Thanks for the reply. I was planning to put the look up of the EJB
reference in the init method of the servlet, so unless Iam missing
something, It should be thread safe. I looked at the java pet store
source code specifically at WebControllerImpl. I found that , it looks
up the EJB reference in a non synchronized method. All the other
methods that access the EJB are synchronized, Does that mean lookups in
general are thread safe?
Appreciate your help,
Sunder
----- Original Message -----
From: "James Dasher" <[EMAIL PROTECTED]>
Date: Tuesday, January 8, 2002 7:20 pm
Subject: RE: Accessing EJB references by extending ActionServlet
> Uh, careful--synchronization issues (immediate problem) and data
> abstraction (long term problem).
> Servlets are not thread-safe, so be very careful handing that
> referencearound.
>
> Also, do you want your struts stuff knowing about EJB? EJB is
> complicated.
>
> Possible alternatives:
> 1. Use session-scope beans as web-tier Helpers, abstracting data-
> accessimplementation. (Your actions don't really need to know how
> to use an
> EJB, do they?)
> 2. Consider adding a service locator, which implements
> HttpSessionListener, which binds itself in session and knows how to
> get/create above Helper objects
> 3. Value object are a pretty good idea, too.
> 4. (Extreme) Have a single point of entry into the EJB tier, a
> controller which has one operant method, something like
>
> public synchronized ModificationResponse
> handleModification(Modification Request) {}
>
> public interface ModificationRequest {
> public String getName();
> }
>
> public interface ModifcationResponse {
> public Object getPayload();
> }
>
> Your controller (a stateful EJB) can delegate to various other
> EJB's based on an XML file or environment entries with
> ModificationRequest.getName() as the key.
>
> Your Data-Access Objects can take that response, grab the
> payload, and put it in session as needs be.
>
> Then your actions can just grab what they need likewise:
> Locator l =
> (Locator)request.getSession().getAttribute(Keys.SERVICE_LOCATOR)
> Carthelper c = l.getCartWebhelper();
>
> request.setSessionAttribute(Keys.SHOPPING_CART,c.addStuffToCart
(someItem
> ))
> where addStuffToCart returns some kind of Value Object
> you can expose as a bean. Meanwhile, your cart has been updated
> back in
> the EJB's somewhere.
>
> Most of this is ripped straight from the pages of the petstore
> demo Web
> Application Framework. If you haven't read it, it is worth it. The
> part you are looking for is
>
> petstore1.3/src/waf/src/controller/com/sun/j2ee/blueprints/waf
>
> Remember--Sun pushes EJB so you buy bigger appservers. Basically, 90%
> of the projects using EJB don't have to. If you are in the other 10%,
> then your project is large-scale enough to merit some extra time
> thinking about data abstraction.
>
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]
> Sent: Tuesday, January 08, 2002 9:17 PM
> To: Struts Users Mailing List
> Subject: Accessing EJB references by extending ActionServlet
>
>
> Hello,
> I have a design question about accessing EJB references from the
> servlet. I would like to obtain a reference to my proxy session
> bean in
> the init of the servlet and use that reference to call methods on
> the
> bean from the action classes. I have extended the ActionServlet
> and
> added additional code to the init method for the EJB lookup. I
> would
> like to know how I can pass the remote reference across the
> different
> action classes? I am not sure if putting the remote reference in
> session would be a good idea. I have all my action classes extend
> from
> the new ExtendedActionServlet
>
> Sunder
>
>
>
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