[rules-dev] [rules-users] class loading problems with 5.3.0-Final and 5.4.0-SNAPSHOT

[Mauricio Salatino]

We really need to analyze the difference and understand what is
happening under the hood.. because if not strange things can happen.
I will run the tests locally to see if I see something wrong.

Cheers

On Wed, Nov 16, 2011 at 5:46 PM, Mark Proctor <mproctor at codehaus.org> wrote:
> We original used classLoader.loadClass but then there was wierd bug with
> dynamic rules that wouldn't work, related to arrays. Switching to
> Class.forName avoided that bug. But I don't remember the exact details, it
> was several years ago now.
>
> Mark
>
> On Wed, Nov 16, 2011 at 5:50 PM, Mauricio Salatino <salaboy at gmail.com>
> wrote:
>>
>> Based on more tests and reading some articles about OSGI we (Professor
>> dotty and I) have found that
>> the composite class loader from drools is using Class.forName that is
>> being intercepted by the equinox OSGI container ->
>> at
>> org.eclipse.core.runtime.internal.adaptor.ContextFinder.loadClass(ContextFinder.java:124)
>> It looks like both are trying to load the same class definition and
>> the JVM throws the ClassCircularityError.
>> For my very basic example changing the CompositeClassLoader
>> implementation to use:
>>
>>                             cls = classLoader.loadClass(name);
>>
>> instead of:
>>                             cls = Class.forName( name,
>>                                                  resolve,
>>                                                  classLoader );
>> Fix the problems. But I'm not sure if that will work for all the other
>> cases.
>> Looking the usages of Class.forName inside compiler, core and api I
>> found that it is being used 39 times, which worries me.
>> I'm not planning to change all of them without being sure that is the
>> right way to go.  I will continue reading and testing to see if
>> changing the way of loading the classes is the only alternative.
>> Some notes about the difference between loadClass and forName:
>>
>> Classloader.loadClass() caches the loaded class object and returns
>> always the same class object
>>
>> This is done by the defining class loader
>> This ensures that each classloader loads the same class only once
>>
>> Class.forName() calls the normal classloader hierarchy to load the
>> class (same happens as above)
>>
>> But caches the class object within the initiating class loader
>> In standard cases no problem but can be tricky in dynamic environments
>>
>> Source
>> -> http://www.martinlippert.org/events/WJAX2008-ClassloadingTypeVisibilityOSGi.pdf
>> On Tue, Nov 15, 2011 at 4:04 PM, Davide Sottara <dsotty at gmail.com> wrote:
>> >
>> > Lovely exception...
>> > Well, both my life and salaboy's depend on solving this issue... Mark
>> > and I
>> > were also considering to review the Composite ClassLoader at some point
>> > in
>> > the future, since it causes issues with (re)declared types in DRLs
>> > loaded at
>> > runtime. Looks like we'll have to catch two birds with one stone :)
>> > Salaboy, can you share the simple service and the WSO2 config details?
>> > (version, any custom setting, etc...)
>> >
>> > --
>> > View this message in context:
>> > http://drools.46999.n3.nabble.com/rules-users-class-loading-problems-with-5-3-0-Final-and-5-4-0-SNAPSHOT-tp3509949p3510640.html
>> > Sent from the Drools: User forum mailing list archive at Nabble.com.
>> > _______________________________________________
>> > rules-users mailing list
>> > rules-users at lists.jboss.org
>> > https://lists.jboss.org/mailman/listinfo/rules-users
>>
>>
>>
>> --
>>  - CTO @ http://www.plugtree.com
>>  - MyJourney @ http://salaboy.wordpress.com
>>  - Co-Founder @ http://www.jugargentina.org
>>  - Co-Founder @ http://www.jbug.com.ar
>>
>>  - Salatino "Salaboy" Mauricio -
>>
>>
>>
>> --
>>  - CTO @ http://www.plugtree.com
>>  - MyJourney @ http://salaboy.wordpress.com
>>  - Co-Founder @ http://www.jugargentina.org
>>  - Co-Founder @ http://www.jbug.com.ar
>>
>>  - Salatino "Salaboy" Mauricio -
>>
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>
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-- 
 - CTO @ http://www.plugtree.com
 - MyJourney @ http://salaboy.wordpress.com
 - Co-Founder @ http://www.jugargentina.org
 - Co-Founder @ http://www.jbug.com.ar

 - Salatino "Salaboy" Mauricio -