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From Christian Beikov <christian.bei...@gmail.com>
Subject Re: [CODI] CODI v1.0.5 + WebSphere v8.5.0.1 problem
Date Thu, 13 Dec 2012 00:38:54 GMT
Am 13.12.2012 00:45, schrieb Denis Forveille:
>
> Le 2012-12-12 18:27, Christian Beikov a écrit :
>> Sorry I mixed up your 3 emails a bit. Answers inline.
>>
>>
>> Am 13.12.2012 00:01, schrieb Denis Forveille:
>>> This is the pattern defined by Seam 2 all the way and the assumption 
>>> on which it has been designed on first place...
>>>
>>> I don't really understand your points, mostly I think because it 
>>> seems you describe patterns we don't use..
>> If you don't use "open session/entitymanager/connection in view" the 
>> "patterns" I tried to describe are not so different from what I 
>> understand about yours now.
>>>
>>> At high level, our classes are organized like this :
>>> - "Managers" classes in SLSB  ("Event/ Scope/stateless..). Manager 
>>> provides generic function tied to a "business domain" (Customer, 
>>> orders) and deal with the database common access (get a "Customer" 
>>> list) or service (communicate with external systems)
>> Your Managers are all stateless then, did I get that right?
>> If so, this is what I meant by using something like application 
>> scope, singleton or stateless so that's fine then.
> As stated in my previous post, yes. Application or Singleton are not 
> that OK because you have to manage concurrent acess to methods in thos 
> beans. SLSB do that  natively for us, and this very fast (SLSB are 
> pooled..)
If your managers are stateless you obviously have no shared state that 
has to be protected by using synchronization constructs. The only thing 
that is probably accessed concurrently is your EntityManager proxy. 
Although the proxy already handles concurrency and you don't have to 
take care of that anyway. If you are not using. Instances of your SLSBs 
are accessed concurrently anyway, there happens no synchronization at 
all(if it would be different i would not use stateless any more). The 
pooling is nice, although I don't think that it will actually improve 
performance. Since there are no declarative standard mechanisms like CMT 
for simple POJOs yet, you definetly should use SLSBs for your managers. 
My point was just that the lifetime of the beans in the mentioned scopes 
would be "the same". Although it's not that simple but since you are 
using SLSBs already anyway, stick to them.
>>> - "Controllers" classes in SFSB either in View/Page or Conversation 
>>> scope. A controller is basically a JSF backing bean, handling one or 
>>> many (wizards) views. They can also access the databse (Very if this 
>>> customer already exist or can delegate this to a manager)
>> What I don't get is why you need SFSBs for your controllers. Why not 
>> making them simple POJOs? Also in my opinion, letting the controllers 
>> access the db directly is no good idea. Why not put these data access 
>> methods into your managers or so?
> Because the EJB Container manage the transaction for us and SFSB are 
> the perfect construction for "stateful" data, assigned to one 
> "client". So the controleur can acces many methods in different 
> "managers" in the same transaction natively (eg without extra 
> construction or CODI/@Transaction annotations for example) and this 
> even if the SFSB does not directly access the DB..
As far as I understood that, you start a transaction on every access to 
a public method of your SFSB. Isn't that a bit of an overkill and also 
waste? IMO the granularity of the transaction should be finer than that. 
If you are using JSF I can't imagine how many "useless transactions" are 
started and stopped just for retrieving values from your backing bean. 
You could of course define @TransactionAttribute(SUPPORTS) on every 
method that should not start a transaction but that's ugly. When you 
access your SLSB from within a POJO the transaction is started by the 
SLSB, or to be more specific by an interceptor that attached 
automatically on your SLSB, if you didn't change the transaction 
attribute for the manager.
So mainly if you don't require the transaction to involve a whole method 
of your SFSB, and you shouldn't IMO, you don't need SFSBs. It's just 
okay to have POJOs. If you really need the transaction over a whole SFSB 
method, you probably added logic that should have been in your managers 
instead of your backing bean.
Regarding concurrency I can only say that, if you have concerns and 
therefore use SFSBs you probably use the wrong scope. Although you might 
run into situations where you really need synchronization it is in 
general the rare case when you used the right scope.
> With EJB 3.1, EJBs are "transparent" (no interfaces, no super class, 
> no extra constructions), the only difference with a POJO is the 
> @Stateful annotation and you benefit from the EJB container features)
There are other differences too. For example if you throw a 
non-ApplicationException within an EJB, your instance gets destroyed. 
 From my experiences I can only say that this behavior sucks. Of course 
you can annotate a top level exception type with 
@ApplicationException(inherited=true) and force yourself to only throw 
these kinds of exceptions, but you will probably end up having a lot try 
catches...
>>> - "Managers" are only accessed from Controlers
>> Good.
>>>
>>> - some POJOs (Usually conversation scoped to handle data used by 
>>> many pages in a conversation)
>> That's nice too.
>>> - and detached entities directly display in the presentation layer..
>> so you don't use "open session/entitymanager/connection in view" 
>> right? :D
> No
>>>
>>> Sean 2 automatically discard the SFSB when the conversation ends
>> Same for Codi conversation and the default CDI conversation, isn't it?
> Yes (I think..lol, learning CDI now, trying to migrate our Seam 2 apps..)
>>>
>>> All our apps are architectured like this and this is great ! This 
>>> works very well this way our apps are very clear and concise wit the 
>>> controler/manager separation. No "dao" no transport layers or "extra 
>>> wiring" structures
>> Maybe a light dao layer or so might be handy in case you want to 
>> abstract away your persistence technology. At least you shouldn't 
>> query the DB directly in the UI Layer IMO.
> No need for that for us. KISS..Entities, when detached (after been 
> "loaded" in a  manager) are used like any other POJOs.. (almost)No 
> difference
If you have these "load methods" in your manager classes it is fine too, 
but be aware of the fact that the default behavior of EJB is to invoke 
any public method as if it was annotated with 
@TransactionAttribute(Required). If you for example put all your "load 
methods" into seperate SLSBs you only have to annotate the classes with 
@TransactionAttribute(Supports) to avoid starting a transaction every 
time such a method gets called. In contrast you would have to annotate 
each "load method" with @TransactionAttribute(Supports) to avoid 
transactions for these methods.
>>>
>>> I would love to see what Gavin King would answer to you on this..lol
>> About what exactly?
>>>
>>> Again I don't follow you in your answer (Usage of ConversationScope 
>>> etc..) vs my initial post
>> You wrote that it worked with the CDI conversation scope but not with 
>> the codi conversation scope.
> No I understand
> This is another post, Please comment in the other post.
> Thx
>>>
>>> Cheers
>>>
>>> Le 2012-12-12 17:28, Christian Beikov a écrit :
>>>> Why do you want to scope something that is stateless? I mean 
>>>> stateless already is some kind of scope, like pooled application 
>>>> scoped. Since you don't want to have a state in a stateless bean, 
>>>> why using a scope that will cause destroying the instance after 
>>>> conversation end?
>>>>
>>>> You should maybe consider using POJO beans scoped with whatever you 
>>>> want for your frontend(backing beans for views) and use something 
>>>> like application scope, singleton or stateless for your beans in 
>>>> the service layer.
>>>>
>>>> When this is about transaction handling, I can only recommend you 
>>>> to reconsider defining transactions in a service level but not in 
>>>> the UI layer. Transactions should also be as short as possible!
>>>>
>>>> Or is it maybe about entity managers being conversation scoped 
>>>> within the bean instances? In my opinion this is a bad and error 
>>>> prone practice. Keep your stuff as stateless as possible and use 
>>>> transaction scope.
>>>>
>>>> If you have no other choice than keeping on using these scopes for 
>>>> your beans you will probably have to tweak the class loader 
>>>> configuration as you already mentioned to make it working or 
>>>> consider using the javax.context.ConversationScoped annotation. 
>>>> Another option might also be to move the beans into the web 
>>>> application, but I am not sure if that will work 100% and I also 
>>>> discourage that.
>>>>
>>>> Mit freundlichen Grüßen,
>>>> ------------------------------------------------------------------------

>>>>
>>>> *Christian Beikov*
>>>> Am 12.12.2012 22:39, schrieb Denis Forveille:
>>>>> Bad news: In fact, in practice this does not work for us.
>>>>>
>>>>> We are moving from seam 2/jsf1.2  to cdi/jsf2.0/codi and we use SLSB
>>>>> (Stateless Session Beans) as JSF backing beans.
>>>>> Those SLSB may be of scope "ViewScope" (= Seam 2 "PageScope") and 
>>>>> need
>>>>> to be injected at leats "FacesContext" (to send back messages to the
>>>>> browser)
>>>>>
>>>>> So if we want to use the "@ViewAccessScoped" or "@ViewScope" and or
>>>>> other JSF artefacts (FacesMessages etc.) produced by CODI in our
>>>>> SLSBs, we need to have the codi-jsf jars visible in the classpath of
>>>>> the EJB module.
>>>>>
>>>>> The initial classloader problem with the jsf CODI jars in ear/lib
>>>>> comes because the JSF lifecycle uses JSF CODI classes loaded by
>>>>> another classloader than the one used by the WAR
>>>>>
>>>>> So if we want to setup our application as describes above with CODI,
>>>>> we have those options left:
>>>>> - configure the application classloader to "WAR classloader 
>>>>> policy" to
>>>>> "Application/single" instead of "Module/multiple" and put the CODI
>>>>> jars in ear/lib and keep PARENT_FIRST for both app and war. 
>>>>> Nothing in
>>>>> MANIFEST files (Tested OK.)
>>>>> - configure the application classloader to "WAR classloader 
>>>>> policy" to
>>>>> "Application/single" instead of "Module/multiple" and put the JSF 
>>>>> CODI
>>>>> jars at the root of the ear, put the rest of the CODI modules in
>>>>> ear/lib, keep PARENT_FIRST for both, add manifest entries for the WAR
>>>>> and EJB modules to the 2 CODI jsf jars (Tested OK)
>>>>>
>>>>> in brief we need to configure WebSphere to use only one classloader
>>>>> for the whole modules of the application (ejb+jpa+war+dependent jars)
>>>>>
>>>>>
>> <truncated>
>


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