Message forwarded on behalf of Kevin Duffy.
> -----Original Message-----
> From: [EMAIL PROTECTED] [SMTP:[EMAIL PROTECTED]]
> Sent: Thursday, January 06, 2000 12:19 PM
> To: Drew Cox
> Subject: Re: web app programming specifications query
>
> Hi there,
>
> First, this email is in response to yours. But, I cant post to the
> jsp-interest group from work because my email address is different on this
> machine. Can you do me a favor and forward this to the group. Thanks.
>
> I have been doing some extensive talking with various authors on articles,
> books, and online chats with developers. I too have been reading about
> Model 1 and Model 2 approaches to use JSP, servlets, Javabeans, etc. I was
> worried because I read about Model 2, using the single servlet command
> setup which creates beans, populates their fields, then forwards to a JSP
> page which uses the bean to display the dynamic content the servlet stored
> in the bean. I am not doing our site like that. Instead, I follow the
> Model
> 1 a bit more, which as one author told me..its really a matter of opinion
> which you use. The model 1 dictates that your view AND controller in the
> MVC is JSP pages. That is, ALL requests first go to a JSP page, which uses
> a bean to do the logic and provide the dynamic content, that the JSP page
> then uses to display. The Model 2 uses the single servlet that uses a
> "hidden" form element (or is passed on with the request via the
> ?command=value) to "command" the servlet on what method to call, which in
> turn does what I said above..does the logic, creates a bean (or beans) to
> store the dynamic content the logic produces, and forwards to a JSP page
> to
> display it. As I see it, both do pretty much the same thing, but a bit
> differently. The Model 1 uses a JSP page as its starting point,
> instantiates a bean object (or more than 1 if the developer so desires),
> calls a method in the bean (usually passing the request and possibly the
> response object to the method, maybe named processRequest() ). That method
> uses the request object to populate various private fields via setter
> methods. With introspection, if a form data is passed, the setter methods
> that match the element names of the form are called to automatically set
> the properties of the JavaBean. Now..this is one of the areas I am not
> sure
> about..but I "think" the Model 2 approach does NOT do this. So, if it does
> not, then the JSP->JavaBean (Model 1) approach has a bit "easier"
> advantage
> there. If it does, well then they are even on that level. None the less,
> Model 1 has proven to be easier to implement and maintain (make changes,
> etc). The one thing I DONT do that Model 1 shows (in a few articles I
> read)
> is using a "controller" JSP page with lots of scriplet code in it. I use
> NO
> scriplet code except for the use of "conditional" scriplet code for
> various
> reasons (for example, to display some HTML if a given condition is met,
> otherwise display some other HTML), and the use of scriplet code to get
> the
> dynamic content.
>
> Now, something that may interest all, an author told me one thing to think
> about is that servlets, when handling multiple requests do NOT create
> multiple instances of the servlet...one for each request (storing it in
> the
> session). Instead, it is a thread context switch that occurs. This one
> item
> seems to be a performance gain in favor of the Model 2 approach. However,
> where I have my doubt is, when the servlet is called, it STILL has to
> create a bean that the JSP view page uses to display the content anyways.
> So I dont see this being such a performance gain myself. I think the
> difference lies in the scope of the javabeans in the Model 1 approach. If
> all javabeans are session scope, then they are created only once, and
> instances are instantiated from the first one in memory, which if I am
> correct, is faster than creating new objects on each request.
> Please..someone correct me if I am wrong on this as I am not quite clear
> on
> this matter. None the less, if beans are request or page scope, then each
> time that JSP page is accessed, a new bean object is created, populated
> and
> used by the JSP page, then freed. This "could" be a good thing in that the
> memory used by the bean is garbage collected after its use, whereas
> sessional beans stay alive for the duration of the session. But again I am
> not sure about this. Until more books come out to explain this stuff in
> more detail, I am relying on what I have read and some conversations I
> have
> had via email and irc.
>
> I am using the Model 1 approach because of its more simplistic
> implementation and maintenance. In my way of doing things, I use beans and
> JSP, no servlets (well, JSP = servlet..but I dont have to worry about the
> coding of the servlet). The beans are like components the way I am using
> them. One is used as a "client" bean that maintains the info of the client
> at all times (name, address, login name, password, etc) and can be updated
> at any time. Another is used to login with..its sole purpose is to log a
> client in. Another is to allow JSP pages send formatted email..they simply
> set the to, from, subject, message, bcc, cc and send it. I dont include
> ANY
> of this code on any jsp page. Now, the main thing I use scriplet code in
> is
> the use of a header and footer that EVERY page has. The header is the top
> menu bar that represents the products and various selections for those
> products. The footer is the text links to various parts of our site. In
> the
> header.inc file (its basically a jsp file but named .inc to make "more"
> sense of its use) I use various scriplet code for conditional purposes. If
> they are logged in, it displays a different menu setup. Same thing with
> the
> footer.inc. OTher than that, all pages just include the header and footer
> and do thier html stuff with some bean use thrown in to display dynamic
> content if need be.
>
> Thats my take on things. Sure would love to hear more on this topic from
> others doing similar development. Feel free to ask me any questions
> relating to this..I'll try to help in anyway I can as well. I am currently
> using Orion for development and IIS/JRUN for production (not my choice).
>
> Thanks..hope to hear from some of you.
>
>
> Kevin Duffey
> Software Engineer
> [EMAIL PROTECTED]
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