Hi, I have used 5.1 drools-api and drools-core JARs and wrote following code : String currentWorkingDirectory = System.getProperty("ofbiz.home"); kagent = KnowledgeAgentFactory.newKnowledgeAgent( "MyRuleAgent" ); String url = "file:"+currentWorkingDirectory+"/framework/drools/config/changeset.xml"; System.out.println("Url is "+url+"\t CwD "+currentWorkingDirectory); kagent.applyChangeSet( ResourceFactory.newUrlResource( url ) ); KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder(); kbuilder.add( ResourceFactory.newUrlResource( url ), ResourceType.CHANGE_SET ); kbase = kagent.getKnowledgeBase(); ResourceFactory.getResourceChangeNotifierService().start(); ResourceFactory.getResourceChangeScannerService().start(); While execution , I got following error : Service invocation error Exception: org.ofbiz.service.GenericServiceException Message: Service [ruleServiceJava] target threw an unexpected exception (org/drools/rule/CompositeClassLoader) ---- cause --------------------------------------------------------------------- Exception: java.lang.NoClassDefFoundError Message: org/drools/rule/CompositeClassLoader ---- stack trace --------------------------------------------------------------- java.lang.NoClassDefFoundError: org/drools/rule/CompositeClassLoader org.drools.builder.impl.KnowledgeBuilderFactoryServiceImpl.newKnowledgeBuilder(KnowledgeBuilderFactoryServiceImpl.java:34) org.drools.builder.KnowledgeBuilderFactory.newKnowledgeBuilder(KnowledgeBuilderFactory.java:47) org.drools.agent.impl.KnowledgeAgentImpl.createKBuilder(KnowledgeAgentImpl.java:1214) org.drools.agent.impl.KnowledgeAgentImpl.addResourcesToKnowledgeBase(KnowledgeAgentImpl.java:884) org.drools.agent.impl.KnowledgeAgentImpl.rebuildResources(KnowledgeAgentImpl.java:704) org.drools.agent.impl.KnowledgeAgentImpl.buildKnowledgeBase(KnowledgeAgentImpl.java:584) org.drools.agent.impl.KnowledgeAgentImpl.applyChangeSet(KnowledgeAgentImpl.java:185) org.drools.agent.impl.KnowledgeAgentImpl.applyChangeSet(KnowledgeAgentImpl.java:168) org.ofbiz.drools.event.drool.RuleIntegrate.createKnowledgeBase(RuleIntegrate.java:46) org.ofbiz.drools.event.drool.RuleIntegrate.createWorkingMemory(RuleIntegrate.java:29) org.ofbiz.payroll.DroolsRule.callRuleJava(DroolsRule.java:42) sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) java.lang.reflect.Method.invoke(Method.java:597) org.ofbiz.service.engine.StandardJavaEngine.serviceInvoker(StandardJavaEngine.java:100) org.ofbiz.service.engine.StandardJavaEngine.runSync(StandardJavaEngine.java:57) org.ofbiz.service.ModelServiceReader$GenericInvokerImpl.runSync(ModelServiceReader.java:761) _$gen.file_58$.D_58$.Swapnil_95$Data.ofbiz_95$payroll.ofbiz_45$17_45$Aug_45$2010.applications.payroll.servicedef.services _46$xml_35$ruleServiceJava.runSync(file:/D:/Swapnil_Data/ofbiz_payroll/ofbiz-17-Aug-2010/applications/payroll/servicedef/ services.xml#ruleServiceJava:114) org.ofbiz.service.ServiceDispatcher.runSync(ServiceDispatcher.java:399) org.ofbiz.service.ServiceDispatcher.runSync(ServiceDispatcher.java:226) org.ofbiz.service.GenericDispatcher.runSync(GenericDispatcher.java:165) org.ofbiz.webapp.event.ServiceEventHandler.invoke(ServiceEventHandler.java:336) org.ofbiz.webapp.control.RequestHandler.runEvent(RequestHandler.java:637) org.ofbiz.webapp.control.RequestHandler.doRequest(RequestHandler.java:383) org.ofbiz.webapp.control.ControlServlet.doGet(ControlServlet.java:227) org.ofbiz.webapp.control.ControlServlet.doPost(ControlServlet.java:90) javax.servlet.http.HttpServlet.service(HttpServlet.java:637) javax.servlet.http.HttpServlet.service(HttpServlet.java:717) org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) org.ofbiz.webapp.control.ContextFilter.doFilter(ContextFilter.java:271) org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:555) org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852) org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) java.lang.Thread.run(Thread.java:619) -------------------------------------------------------------------------------- Then I check drools-core.jar in version 5 and in 5.1 too. The problem I found was 'org/drools/rule/CompositeClassLoader' class was present in 5.0 version but was not there in 5.1 . Pl help me in resolving this issue. Thanks, Swapnil Sawant -- View this message in context: http://drools-java-rules-engine.46999.n3.nabble.com/Error-while-applying-... Sent from the Drools - User mailing list archive at Nabble.com.