On Tue, 22 Feb 2000, Ernie Varitimos wrote:
> I disagree that accessing servlets through the servlet context is a
> flawed architecture. And you are wrong when you discount my
> assertion that the servlet context was not designed to group and/or
> share servlet resources. That is one of the principal reasons why it
> was created.
>
> There are of course, precautions that one should employ to guard
> against undesirable behaviors such as dynamic reloading. This can be
> managed using a number of techniques that I have iterated in other
> posts. In fact, I've created several high volume sites that use the
> servlet context to store references to sessions, object pools and
> other servlets, in single as well as multi-homed environments. It
> has proven to be effective, extensible and easy to maintain.
>
> I have yet to hear a reasonable, comprehensive explanation of why
> this is a flawed architecture and what are the superior
> alternatives. I know there are many alternatives, but I have not yet
> heard why this technique is inferior. There are several reasons why
> using the servlet context is perfectly acceptable in terms of reuse,
> collaboration and delegation (I find inheritance less desirable). I
> have also espoused out-of-the-box means of servlet collaboration,
> such as using the JSDT to distribute sessions and other objects
> across JVMs, or using reflection in concert with hidden html
> fields. But I digress.
>
> It's amazing to me that there are so many developers and some
> architects that live within the sandbox of knowledge they find in a
> few popular books or articles, as if these references represent the
> preferred ways of designing a servlet based architecture. Or they
> are so hung up on objectifying everything (OO elitists) at the
> expense of creating less readable and thus less maintainable code.
First of all, I think you may be overreacting, we don't need such
attacks here.
Second, to clarify, I think where people have the problem is not so
much with using the ServletContext and set/getAttribute to share
servlet resources, but the fact that the resources being shared are
servlets themselves.
The thinking is that servlets are interfaces to the application,
handling the request/response end of things. Other objects, whose
main job is not related to the request/response processes and probably
represent part of another layer of the application, should be
implemented as different types of objects, and not as servlets. If
you do have it as part of a servlet, likely the design will be cleaner
if you abstract out that functionality into another object. Another
way of looking at it is that things that need to be shared by servlets
should probably not be servlets themselves.
> David Mossakowski wrote:
>
> > getAttribute() in ServletContext is to share objects across servlets. It does
>allow
> > you to share the servlets themselves but that doesn't mean that this was the reason
> > for this facility. It is a side effect. One way to disable putting servlets in
> > ServletContext is to have GenericServlet NOT extend Object, the other is to not
> > allow putting Objects in ServletContext. Let's not do either :-)
> >
> > I agree with others saying that if you need to call a method of one servlet from
> > another then your architecture is flawed.
> >
> > d.
> >
> > Ernie Varitimos wrote:
> >
> > > It is simply not true that "the servlet model was not meant for such access".
> > > Otherwise the team at JavaSoft would not have provided the getAttribute() and
> > > setAttribute() methods in the ServletContext. They simply wanted to provide an
> > > architecture that made it easy to separate one servlet based application from
> > > another, yet still provide a means for servlets to communicate with one another.
> > >
> > > -ernie
> > >
> > > "Subrahmanyam A.V.B." wrote:
> > >
> > > > This has been discussed several times. Refer to the archives. FYI, the
> > > > servlet model is not meant for such access.
> > > >
> > > > Subrahmanyam
> > > >
> > > > arun prakash wrote:
> > > > >
> > > > > Hi !!,
> > > > >
> > > > > I need some help out from u guys. How can i call a
> > > > > specific servlet method from another servlet. Any
> > > > > suggestion will be extremely helpful and a code would
> > > > > be the best way to help me out.
> > > > >
> > > > > Thanks in advance.
> > > > > arun prakash
[ ... ]
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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