Chris,
Yes I did experiment this approach and it worked great. Many people may think
we are adding too many layers to accomplish the tasks but I believe this
approach gives a very clean separation between the biz logic and presentation
layers.
Something to note. I found that "useBean" is kind of misleading for EJB
developers because it doesn't refer to Entreprise Beans to me. I implemented
the command pattern using just a 'regular' class which interacts with an ejb
session bean. I still use the "useBean" tag to instanciate (automaticly) my
'regular' java class. I believe that is the way you did as well. I am correct
?
Dovan
"DeGreef, Chris J. (AIT)" wrote:
> I have had good luck with a similar design. Here is what I do in cases like
> this. Most of this was found by reading articles / books and trial and
> error.
>
> In a JSP file I use the "useBean" to create / find a bean that resides in
> the same VM as the servlet engine. This bean follows the command pattern.
> When it is executed it creates a session bean (on the EJB container), pushes
> the data into the session bean, and generally interacts with it. Most
> likely the session bean updates some of its instance variables during this
> time. Just before the execute is completed, the command class pulls the
> variables back into it (refreshed). At critical moments the session bean
> may have interacted with entity beans, if necessary.
>
> The command classes never talk directly to entity beans (perhaps bypassing
> imporant business logic) and the JSPs never talk to anything except the
> command classes.
>
> The command classes provide a tidy place to handle all of the JSP data
> conversion requirements; like converting the information to and from string
> representations. It also allows you to control the communication to the EJB
> container. For instance, all of the data could be sent (or retrieved) in
> one message send.
>
> The session beans are a good place to put all of the business logic.
>
> The entity beans are a good place to handle all of the data mapping issues.
>
> Has anyone had experience implementing this pattern on a large scale? (large
> volume?)
>
> -----Original Message-----
> From: Hunter Hillegas [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, May 16, 2001 1:03 PM
> To: JBoss 2
> Subject: [JBoss-user] Design Question
>
> Okay... Starting the design on my first ever EJB/JBoss project. It's only
> going to be accessible via the Web...
>
> I want to make sure I make an educated decision on the design.
>
> This is what I'm thinking:
>
> Requests come in via a servlet, which invokes methods on a stateless session
> bean that uses CMP entities to create details objects, which are placed in
> the request scope for JSPs to display.
>
> For parts of the site that are transactional, input will be received by the
> servlet then fired off to the appropriate stateless session beans and then
> to the entities as necessary.
>
> Any major flaws in this generic description? It seems to be similar to what
> sites like TheServerSide.com have implemented but since I've never done this
> before, I may be misunderstanding something basic. It seems like creating
> read-only details objects are the best way to push content out to the JSPs
> for display. Is there another approach (besides calling entities directly -
> this seems way too expensive) that I am ignoring?
>
> Hunter
>
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