KnowledgeAgent custom class loader not working for PKG resources

Wednesday, 15 February 2012

I believe there may be a bug when trying to use a custom class loader with
the KnowledgeAgent and the KnowledgeBuilderConfiguration, and when the
ChangeSet is a PKG resource. 

I have been trying to get the knowledge-agent-classloader sample from the
new Drools Cookbook to work with a PKG resource.  The sample works fine for
a DRL resource, but when I convert it to use my fact jar, and a PKG resource
containing my rules, which I downloaded from Guvnor, it throws a
ClassNotFoundException for my fact model.  If I put my fact model in the
classpath, the error goes away and my rules can be added to the
KnowledgeAgent and run correctly.  Following is the code from the sample
that I have converted, and I have attached a zip file with a complete
project demonstrating the problem.  Also,  I  can get my rules and fact
model to work if I use a DRL ChangeSet.knowledge-agent-classloader.zip

  URL modelJarURL = getClass().getResource("Patient-1.0.jar"); 

        URLClassLoader customURLClassloader = new URLClassLoader(new URL[]
{modelJarURL }); 

        KnowledgeBuilderConfiguration kbuilderConfig =
KnowledgeBuilderFactory.newKnowledgeBuilderConfiguration(null, 
                customURLClassloader); 

        KnowledgeBaseConfiguration kbaseConfig =
KnowledgeBaseFactory.newKnowledgeBaseConfiguration(null,
customURLClassloader); 
        KnowledgeBase kbase =
KnowledgeBaseFactory.newKnowledgeBase(kbaseConfig); 

        KnowledgeAgentConfiguration aconf =
KnowledgeAgentFactory.newKnowledgeAgentConfiguration(); 
        KnowledgeAgent kagent =
KnowledgeAgentFactory.newKnowledgeAgent("test", kbase, aconf,
kbuilderConfig); 

        // kagent.applyChangeSet(new ClassPathResource("change-set.xml",
getClass())); // this goes with model.jar 
        // kagent.applyChangeSet(new ClassPathResource("drl-change-set.xml",
getClass())); // this goes with Patient.jar 
        kagent.applyChangeSet(new ClassPathResource("pkg-change-set.xml",
getClass())); // this goes with Patient.jar 

        return kagent.getKnowledgeBase(); 

Following is the stack trace from the error: 

java.lang.NullPointerException 
        at
org.drools.impl.KnowledgeBaseImpl.addKnowledgePackages(KnowledgeBaseImpl.java:148) 
        at
org.drools.agent.impl.KnowledgeAgentImpl.addResourcesToKnowledgeBase(KnowledgeAgentImpl.java:1016)

        at
org.drools.agent.impl.KnowledgeAgentImpl.rebuildResources(KnowledgeAgentImpl.java:785) 
        at
org.drools.agent.impl.KnowledgeAgentImpl.buildKnowledgeBase(KnowledgeAgentImpl.java:657) 
        at
org.drools.agent.impl.KnowledgeAgentImpl.applyChangeSet(KnowledgeAgentImpl.java:190) 
        at
org.drools.agent.impl.KnowledgeAgentImpl.applyChangeSet(KnowledgeAgentImpl.java:169) 
        at
drools.cookbook.chapter02.KnowledgeAgentClassloaderTest.createKnowledgeBase(KnowledgeAgentClassloaderTest.java:59)
        at
drools.cookbook.chapter02.KnowledgeAgentClassloaderTest.customClassloaderTest(KnowledgeAgentClassloaderTest.java:30)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) 
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
        at java.lang.reflect.Method.invoke(Unknown Source) 
        at org.junit.internal.runners.TestMethod.invoke(TestMethod.java:59) 
        at
org.junit.internal.runners.MethodRoadie.runTestMethod(MethodRoadie.java:98) 
        at
org.junit.internal.runners.MethodRoadie$2.run(MethodRoadie.java:79) 
        at
org.junit.internal.runners.MethodRoadie.runBeforesThenTestThenAfters(MethodRoadie.java:87)

        at
org.junit.internal.runners.MethodRoadie.runTest(MethodRoadie.java:77) 
        at org.junit.internal.runners.MethodRoadie.run(MethodRoadie.java:42) 
        at
org.junit.internal.runners.JUnit4ClassRunner.invokeTestMethod(JUnit4ClassRunner.java:88) 
        at
org.junit.internal.runners.JUnit4ClassRunner.runMethods(JUnit4ClassRunner.java:51) 
        at
org.junit.internal.runners.JUnit4ClassRunner$1.run(JUnit4ClassRunner.java:44) 
        at
org.junit.internal.runners.ClassRoadie.runUnprotected(ClassRoadie.java:27) 
        at
org.junit.internal.runners.ClassRoadie.runProtected(ClassRoadie.java:37) 
        at
org.junit.internal.runners.JUnit4ClassRunner.run(JUnit4ClassRunner.java:42) 
        at
org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)

        at
org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) 
        at
org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)

        at
org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)

        at
org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390) 
        at
org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197) 

I have been having the exact same problem when trying to use a custom class
loader with just a KnowldegeBuilder and no KnowledgeAgent.   
http://drools.46999.n3.nabble.com/file/n3746456/knowledge-agent-classload...
knowledge-agent-classloader.zip 

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