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
--
To unsubscribe, e-mail:
mailto:[EMAIL PROTECTED]
For additional commands, e-mail:
mailto:[EMAIL PROTECTED]
--
To unsubscribe, e-mail: mailto:[EMAIL PROTECTED]
For additional commands, e-mail: mailto:[EMAIL PROTECTED]
