I'm migrating from an old Drools 5.1 version to 6.0.0.Final. Sometimes (I don't really get under which conditions as sometimes it works), I'm facing an InstantiationError exception when I insert a fact into a stateful kie session. This exception is thrown by a generated class named ConditionEvaluator<UUID> which doesn't help for debugging! The inserted object is a basic POJO (named JasmineEventEB) except for an attribute named "value" which accept any "Serializable" object and which is causing the issue. The rule condition is quite simple $e : JasmineEventEB(probe == "Button:pris" && value == "1") In debugging I found that it failed when evaluating the value == "1" part. I can also confirm that the value for the actually inserted JasmineEventEB is a string. The stacktrace is: java.lang.InstantiationError: java.io.Serializable at ConditionEvaluatorae1a73837e8146bda23004a0450e2e52.evaluate(Unknown Source) at org.drools.core.rule.constraint.MvelConstraint.evaluate(MvelConstraint.java:212) at org.drools.core.rule.constraint.MvelConstraint.isAllowed(MvelConstraint.java:169) at org.drools.core.reteoo.AlphaNode.assertObject(AlphaNode.java:134) at org.drools.core.reteoo.CompositeObjectSinkAdapter.doPropagateAssertObject(CompositeObjectSinkAdapter.java:502) at org.drools.core.reteoo.CompositeObjectSinkAdapter.propagateAssertObject(CompositeObjectSinkAdapter.java:387) at org.drools.core.reteoo.AlphaNode.assertObject(AlphaNode.java:138) at org.drools.core.reteoo.CompositeObjectSinkAdapter.doPropagateAssertObject(CompositeObjectSinkAdapter.java:502) at org.drools.core.reteoo.CompositeObjectSinkAdapter.propagateAssertObject(CompositeObjectSinkAdapter.java:377) at org.drools.core.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:288) at org.drools.core.reteoo.EntryPointNode.assertObject(EntryPointNode.java:260) at org.drools.core.common.NamedEntryPoint.insert(NamedEntryPoint.java:360) at org.drools.core.common.NamedEntryPoint.insert(NamedEntryPoint.java:279) at org.drools.core.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:1149) at org.drools.core.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:1093) at org.drools.core.impl.StatefulKnowledgeSessionImpl.insert(StatefulKnowledgeSessionImpl.java:308)
Fixed by https://github.com/droolsjbpm/drools/commit/d198e3a696f02863a1bb4d184d5e01ed9739ea37
Verified in BRMS 6.0.1-redhat-2