[rules-users] IllegalAccessError in shadow classes

[Godmar Back]

As a general comment, the examples for which I find Drools failing are
not the actual examples for which my application is failing. It's just
the smallest test case I was able to eliminate.

I'm now a bit concerned about your comment that Maps and Collections
aren't well-defined as Facts. I am planning to make extensive use of
them (that's also why I'd prefer to use the MVEL dialect, because in
Java I cannot do this without creating Bean wrappers.)

Could you elaborate what makes the semantics not "well-defined".

I'm specifically concerned with immutable maps (such as the one that
would have been returned by Collections.singletonMap), and with
collections of maps (such as those obtained via a "from"..." clause).
I need to insert immutable maps as facts; I understand that the items
returned by "from" aren't inserted as facts.

 - Godmar

On Feb 19, 2008 3:11 PM, Edson Tirelli <tirelli at post.com> wrote:
>
>    Drools tries to create the ShadowProxy. The reason is that it does not
> know about the implementation... it just knows it is a Map and as so, it
> must be shadowed. Problem is that SingletonMap is either  final or does not
> have a default constructor.
>     My recommendation, besides opening a JIRA for this, is avoid inserting
> collections/maps directly as facts. The semantic for such facts is not
> clearly defined and it may cause undesired behavior.
>
>    []s
>    Edson
>
> 2008/2/19, Godmar Back <godmar at gmail.com>:
> >
> >
> >
> > Hi,
> >
> > usings Drools 4.0.4 and MVEL 1.4, this simple rule:
> > ---
> > package test;
> >
> > import java.util.Collections;
> >
> > dialect "mvel"
> >
> > rule "Rule #1"
> > when
> > then
> >     insert(Collections.singletonMap("content", "hello"));
> > end
> > --
> >
> > produces:
> > java.lang.IllegalAccessError: class
> > org.drools.shadow.java.util.Collections$SingletonMapShadowProxy cannot
> > access its superclass java.util.Collections$SingletonMap
> >         at java.lang.ClassLoader.defineClass1(Native Method)
> >         at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
> >         at
> org.drools.rule.MapBackedClassLoader.fastFindClass(MapBackedClassLoader.java:60)
> >         at
> org.drools.rule.MapBackedClassLoader.loadClass(MapBackedClassLoader.java:79)
> >         at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
> >         at
> org.drools.reteoo.Rete$ClassObjectTypeConf.loadOrGenerateProxy(Rete.java:547)
> >         at
> org.drools.reteoo.Rete$ClassObjectTypeConf.defineShadowProxyData(Rete.java:494)
> >         at
> org.drools.reteoo.Rete$ClassObjectTypeConf.<init>(Rete.java:461)
> >         at org.drools.reteoo.Rete.assertObject(Rete.java:152)
> >         at
> org.drools.reteoo.ReteooRuleBase.assertObject(ReteooRuleBase.java:192)
> >         at
> org.drools.reteoo.ReteooWorkingMemory.doInsert(ReteooWorkingMemory.java:71)
> >         at
> org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:909)
> >         at
> org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:881)
> >         at
> org.drools.base.DefaultKnowledgeHelper.insert(DefaultKnowledgeHelper.java:67)
> >         at
> org.drools.base.DefaultKnowledgeHelper.insert(DefaultKnowledgeHelper.java:61)
> >
> >
> > It's not clear to me why Drools creates Proxies for such classes as
> > java.util.Collections, or does MVEL do it?
> >
> > - Godmar
> > _______________________________________________
> > rules-users mailing list
> > rules-users at lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/rules-users
> >
>
>
>
> --
>   Edson Tirelli
>   JBoss Drools Core Development
>    Office: +55 11 3529-6000
>   Mobile: +55 11 9287-5646
>   JBoss, a division of Red Hat @ www.jboss.com
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>