I highly recommend that you get a copy (can buy online in ebook form) of
"Web Development with Java Server Pages." If you look at their examples
you'll see a use of the command pattern that might help you further I think.
> -----Original Message-----
> From: A mailing list about Java Server Pages specification and reference
> [mailto:[EMAIL PROTECTED]]On Behalf Of Hines, Bill
> Sent: Thursday, May 25, 2000 4:34 AM
> To: [EMAIL PROTECTED]
> Subject: Re: Model 2 - Instantiate Action & Call doGet()?
>
>
> Craig,
>
> I understand. One thing, however - I still was going to have the main
> "controller" servlet that was going to do the routine things - check for
> login, check for session, etc. Then *that* controller servlet was going to
> instantiate the Action servlet and call its doGet(). But as you say, that
> would be overkill since the Action servlet would carry a lot of
> unnecessary
> baggage.
>
> Am I right that your Action classes then just each extend the Action
> interface and have just the one perform() method? And the Action class is
> the one that forwards to the correct JSP page?
>
> Thanks, Bill
>
> -----Original Message-----
> From: Craig R. McClanahan [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, May 24, 2000 12:50 PM
> To: [EMAIL PROTECTED]
> Subject: Re: Model 2 - Instantiate Action & Call doGet()?
>
>
> "Hines, Bill" wrote:
>
> > In the model 2 architecture that many of you use, is the Action class
> > derived from HttpServlet? I saw a code example where I think it was a
> > generic class, but passed in the calling servlet, request, and response.
> > Would it be better to just make it a servlet and instantiate it and then
> > call its doGet(), passing in the request and response? If possible, this
> > might allow me to more easily port an existing app to this architecture.
> >
>
> In my case, the Action interface (not really a class) is *not* a
> servlet --
> it has
> one method:
>
> public interface Action {
>
> public void perform(HttpServlet servlet,
> HttpServletRequest request,
> HttpServletResponse response)
> throws IOException, ServletException;
>
> }
>
> It is certainly possible to make each action a servlet -- and
> then it's even
> possible to call them directly instead of going through a controller.
> However,
> I've found the following disadvantages to this for my own apps
> (your mileage
> may
> vary):
>
> - You lose the fact that the controller servlet
> can perform common logic (such as making
> sure you've logged on) for all requests -- you
> would now need to make sure that this is
> done in every single action servlet.
>
> - You tend to create subtle dependencies between
> the presentation logic and the business logic
> based on the URLs being used. I find it easier
> to avoid this temptation if I'm using an action
> class that is clearly not a servlet.
>
> - If your action procedures don't need the full
> lifecycle support (init and destroy methods) that
> servlets support, making them servlets is overkill.
> (If they do need this support, maybe you should
> look at designing them to access shared servlet
> context attributes that are initialized when the
> server starts up instead?).
>
> For some folks, action servlets works just fine because they don't need a
> single
> point of management. Personally, I find it easier to separate roles, and
> design my
> action classes as "adapters" (in Design Patterns terms) between the
> parameters
> coming in with the HTTP request, and the business logic beans or EJBs that
> actually
> do things.
>
> >
> > Thanks, Bill
> >
>
> Craig McClanahan
>
> ==================================================================
> =========
> To unsubscribe: mailto [EMAIL PROTECTED] with body: "signoff
> JSP-INTEREST".
> Some relevant FAQs on JSP/Servlets can be found at:
>
> http://java.sun.com/products/jsp/faq.html
> http://www.esperanto.org.nz/jsp/jspfaq.html
> http://www.jguru.com/jguru/faq/faqpage.jsp?name=JSP
> http://www.jguru.com/jguru/faq/faqpage.jsp?name=Servlets
>
> ==================================================================
> =========
> To unsubscribe: mailto [EMAIL PROTECTED] with body: "signoff
> JSP-INTEREST".
> Some relevant FAQs on JSP/Servlets can be found at:
>
> http://java.sun.com/products/jsp/faq.html
> http://www.esperanto.org.nz/jsp/jspfaq.html
> http://www.jguru.com/jguru/faq/faqpage.jsp?name=JSP
> http://www.jguru.com/jguru/faq/faqpage.jsp?name=Servlets
>
===========================================================================
To unsubscribe: mailto [EMAIL PROTECTED] with body: "signoff JSP-INTEREST".
Some relevant FAQs on JSP/Servlets can be found at:
http://java.sun.com/products/jsp/faq.html
http://www.esperanto.org.nz/jsp/jspfaq.html
http://www.jguru.com/jguru/faq/faqpage.jsp?name=JSP
http://www.jguru.com/jguru/faq/faqpage.jsp?name=Servlets
