servlets
Aurelio Sanchiz Callejon wrote:
> Can be said that in a web-based application the browser is the
> client, a database server the server AND the servlets (in web server)
the
> middleware (second tier)?
> It's a simple question but I need to clarify it for theorical
purposes.
>
> Thanks
There's lots of different possible architectures, but I like to see it a
bit
differently from how you wrote it:
Database: A database. :) Typical interface: "SELECT ...".
Middle Tier: An RMI or CORBA server. Typical interface:
"performOperation(...) or
getDomainObject(...)".
Client: An applet, that connects via RMI/CORBA/XML-RPC, etc. Typical
interface:
GUI.
Alternate Client: Servlet, that generates HTML and manages state w/
impovershed
GUI environment (ie: web browsers)
So, I see servlets as simply another type of clients. These servlets
would connect
to the true middle tier with some distributed object protocol. What I'm
describing, though, is just one possibility.
- Robb
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