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

[Mauricio Salatino]

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.
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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 -



-- 
 - 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 -