Craig R. McClanahan wrote:
> IMHO, mixing business logic and presentation -- whether in a JSP page (by
> using lots of <% %> scriptlets containing the logic) or in a servlet
> (generating the HTML code from the servlet itself) -- is not a clean design
> architecture.
The fact that architectures based on mixed business logic
and HTML are difficult to modify is not what makes using this approach a bad
idea.
On the contrary, it's the lack of good editing tools that are tightly
coupled with server-side content generators whether it be
ASP, JSP, or any other in-process thread that produces things like
recordset loops.
There have been some attempts at this, but the results I've seen
are "lock-you-in" IDE's like Visual Interdev, that create
excessive, hard-to-tune code that tends to be more cryptic than what you can
do with clean loops in your own embedded scripts.
I think the genesis of a solution will likely come from a
professional HTML page layout app product company that adds
script handling after the fact. Allaire's HomeSite is close,
but still very much a programmer's HTML editor, rather than
something that is within a graphic artist's comfort zone.
Norm
Craig R. McClanahan wrote:
>
> Sahala T Swenson wrote:
>
> > One additional thing I don't think has been mentioned, however, is the
> > fact that for HTML-heavy solutions HTML files can contain
> > <servlet></servlet> tags which call content-producing servlets. I've
> > actually found this to be great alternative to JSP since the bulk of the
> > logic resides in servlet classes and not in the HTML. I am using Sun's
> > Java Webserver to do this, however, so I'm not so certain how this works
> > with other web servers.
> >
> > Sahala
> >
>
> This is true -- just as you can use NCSA-style server side includes to include
> dynamic output from a CGI script, if you want to. But this does not address
> one of the key issues (for many people), which is a separation of HTML
> generation from Java coding.
>
> Let's take a specific example to illustrate the point. You've got a shopping
> cart application, so somewhere (presumably in an HttpSession if you're using
> servlets) you have the items that the user has selected stashed away. Now,
> you are designing the checkout page, and you have two basic alternatives for
> the part that lists the items being purchased.
>
> (1) <SERVLET> or other mechanism for server-side includes. The servlet
> that you execute has embedded HTML codes to do the formatting, as
> necessary -- for instance <TR> and </TR> tags around each item, and
> <TD> and </TD> tags around each field, because you chose (in the
> page itself) to use a <TABLE> to manage the overal format of the list.
>
> (2) JSP or page-templating mechanism that uses <LOOP> tags (or the
> equivalent for the page template language in use) to surround the
> logic for a single row, and embeds <DISPLAY> tags to retrieve just
> the data values into the HTML formatting code already present in the
> page.
>
> Either approach works. Your store site is received well, and the logic has no
> bugs in it. But, like nearly every successful web site ever built, you decide
> to do a visual makeover to freshen the look and feel. The logic of how things
> work is still OK -- you just want to modify how it is presented. Which
> approach takes more effort and coordination?
>
> (1) Change both the page that includes the <SERVLET> tag, and the HTML code
> generated by the servlet itself. In environments where the HTML is
> designed
> by a web designer, rather than a Java programmer, this means you are
> still
> forced to use the services of a Java programmer to make a "cosmetic"
> change.
>
> (2) The HTML code embedded in the JSP or page template page is modified, with
> no changes at all to the business logic that is embedded in the beans
> containing
> the shopping cart data. All changes can be made by someone familiar with
> HTML
> and the JSP or page templating system in use -- leave the Java
> programmers
> working on the next new application until you need to change the business
> logic.
>
> IMHO, mixing business logic and presentation -- whether in a JSP page (by
> using lots of <% %> scriptlets containing the logic) or in a servlet
> (generating the HTML code from the servlet itself) -- is not a clean design
> architecture. It works fine at "Hello, world" levels of complexity. It can
> indeed scale to large 100% dynamic sites that are all servlet generated.
>
> But I've written some of these large (70+ pages) 100% dynamic sites, and I am
> speaking from experience: changing appearance after the fact in this world is
> much more work, and changing the look of web sites is a constant that you have
> to plan for in large scale environments. It would be even more work in a
> mixed design that uses <SERVLET> tags to get the dynamic part, because the
> formatting HTML codes are still split between the enclosing page and the
> dynamically generated output of the servlet.
>
> Craig McClanahan
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