<br> Godmar,<br><br> Short answer: collection/maps objects are not javabeans.<br><br> 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.<br>
<br> public Object getShadow(final Object fact) throws RuntimeDroolsException {<br> ShadowProxy proxy = null;<br> if ( isShadowEnabled() ) {<br> try {<br> if ( Collection.class.isAssignableFrom( this.shadowClass ) || Map.class.isAssignableFrom( this.shadowClass ) ) {<br>
// if it is a collection, try to instantiate using constructor<br> try {<br> proxy = (ShadowProxy) this.shadowClass.getConstructor( new Class[]{cls} ).newInstance( new Object[]{fact} );<br>
} catch ( Exception e ) {<br> // not possible to instantiate using constructor<br> }<br> }<br> if ( proxy == null ) {<br> if ( this.instantiator == null ) {<br>
this.setInstantiator();<br> }<br> proxy = (ShadowProxy) this.instantiator.newInstance();<br> }<br> <br> proxy.setShadowedObject( fact );<br>
} catch ( final Exception e ) {<br> System.out.println( "shadow: " +proxy.getClass() + ":" + fact.getClass() );<br> throw new RuntimeDroolsException( "Error creating shadow fact for object: " + fact,<br>
e );<br> }<br> }<br> return proxy;<br> }<br><br> []s<br> Edson<br><br><div><span class="gmail_quote">2008/2/19, Godmar Back <<a href="mailto:godmar@gmail.com">godmar@gmail.com</a>>:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
As a general comment, the examples for which I find Drools failing are<br>not the actual examples for which my application is failing. It's just<br>the smallest test case I was able to eliminate.<br><br>I'm now a bit concerned about your comment that Maps and Collections<br>
aren't well-defined as Facts. I am planning to make extensive use of<br>them (that's also why I'd prefer to use the MVEL dialect, because in<br>Java I cannot do this without creating Bean wrappers.)<br><br>Could you elaborate what makes the semantics not "well-defined".<br>
<br>I'm specifically concerned with immutable maps (such as the one that<br>would have been returned by Collections.singletonMap), and with<br>collections of maps (such as those obtained via a "from"..." clause).<br>
I need to insert immutable maps as facts; I understand that the items<br>returned by "from" aren't inserted as facts.<br><br> - Godmar<br><br>On Feb 19, 2008 3:11 PM, Edson Tirelli <<a href="mailto:tirelli@post.com">tirelli@post.com</a>> wrote:<br>
><br>> Drools tries to create the ShadowProxy. The reason is that it does not<br>> know about the implementation... it just knows it is a Map and as so, it<br>> must be shadowed. Problem is that SingletonMap is either final or does not<br>
> have a default constructor.<br>> My recommendation, besides opening a JIRA for this, is avoid inserting<br>> collections/maps directly as facts. The semantic for such facts is not<br>> clearly defined and it may cause undesired behavior.<br>
><br>> []s<br>> Edson<br>><br>> 2008/2/19, Godmar Back <<a href="mailto:godmar@gmail.com">godmar@gmail.com</a>>:<br>> ><br>> ><br>> ><br>> > Hi,<br>> ><br>> > usings Drools 4.0.4 and MVEL 1.4, this simple rule:<br>
> > ---<br>> > package test;<br>> ><br>> > import java.util.Collections;<br>> ><br>> > dialect "mvel"<br>> ><br>> > rule "Rule #1"<br>> > when<br>> > then<br>
> > insert(Collections.singletonMap("content", "hello"));<br>> > end<br>> > --<br>> ><br>> > produces:<br>> > java.lang.IllegalAccessError: class<br>> > org.drools.shadow.java.util.Collections$SingletonMapShadowProxy cannot<br>
> > access its superclass java.util.Collections$SingletonMap<br>> > at java.lang.ClassLoader.defineClass1(Native Method)<br>> > at java.lang.ClassLoader.defineClass(ClassLoader.java:620)<br>
> > at<br>> org.drools.rule.MapBackedClassLoader.fastFindClass(MapBackedClassLoader.java:60)<br>> > at<br>> org.drools.rule.MapBackedClassLoader.loadClass(MapBackedClassLoader.java:79)<br>
> > at java.lang.ClassLoader.loadClass(ClassLoader.java:251)<br>> > at<br>> org.drools.reteoo.Rete$ClassObjectTypeConf.loadOrGenerateProxy(Rete.java:547)<br>> > at<br>> org.drools.reteoo.Rete$ClassObjectTypeConf.defineShadowProxyData(Rete.java:494)<br>
> > at<br>> org.drools.reteoo.Rete$ClassObjectTypeConf.<init>(Rete.java:461)<br>> > at org.drools.reteoo.Rete.assertObject(Rete.java:152)<br>> > at<br>> org.drools.reteoo.ReteooRuleBase.assertObject(ReteooRuleBase.java:192)<br>
> > at<br>> org.drools.reteoo.ReteooWorkingMemory.doInsert(ReteooWorkingMemory.java:71)<br>> > at<br>> org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:909)<br>> > at<br>
> org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:881)<br>> > at<br>> org.drools.base.DefaultKnowledgeHelper.insert(DefaultKnowledgeHelper.java:67)<br>> > at<br>
> org.drools.base.DefaultKnowledgeHelper.insert(DefaultKnowledgeHelper.java:61)<br>> ><br>> ><br>> > It's not clear to me why Drools creates Proxies for such classes as<br>> > java.util.Collections, or does MVEL do it?<br>
> ><br>> > - Godmar<br>> > _______________________________________________<br>> > rules-users mailing list<br>> > <a href="mailto:rules-users@lists.jboss.org">rules-users@lists.jboss.org</a><br>
> > <a href="https://lists.jboss.org/mailman/listinfo/rules-users">https://lists.jboss.org/mailman/listinfo/rules-users</a><br>> ><br>><br>><br>><br>> --<br>> Edson Tirelli<br>> JBoss Drools Core Development<br>
> Office: +55 11 3529-6000<br>> Mobile: +55 11 9287-5646<br>> JBoss, a division of Red Hat @ <a href="http://www.jboss.com">www.jboss.com</a><br>> _______________________________________________<br>> rules-users mailing list<br>
> <a href="mailto:rules-users@lists.jboss.org">rules-users@lists.jboss.org</a><br>> <a href="https://lists.jboss.org/mailman/listinfo/rules-users">https://lists.jboss.org/mailman/listinfo/rules-users</a><br>><br>
><br>_______________________________________________<br>rules-users mailing list<br><a href="mailto:rules-users@lists.jboss.org">rules-users@lists.jboss.org</a><br><a href="https://lists.jboss.org/mailman/listinfo/rules-users">https://lists.jboss.org/mailman/listinfo/rules-users</a><br>
</blockquote></div><br><br clear="all"><br>-- <br> Edson Tirelli<br> JBoss Drools Core Development<br> Office: +55 11 3529-6000<br> Mobile: +55 11 9287-5646<br> JBoss, a division of Red Hat @ <a href="http://www.jboss.com">www.jboss.com</a>