I wanted to comment on some of the things in the response below -- I
haven't really used JSP, but some of the things seem incorrect, given
my understanding of it. Of course, if some of my comments are
incorrect, I hope someone corrects them.
On Wed, 19 Jan 2000, Shash Chatterjee wrote:
> Pere Soler Rubi wrote:
> >
> > Hi to all,
> > We are thinking about designe of a web site. We don't know what are
> > the advantages that JSP offers. We have read all the Sun's stuff, but
> > we need some in depth information. Our questions are:
>
> I have been playing with JSP lately. The advantage is that it allows
> you to separate the mechanics of HTML (or, other display client-side
> presentation technology) from the actual logic and data of the
> servlet. That is, you can have the same servlet serving up the
> data, but depending on how the JSP page that uses the servlet is
> written, the presentation can be different. Or, looking at it
> another way, you can decide to change the "look" of your pages/site
> without having to change/recompile the server. Yet another way, you
> can use the same servlet in three different places on your website
> or on three different sites and have the output look entirely
> different.
It's true that JSP does help in terms of separation of display and
logic/data, but it doesn't do it completely. More importantly, you
can't use JSP to present the output of the same servlet differently --
each JSP is compiled into a servlet, so there is a one-to-one
correspondence between JSP and servlet. (Although if you have other
classes, like beans or business logic, you could have the JSP present
the output of those differently.)
> > * Does JSP overload the server ?
>
> That I don't know from experience, but the answer probaly is that it
> depends on how much the JSP page changes, thereby requiring
> regeneration of the servlet and a recompilation. On a JSP page that
Right, but remember, this is only done once per change, no matter how
many times it is requested. And I believe some servlet engines
allow/will allow pre-compiling of changed pages so that they don't
have to wait for the first request.
> does not change, there is some extra overhead in reading the page,
> parsing it and determining which servlet to invoke, but it is
Well, as I said above, each JSP is compiled into a servlet, so after
that, there is no parsing and determining which servlet to invoke
necessary, it is the same as invoking a servlet directly (a check does
have to be made that the JSP hasn't changed, but I suppose there could
be an option to skip this check -- in conjunction with the above
pre-compilation option).
> minimal when compared to the added overhead of actually compiling
> the servlet. Overall, though, this per-page overhead would get
> multiplied by the number of JSP-page accesses and so the answer
> depends on how intensely the website is accessed. I run
> Redhat-6.1/Apache-1.3.9/JServ-1.1b3/GNUJSP-1.0 on a PIII/500/128MB
> box at home that isn't loaded at all (i.e. not connected to the
> "net"), and there is an appreciable delay the first time the JSP
> page is compiled. You can't really call this "loading", it is a
> "delay" (and understandable if you think about what is happening
> behind the scenes).
[ ... ]
Milt Epstein
Research Programmer
Software/Systems Development Group
Computing and Communications Services Office (CCSO)
University of Illinois at Urbana-Champaign (UIUC)
[EMAIL PROTECTED]
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