[rules-users] IllegalAccessError in shadow classes
Godmar Back
godmar at gmail.com
Wed Feb 20 09:48:04 EST 2008
On Feb 20, 2008 9:23 AM, Edson Tirelli <tirelli at post.com> wrote:
>
> Godmar,
>
> Short answer: collection/maps objects are not javabeans.
>
Explain why this is a problem.
What is it about JavaBeans that your algorithm relies upon? Is it the
fact that the set of properties remains fixed and can be determined at
(fact) insertion time via reflection?
Otherwise, I do not see any conceptual difference between a map and a bean.
If that is the difference, then please allow maps with an immutable key set.
- Godmar
> Long answer: collection/maps must be shadowed to ensure consistency
> during execution, but how can we shadow the data if it is not exposed in a
> default, spec manner, as in javabeans? The algorithm we have in place right
> now is bellow. As you can see, it is a weak algo, but was the best I could
> come up at that time. If you have any suggestions on how to improve that, I
> appreciate.
>
> public Object getShadow(final Object fact) throws RuntimeDroolsException
> {
> ShadowProxy proxy = null;
> if ( isShadowEnabled() ) {
> try {
> if ( Collection.class.isAssignableFrom( this.shadowClass )
> || Map.class.isAssignableFrom( this.shadowClass ) ) {
> // if it is a collection, try to instantiate using
> constructor
> try {
> proxy = (ShadowProxy)
> this.shadowClass.getConstructor( new Class[]{cls} ).newInstance( new
> Object[]{fact} );
> } catch ( Exception e ) {
> // not possible to instantiate using constructor
> }
> }
> if ( proxy == null ) {
> if ( this.instantiator == null ) {
> this.setInstantiator();
> }
> proxy = (ShadowProxy) this.instantiator.newInstance();
> }
>
> proxy.setShadowedObject( fact );
> } catch ( final Exception e ) {
> System.out.println( "shadow: " +proxy.getClass() + ":" +
> fact.getClass() );
> throw new RuntimeDroolsException( "Error creating shadow
> fact for object: " + fact,
> e );
> }
> }
> return proxy;
>
>
> }
>
> []s
> Edson
>
> 2008/2/19, Godmar Back <godmar at gmail.com>:
> > 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
> > > _______________________________________________
> > > rules-users mailing list
> > > rules-users at lists.jboss.org
> > > https://lists.jboss.org/mailman/listinfo/rules-users
> > >
> > >
> > _______________________________________________
> > 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
> _______________________________________________
> rules-users mailing list
> rules-users at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
>
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