Hi Joe,
I think that your "sooner rather than later" is here now. With products like
Ext and Ajax the server only provides data in the form of XML or JSON. The
server knows nothing about the presentation of that data. It is merely a
data source. The server never needs to send any HTML pages to the browser,
with the possible exception of the very first page in the application.
If this is the way of the future, then investing some time learning
JavaScript (especially 'OO' JavaScript) is probably a very good career move.
I find that this is an excellent way to work. The presentation layer is
exclusively browser based, using JavaScript widgets and other derived
JavaScript objects. The server has two layers - one layer comprises the
programs that send/receive data to/from the client (the client interface
layer), and the business layer which comprises a set of service programs
that contain the business logic and the interface to the database itself.
Data validation takes place in the business layer and if required error
messages (derived from i5/OS message files and associated APIs) are echoed
back to the client. The values and structure of the XML or JSON sent to the
browser indicate success or failure and the JavaScript responds accordingly,
displaying messages if required.
This approach does mean learning how to use the widgets and 'OO' JavaScript.
However, the effort is well worth the result. Excellent functionality and
really great looking browser pages can be designed quite quickly after the
initial learning curve has been passed.
Syd
-----Original Message-----
From: web400-bounces@xxxxxxxxxxxx [mailto:web400-bounces@xxxxxxxxxxxx] On
Behalf Of Joe Pluta
Sent: 17 July 2008 14:59
To: Web Enabling the AS400 / iSeries
Subject: Re: [WEB400] The "Presentation" Layer
Nathan Andelin wrote:
Microsoft invested a ton in creating UI widgets that render as HTML on the
server. Same with vendors of JSF tooling. Now we're seeing a shift to
JavaScript frameworks that render themselves as DOM objects. No HTML is
generated.
This is indeed a fundamental shift. Add to that the ability to ask for
data in small pieces a la AJAX, and what you have is Rich Client. It's
effectively a fat client framework in the browser. The entire premise
behind Web 2.0 is to remove the server-side controller and replace it
with services that are invoked by the client.
It is this shift more than anything which will sound the death knell for
the architecture Aaron proposes, where the server program dictates the
screens.
Eventually (sooner rather than later), servers will know nothing about
UI whatsoever, and will become pure message-based services. This is the
SOA model, and is a rational evolution (no pun intended) of the
client/server design.
Does that mean that JSF (and other page-at-a-time server-side
frameworks) are dead? Not yet. But they are at a disadvantage for a
lot of things.
Joe
midrange.com
