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From Sergey Beryozkin <sberyoz...@gmail.com>
Subject Re: some thoughts that I wanted to post, in regards to RP, CRI, Exceptions, and a class scanner
Date Tue, 24 May 2011 10:37:14 GMT
Hi Ryan

On Tue, May 24, 2011 at 6:28 AM, Ryan Zoerner <ryanzoerner@gmail.com> wrote:
> I have some thoughts that I wanted to post to the dev list.
>
> Here they are:
>
> The RP will need to choose between lifecylces, possibly just selecting which
> existing cxf
> resourceProvider to choose, based upon annotation. The annotations may be
> found in the
> class resource info object, obtainable from the JAXRSService. Look up the
> EJB annotations
> and find out which EJB-lifecycle this class is subscribing to, then call the
> appropriate
> cxf RP. We will need to know which cxf RP, at the time of SF.setRP(EJB_RP);
>
> "EJB_RP" will call Singleton- or per-request- RP's, or some other, based on
> @'s.
>

You are right that CXF JAX-RS EJBResourceProvider will need to make
sure EJB lifecycles are enforced properly.
But it is not what CXF itself should worry about, ResourceProvider
will just need to delegate to appropriate
EJB factory, check this link which was posted earlier on for example:

http://websvn.ow2.org/filedetails.php?repname=jonas&path=%2Fjonas%2Ftrunk%2Fjonas%2Fmodules%2Fservices%2Fwebservices%2Fcxf%2Fsrc%2Fmain%2Fjava%2Forg%2Fow2%2Fjonas%2Fws%2Fcxf%2Feasybeans%2FEasyBeansInvokerFactory.java

That is the custom implementation of CXF Invoker Factory - at the
moment CXF JAX-RS does not check such factories given that
ResourceProvider acts as the factory itself and it provides some more
information to the JAXA-RS runtime it needs when dealing with a given
invocation.

I don't  know right know if we can create  EJBResourceProvider which
would work equally well with say EJB in JBoss, Jonas, or Glassfish, as
it seems different containers provide different EJB integration
points. However, having it working with at least one container will
give us enough info to make sure a custom EJB ResourceProvider can be
provided for all EJB aware containers.

I'd personally go for JBoss or Jonas or Geronimo, because they have a
CXF JAX-WS integration. I'd try and see how CXF JAX-WS layer is
enhanced there to have EJB integrated.

For example, I'd download Jonas, and would checkout Jonas CXF JAX-WS
integration code. Then I'd ask some questions on Jonas lists or check
their docs on how to setup a CXF JAX-WS EJB endpoint. Then I'd start
Jonas in debug mode (recall the chat about the remote debugging), put
a breakpoint in EasyBeansInvokerFactory.java and run the client and
see what is going on in EJB Invoker.

Or I'd download JBoss Community Edition (see
http://www.jboss.org/jbossas/downloads/, probably 6.0), and then
either checkout the CXF JAX-WS integration code (see
http://www.jboss.org/jbossws/sourcecode.html) or download the relevant
JBoss WS/CXF source bundle. Then check these docs:
http://community.jboss.org/wiki/JBossWS-StackCXFUserGuide.

Or try Geronimo.

Before trying to debug I'd review EJB tutorials explaining how EJB
beans are created and released so that I could understand the relevant
code in Jonas/JBoss/Geronimo better.

And then, after the above process is finished, I'd just write my
custom EJBInvoker in 30 mins.

This is how I'd do it because it was a long time ago since I was doing
some work with EJB. Actually, I did a JBoss EJB test not that long
ago, but it was a security-related test I was working upon.

If you are confident and understand how EJB beans are managed then
perhaps you can start with writing a custom EJb ResourceProvider right
now.

You need to decide which container you are going to work with - I
haven't done EJB development myself so I can't recommend. Try to
select the container which will make it easier for you to get started.

>
> Exceptions: if thrown, what does cxf normally do with it? Does this vary
> between
>            exceptions. If cxf always passes it off to the server container,
> then
>            that is just fine. Need to get a list of all possible exceptions
>
>            throwable and map them to exception responses, via
> customExMapper?
>
>            will we need to have the exceptionMapper called automatically,
> so that
>            the user doesn't have to remember to set it, just to have cxf do
>
>            what user should take for grantd?
>

CXF JAX-RS will propagate a current exception if no ExceptionMapper is
found, otherwise it will
ask that mapper to convert it into HTTP response.

> What else do ejb annotation's do, besides dictate lifecycle? Does cxf
> app-lifecycle
> function handle, or need to handle any of these functions? Does java
> normally
> handle them? Does a server typically handle any of them?
>

I don't know. I think the only thing we need to worry about is about
manging the lifecycle of EJB beans

> ClassScanner idea:
> -----------------------------------------------------------------------------------
> Ok, so in terms of lifecycle management, when an ejb class is declared as a
> root
> resource, it will need to be handled by a given resourceProvider. This will
> handle the various lifecycles that EJB's provide. When the setResourceClass
> is
> called on an ejb-annotated root resource, cxf should have a mechanism in
> place
> to recognize the ejb annotation, as-such, by looking it up in a list, and
> force cxf to use the custom resource provider.

CXF JAX-RS code will only check for JAX-RS annotations. Your custom
provider will be asked to create and release instances and it will
probably won't check any annotations as well, it will just delegate to
the relevant EJB factory.
At this stage, please assume no auto discovery of EJB root resources
and providers is needed.
Assume you manually configure JAX-RS endpoints (from code or Spring),
if you can make it work then adding an auto-discovery feature will be
the easy thing to do.

> The annotations are part of
> the
> information that goes into the classResourceInfo object that resides with
> the
> JAXRSServiceFactory. There may be some way to listen for the creation of the
>
> classResourceInfo object, and then use it, at that time, to decide whether
> the
> customResourceProvider should be the default.
> -----------------------------------------------------------------------------------
>

Only the info deduced from JAX-RS annotations will make it
ClassResourceInfo. Your custom resource provider is the key piece.
I'd recommend you to get the most straighforward EJB 'case' working
first, by simplifying whatever possible, in order to see it working
and feel good about it. I actually think now that this is a very
complex project given how much info you have to filter through. I know
how seriously you are trying to approach it - but my advice is to stay
focused on the most relevant parts/info and get something working
fast.

Thanks, Sergey

> Thank you.
>
> Ryan
>



-- 
Sergey Beryozkin

Application Integration Division of Talend
http://sberyozkin.blogspot.com

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