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  2. JBRULES-3669

Bug when using two knowledge bases and one declarative model between



    • Type: Bug
    • Status: Resolved (View Workflow)
    • Priority: Major
    • Resolution: Rejected
    • Affects Version/s: 5.4.0.Final
    • Fix Version/s: None
    • Component/s: drools-compiler
    • Labels:


      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.

      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

      //DRL for resourceRules
      rule "Simple Rule"
      $entity: MyEntity()

      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();

      FactType factType = kbaseModel.getFactType("mymodel", "MyEntity");
      Object myEntity = factType.newInstance();
      factType.set(myEntity, "name", "Jackson Cunha Cassimiro");

      StatelessKnowledgeSession session = kbaseRules.newStatelessKnowledgeSession();

      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.

      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.

      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();




            mfusco Mario Fusco
            cereb Jackson Cunha (Inactive)
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