[rules-users] drools 6 and osgi

Fri Jun 21 19:30:00 EDT 2013

On 21 Jun 2013, at 23:21, Florian.Pirchner <florian.pirchner at gmail.com> wrote:

> hi cristiano,
> 
> yep. class#forname is just one issue.
> i agree that the modularity issue is an important one too.
> 
> to provide a framework for non osgi and osgi environments is really a challenge. my prefered way would be the use of osgi services to avoid the classloading issues. so the problems with dependencies would not influence the system. only api is required as import package. the impl is invisible for the consumer.
> but for now i have no idea how a proper implementation could look like.  
> 
> peter kriens suggested the use of http://code.google.com/p/pojosr/ to build an osgi like system in non osgi environments.
> but never used it. and i also do not know whether it might help with osgi integration. does anybody have experience with pojosr?
> 
> @mark: what are your current ideas about integrating osgi properly?
We do work on it, as and when we can. 	My team and I's time is limited on this, there isn't a demand for OSGi from paying customers. So this is mostly a best effort, combined with what ever the community can help on.

Mark
> 
> best florian
> 
> Am 21.06.2013 um 23:49 schrieb Cristiano Gavião <cvgaviao at gmail.com>:
> 
>> Florian,
>> 
>> Don't think that the problem that we are facing in Drools6 is because the Class.forName on its own. 
>> 
>> But the problem is from which bundle it is being called and where resides the class that it is trying to load...
>> 
>> Definitively one bundle CAN'T load classes that resides in another bundle, unless you specify a import of the package... That is why currently kie-api has an import to org.drools.compiler.kie.builder.impl 
>> 
>> so the solution must be composed by two steps: Repackage some classes, so a class will be loaded by its own bundle and use services... 
>> 
>> On 21/06/13 03:30, Florian Pirchner wrote:
>>> Hi Mark,
>>> 
>>> i did some research. Indeed a very complex issue.
>>> Tried to find out the difference about Class.forName(String) and Class.forName(String, boolean, ClassLoader). Both of them are delegating to native jvm methods and the difference seems to be in resolving the class and the way that caches work.
>>> 
>>> In http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6500212 they are pointing to use Class.forName(String, boolean, ClassLoader). Could find that method call in some drools and jbpm classes. For instance compiler...
>>> 
>>> But there are also a lot of Class.forName(String) calls too. Specialy in parts of code where no array-types come into play.
>>> For instance JavaHandlerWorkItemHandler calls  (Class<JavaHandler>) Class.forName(className).
>>> 
>>> Maybe it would be a good idea to replace Class.forName() for issues that exclude array-types by classloader.loadClass().
>>> 
>>> WDYT?
>>> 
>>> Best Florian
>>> 
>>> 
>>> 
>>> Am 20.06.13 17:28, schrieb Mark Proctor:
>>>> There are bugs with loadClass and serialisation :(
>>>> http://lists.jboss.org/pipermail/rules-dev/2011-November/003681.html
>>>> 
>>>> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6500212
>>>> "Thus, we highly recommend replacement of this
>>>>             code:
>>>>   myClassLoader.loadClass(className);
>>>> 
>>>> With this code:
>>>> 
>>>>   Class.forName(className,false,myClassLoader);"
>>>> 
>>>> Mark
>>>> On 20 Jun 2013, at 15:01, Florian Pirchner <florian.pirchner at gmail.com> wrote:
>>>> 
>>>>> Hi,
>>>>> 
>>>>> i also saw all the Class.forName. Class.forName additionally uses a very 
>>>>> aggressive class caching policy.
>>>>> See here:
>>>>> http://blog.osgi.org/2011/05/what-you-should-know-about-class.html
>>>>> http://blog.bjhargrave.com/2007/09/classforname-caches-defined-class-in.html
>>>>> 
>>>>> I do not understand why API imports compiler.impl? Maybe to enable 
>>>>> class#forname i guess.
>>>>> 
>>>>> 
>>>>> Is there an intention to use a more modularized way in v6 beta4 when 
>>>>> OSGi support will be implemented?
>>>>> 
>>>>> Thanks Florian
>>>>> 
>>>>> 
>>>>> Am 20.06.13 15:43, schrieb Cristiano Gavião:
>>>>>> Hi,
>>>>>> 
>>>>>> Well, besides the fact that the services that we used on version 5.x is
>>>>>> still there, I'm not that optimist with Drools 6 running well in an OSGi
>>>>>> container... at least not currently...
>>>>>> 
>>>>>> Last week I played a bit too with Jbosgi and Wildfly and got a lot of
>>>>>> classloading errors due some factory classes trying to load classes that
>>>>>> are in another bundles...
>>>>>> 
>>>>>> what surprise me most was that kie-api has an import to
>>>>>> org.drools.compiler.kie.builder.impl ! :)
>>>>>> 
>>>>>> regards,
>>>>>> 
>>>>>> John
>>>>>> On 17/06/13 19:39, Florian.Pirchner wrote:
>>>>>>> hi,
>>>>>>> 
>>>>>>> i got a question about osgi support.
>>>>>>> is beta 3 already useable in osgi environments? could see that activators are registering v5 api as services.
>>>>>>> 
>>>>>>> is it possible to consume osgi services in the script tasks and rules by context? is this planned for version 6? would be a great feature.
>>>>>>> 
>>>>>>> thanks a lot for answer
>>>>>>> florian
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>>>>> 
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>>>> 
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>>> 
>>> -- 
>>> Mit besten Grüßen
>>> Florian Pirchner
>>> Fohlenweg 22
>>> 2301 Probstdorf
>>> Tel: +43 650 7772338
>>> florian.pirchner at gmail.com
>>> 
>>> 
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