[jboss-jira] [JBoss JIRA] (JBRULES-3669) Bug when using two knowledge bases and one declarative model between

[Davide Sottara (JIRA)]

    [ https://issues.jboss.org/browse/JBRULES-3669?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12729587#comment-12729587 ] 

Davide Sottara commented on JBRULES-3669:
-----------------------------------------

This might be a critical bug, or not a bug at all, I'd like to hear other opinions...

The issue is that you are building the knowledege base incrementally. The second knowledge builder, then, needs to share the same classloader as the first. To do this, you correctly
pass the KnowledgeBase to the second KnowledgeBuilder. Now, this would be enough: kbuilderRules will apply the changes directly into the existing knowledgebase. In this case, there is
no need to create a second knowledge base.

If you wanted to create a second knowledge base, you will have to share the first knowledge base's classloader:

KnowledgeBaseConfiguration kbConf = KnowledgeBaseFactory.newKnowledgeBaseConfiguration(
                null, 
                ((ReteooRuleBase)((KnowledgeBaseImpl) kbaseModel).getRuleBase()).getRootClassLoader() );
KnowledgeBase kbaseRules = KnowledgeBaseFactory.newKnowledgeBase( kbConf );

I agree that this sequence of casts is not immediate, but the knowledge base configuration and the package building process is being rewritten in 6.0 anyway. 
Also consider that the KnowledgeAgent is (supposedly) the recommended way of managing incremental KBs in 5.x

Best
Davide

Oh, btw, you are missing a ";" in the rule, but this might be a cut&paste typo :)
                
> Bug when using two knowledge bases and one declarative model between
> --------------------------------------------------------------------
>
>                 Key: JBRULES-3669
>                 URL: https://issues.jboss.org/browse/JBRULES-3669
>             Project: Drools
>          Issue Type: Bug
>      Security Level: Public(Everyone can see) 
>          Components: drools-compiler
>    Affects Versions: 5.4.0.Final
>            Reporter: Jackson Cunha
>            Assignee: Mark Proctor
>
> Hello conrads.
> To explain what I need, the problem that I found and the solution that I planning to use, I will firstly describe my cenario.
> Cenario
> In my cenario, I have a declarative model and rules of different groups. I need put each rules group in a different knowledge base and all of it will share the same declarative model.
> In a time, I will create a fact using fact types defined in a knowledge base that I will call as kbaseModel. This knowledge base will have only the declarative model and no rules.
> All facts created will be used in other knowledge base, called kbaseRules. All kbaseRules have only rules and no declarative model, because model was defined in kbaseModel.
> I could have many kbaseRules but exists only one kbaseModel.
> Using the Drools API, teoricaly, I could implement my cenario using the following code:
> //DRL for resourceModel
> declare MyEntity
>    name : String
> end
> //DRL for resourceRules
> rule "Simple Rule"
>    when
>       $entity: MyEntity()
>    then
>       System.out.println($entity)
>    end
> Resource resourceModel = ... //Resource with only the declarative model and no rules
> Resource resourceRules = ... //Resource with only rules and no declarative model
> KnowledgeBuilder kbuilderModel = KnowledgeBuilderFactory.newKnowledgeBuilder();
> kbuilderModel add(resourceModel, ResourceType.DRL);
> KnowledgeBase kbaseModel = kbuilderModel.newKnowledgeBase();
> KnowledgeBuilder kbuilderRules = KnowledgeBuilderFactory.newKnowledgeBuilder(kbaseModel);
> kbuilderRules.add(resourceRules, ResourceType.DRL);
> KnowledgeBase kbaseRules = KnowledgeBaseFactory.newKnowledgeBase();
> kbaseRules.addKnowledgePackages(kbuilderRules.getKnowledgePackages());
> FactType factType = kbaseModel.getFactType("mymodel", "MyEntity");
> Object myEntity = factType.newInstance();
> factType.set(myEntity, "name", "Jackson Cunha Cassimiro");
> StatelessKnowledgeSession session = kbaseRules.newStatelessKnowledgeSession();
> session.execute(myEntity);
> This code should work, but when I try to run I get this stacktrace:
> java.lang.ClassNotFoundException: Unable to load class: mymodel.MyEntity
>    at org.drools.util.CompositeClassLoader.loadClass(CompositeClassLoader.java:92)
>    at org.drools.common.AbstractRuleBase.registerAndLoadTypeDefinition(AbstractRuleBase.java:649)
>    at org.drools.common.AbstractRuleBase.addPackages(AbstractRuleBase.java:553)
>    at org.drools.reteoo.ReteooRuleBase.addPackages(ReteooRuleBase.java:472)
>    at org.drools.impl.KnowledgeBaseImpl.addKnowledgePackages(KnowledgeBaseImpl.java:150)
>    at app.UsingDeclares.main(UsingDeclares.java:79)
> Exception in thread "main" org.drools.RuntimeDroolsException: unable to resolve Type Declaration class 'mymodel.MyEntity'
>    at org.drools.common.AbstractRuleBase.addPackages(AbstractRuleBase.java:582)
>    at org.drools.reteoo.ReteooRuleBase.addPackages(ReteooRuleBase.java:472)
>    at org.drools.impl.KnowledgeBaseImpl.addKnowledgePackages(KnowledgeBaseImpl.java:150)
>    at app.UsingDeclares.main(UsingDeclares.java:79)
> It happens because Drools can't find any reference of mymodel.MyEntity in kbaseRules, but this kbase was built from kbaseModel that already have this class declared. I think it can be a bug.
> Debuging
> During creation of kbaseModel, a method called mergePackage(pkgRegistry, packageDescr) from PackageBuilder class is invoked. The pkgRegistry not contains any reference to declarative model. The packageDescr contains a list of type definitions from declarative model. Inside mergePackage is invoked other method, called processTypeDeclarations(pkgRegistry, packageDescr) that will iterate over all type definitions from packageDescr and will fill a map called Map<String,byte[]> classLookups from JavaDialectRuntimeData class.
> During the creation of kbaseRules the method mergePackage(pkgRegistry, packageDescr) from PackageBuilder is invoked again, but at this time pkgRegistry contains all type definitions defined previously in kbaseModel and packageDescr not contains any type definitions, only rules. When the method processTypeDeclarations(pkgRegistry, packageDescr) from PackageBuilder is called and try iterate over type definitions of packageDescr, this is empty and nothing is done and the map Map<String,byte[]> classLookups from JavaDialectRuntimeData will be empty too.
> The classLookups empty is the cause of ClassNotFoundException.
> Solution
> The solution that I found was apply reflection to fill Map<String,byte[]> classLookups from JavaDialectRuntimeData correctly before add the packages into kbaseRules: 
> Collection<KnowledgePackage> packages = kbuilderRules.getKnowledgePackages();
> Mirror mirror = new Mirror();//Reflection utilities
> 		
> for (KnowledgePackage kPackage : packages) {
>    Package pkg =  (Package) mirror.on(kPackage).get().field("pkg");
>    JavaDialectRuntimeData dialect = (JavaDialectRuntimeData) pkg.getDialectRuntimeRegistry().getDialectData( "java" );
> 			
>    for (FactType factType : kPackage.getFactTypes()) {
>       Class<?> c = factType.getFactClass();
>       String className = c.getName();
>       String classAsPath = className.replace('.', '/') + ".class";
>       InputStream stream = c.getClassLoader().getResourceAsStream(classAsPath);
>       byte[] bytes = IOUtils.toByteArray(stream);
>       dialect.putClassDefinition(classAsPath, bytes);
>    }
> }
> KnowledgeBase kbaseRules = KnowledgeBaseFactory.newKnowledgeBase();
> kbaseRules.addKnowledgePackages(packages);

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