Maven Project Java 1.8中的Drools 6.4.0.final问题

Question

Gettind this error while creating bean.

Caused by: java.lang.IllegalArgumentException: Unable to instantiate service for Class 'org.drools.builder.KnowledgeBuilderFactoryService'
at org.drools.util.ServiceRegistryImpl.get(ServiceRegistryImpl.java:162)
at org.drools.builder.KnowledgeBuilderFactory.loadServiceFactory(KnowledgeBuilderFactory.java:130)
at org.drools.builder.KnowledgeBuilderFactory.getKnowledgeBuilderServiceFactory(KnowledgeBuilderFactory.java:124)
at org.drools.builder.KnowledgeBuilderFactory.newKnowledgeBuilder(KnowledgeBuilderFactory.java:46)
at com.snapdeal.qualityscore.engine.cache.impl.DroolsRuleBaseCache.getDroolsRuleBase(DroolsRuleBaseCache.java:80)
at com.snapdeal.qualityscore.engine.cache.impl.DroolsRuleBaseCache.populateRuleBase(DroolsRuleBaseCache.java:52)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleElement.invoke(InitDestroyAnnotationBeanPostProcessor.java:349)
at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleMetadata.invokeInitMethods(InitDestroyAnnotationBeanPostProcessor.java:300)
at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor.postProcessBeforeInitialization(InitDestroyAnnotationBeanPostProcessor.java:133)
... 27 more
Caused by: java.lang.IllegalArgumentException: Unable to instantiate 'org.drools.builder.impl.KnowledgeBuilderFactoryServiceImpl'
at org.drools.util.ServiceRegistryImpl$ReflectionInstantiator.newInstance(ServiceRegistryImpl.java:213)
at org.drools.util.ServiceRegistryImpl$ReflectionInstantiator.call(ServiceRegistryImpl.java:205)
at org.drools.util.ServiceRegistryImpl.get(ServiceRegistryImpl.java:160)
... 39 more
Caused by: java.lang.ClassNotFoundException: org.drools.builder.impl.KnowledgeBuilderFactoryServiceImpl
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1714)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1559)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:264)
at org.drools.util.ServiceRegistryImpl$ReflectionInstantiator.newInstance(ServiceRegistryImpl.java:210)
... 41 more

Which clearly says that KnowledgeBuilderFactoryServiceImpl is not found. But I don't understand why is not that class found its internal drools issue I guess..

Anyways here is my code if anybody can help?

public static KnowledgeBase getDroolsRuleBase(List<InputStream> drlStreams) throws Exception{
    KnowledgeBuilder packageBuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();
    KnowledgeBase ruleBase = KnowledgeBaseFactory.newKnowledgeBase();
    for (InputStream inputStream : drlStreams)
    {
        try{
            packageBuilder.add(ResourceFactory.newInputStreamResource(inputStream), ResourceType.DRL);
            ruleBase.addKnowledgePackages(packageBuilder.getKnowledgePackages());
        }
        catch(Exception e){
            throw new Exception("Rule Base Package Build Failed");
        }
    }
    return ruleBase;
}

Answer 1

Make sure you have drools-compiler dependency in your project:

  <dependency>
      <groupId>org.drools</groupId>
      <artifactId>drools-compiler</artifactId>
      <version>6.4.0.Final</version>
  </dependency>

Drools sometimes uses reflection to instantiate its internal classes. These could explain your ClassNotFoundException .

Hope it helps,