[rules-users] [rules-dev] 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...)
>
> --
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> Sent from the Drools: User forum mailing list archive at Nabble.com.
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 - Salatino "Salaboy" Mauricio -
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