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From "Sergey Beryozkin" <sbery...@progress.com>
Subject Re: ProviderFactory singleton?
Date Mon, 09 Mar 2009 10:37:56 GMT
Hi,

I wish someone explained me why things will get worse in OSGI, with ProviderFactory.getInstance().
There's a direct relationship between any given endpoint and a ProviderFactory instance and
ProviderFactory does not rely itself on some FactoryFinders, etc...It's all quite straightforward
really there and  at the moment I don't see why things will fail in OSGI, given that in fact
I've seen CXF JAXRS working in OSGI, though withougt multiple endpoints being involved.
Is it because ProviderFactory has static fields ? Are we talking here about multiple CXF JAXRS
bundles being loaded ? I guess we will have multiple versions in this case so I don't see
why classloading issues will arise in such cases. What is it that I'm missing ? It simply
encapsulates the requirement "try user providers first, delegate to the defulat ones as the
last resort". 

> Each module has no knowledge of any other module its deployed next to, which is why multiple
modules may easily have overlapping addresses.

this is more intertesting to me really, as it's about the concrete problem which might occur
at the deployment time. I honestly did not know that it were possible to have multiple jaxrs:endpoints
with identical address values working even only with default providers involved (note, overlapping
addresses, as in say '/bar' and '/' should work fine with per-endpoint providers), with CXF
servlets providing the needed uniqueness to the actual adresses. I'll need to think how it
can be accomodated - I'm just not sure yet how :-). Perhaps the validation rules invoked at
the deployment time would ensure the uniqueness of jaxrs:endpoint addresses - but that depends
on the availability of such rules - and again - if things are expected to work with multiple
endpoints having identical @adress values then CXF JAXRS has to ensure per-endpoint providers
don't clash with eath other. 

thanks, Sergey  




> On Fri March 6 2009 7:12:51 am Sergey Beryozkin wrote:
>>
>> One issue is that ProviderFactory is also used at the moment in the
>> client api,
> 
> Doesn't the Client API also use the Bus?   Could/Should it?   (example: does 
> it currently use the HTTPConduit/transport?)   If so, hanging this off the bus 
> is probably the best idea.    I definitely agree that Singletons are a really 
> bad idea.   It actually will get worse with OSGi as classloaders and stuff are 
> different so that singleton could end up holding onto things and exposing 
> things from other applications. 
> 
> Dan
> 
> 
>> though an endpoint info representation is also created
>> there. So we might in principle have a thread local endpoint info
>> storage, such that ProviderFactory.getInstance() would use thread-local
>> endpoint info as a key to get the actual ProviderFactory instance.
>> Perhaps a simpler option is to just keep a ProviderFactory instance with
>> a given Endpoint. I need to think about it - it's getting a bit tight
>> now, as 2.2 is likely to go out quite soon so such a change may not make
>> it into the trunk say next week...
>>
>> But do you think the possible update as suggested above would not be
>> quite acceptable in your case, even as a workaround? I'd like to
>> understand better when it may be unrealistic to ensure that different
>> endpoints have their own addresses : perhaps there're policies on which
>> uri patterns go to web.xml or to resource classes, etc ?
>>
>> Cheers, Sergey
>>
>>
>>
>> -----Original Message-----
>> From: Tong, Gary (IDEAS) [mailto:Gary.Tong@morganstanley.com]
>> Sent: 06 March 2009 11:44
>> To: dev@cxf.apache.org
>> Subject: RE: ProviderFactory singleton?
>>
>> > Is it when you have multiple CXF servlets, each of them referencing
>>
>> different spring configuration files ?
>>
>> Yes exactly.
>>
>> -----Original Message-----
>> From: Sergey Beryozkin [mailto:sberyozk@progress.com]
>> Sent: 06 March 2009 10:18
>> To: dev@cxf.apache.org
>> Subject: RE: ProviderFactory singleton?
>>
>> Hi Gary
>>
>> I've updated a bit ProviderFactory on the trunk, there's a default
>> ProviderFactory which hosts the default providers and a ProviderFactory
>> instance per every endpoint address, for ex,
>> ProviderFactory.getInstance() and ProviderFactory.getInstance("/") would
>> return an instance keyed by '/', etc.
>> So I thought that an endpoint address, as specified by jaxrs:endpoint,
>> would be a unique enough key for ProviderFactory instances.
>>
>> Do you have the case where multiple endpoints share the same
>> jaxrs:endpoint/@address ?
>>
>> Is it when you have multiple CXF servlets, each of them referencing
>> different spring configuration files ?
>>
>> Cheers, Sergey
>>
>> -----Original Message-----
>> From: Tong, Gary (IDEAS) [mailto:Gary.Tong@morganstanley.com]
>> Sent: 06 March 2009 09:14
>> To: dev@cxf.apache.org
>> Subject: ProviderFactory singleton?
>>
>> Been looking through the code, and why is ProviderFactory a singleton?
>> I would think it would be tied to a bus or a server.  It differentiates
>> by address, but currently I'm working on something with two side-by-side
>> CXF servlets that load completely different CXF configurations.  In this
>> case, providers declared in one server are bleeding into the other
>> because the ProviderFactory uses a singleton.
>>
>> Worth fixing?  Also, are there any other uses of singletons in the
>> system that maybe should be looked at?
>>
>> Cheers,
>> Gary
>>
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> 
> -- 
> Daniel Kulp
> dkulp@apache.org
> http://www.dankulp.com/blog
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