Drools java.lang.NullPointerException at org.drools.reteoo.RuleTerminalNode 任何想法

Question

这些天我和往常一样努力流口水。老实说，我有很多困难，我有点灰心。现在我有这个问题。 我的应用程序必须监视磁接触何时被激活，以及接触释放事件何时必须被撤回。反之亦然。这是我的规则和我拥有的大空指针。任何帮助将不胜感激！非常感谢！

 rule "contact activated vs contact released"   salience 0 no-loop true
    when
        $contact_activated : Event(type == EventType.CONTACT_ACTIVATED) ||  

    $contact_released : Event(type == EventType.CONTACT_RELEASED)
        then

             if($contact_activated!= null) {
                retract($contact_activated);
             } else {
                retract($contact_released);
             }
end 

和 我有

java.lang.NullPointerException
    at org.drools.reteoo.RuleTerminalNode$SortDeclarations.compare(RuleTerminalNode.java:477)
    at org.drools.reteoo.RuleTerminalNode$SortDeclarations.compare(RuleTerminalNode.java:473)
    at java.util.Arrays.mergeSort(Arrays.java:1270)
    at java.util.Arrays.sort(Arrays.java:1210)
    at org.drools.reteoo.RuleTerminalNode.<init>(RuleTerminalNode.java:119)
    at org.drools.RuleActivationListenerFactory.createActivationListener(RuleActivationListenerFactory.java:21)
    at org.drools.reteoo.builder.ReteooRuleBuilder.addSubRule(ReteooRuleBuilder.java:157)
    at org.drools.reteoo.builder.ReteooRuleBuilder.addRule(ReteooRuleBuilder.java:123)
    at org.drools.reteoo.ReteooBuilder.addRule(ReteooBuilder.java:110)
    at org.drools.reteoo.ReteooRuleBase.addRule(ReteooRuleBase.java:441)
    at org.drools.common.AbstractRuleBase.addRule(AbstractRuleBase.java:821)
    at org.drools.common.AbstractRuleBase.addPackages(AbstractRuleBase.java:555)
    at org.drools.reteoo.ReteooRuleBase.addPackages(ReteooRuleBase.java:458)
    at org.drools.impl.KnowledgeBaseImpl.addKnowledgePackages(KnowledgeBaseImpl.java:150)
    at it.ipiu.pch.sel.RuleTest.before(RuleTest.java:1272)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:27)
    at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:76)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:49)
    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)

Answer 1

这看起来像是一个错误，我建议您向该项目提交 JIRA。您使用的是哪个版本？

同时，您的规则比应有的更复杂。每当你在结果中看到“如果”时，这就是一个危险信号，有些事情不好。您可以将规则重写为：

rule "contact activated vs contact released"
when
    $contact : Event( type in ( EventType.CONTACT_ACTIVATED, EventType.CONTACT_RELEASED ) )
then
    retract($contact);
end