Hello, I'm having a strange issue. I have a medium size rule file with rules like these: when InvestigationTarget( $code : identifierCode ) $s: SubjectData( identifierCode == $code ) $r: Registry( ) $y: YearData( ) from $r.years $p: Purchase( customerIdentifierCode == $s.identifierCode ) from $y.purchases then ... My application is actually still a prototype and i work building a session with facts already inserted and when the system started the user changes DRL to use with facts. My issue is when i add resource to knowledge builder. I catch an exception when exists one fact can activate the above rule: java.lang.RuntimeException: unable to invoke method: org.titan.registry.BusinessEntityData.getIdentifierCode: target of method is null at com.liferay.portal.kernel.portlet.LiferayPortlet.callActionMethod(LiferayPortlet.java:171) at com.liferay.util.bridges.mvc.MVCPortlet.callActionMethod(MVCPortlet.java:250) at com.liferay.portal.kernel.portlet.LiferayPortlet.processAction(LiferayPortlet.java:80) at com.liferay.util.bridges.mvc.MVCPortlet.processAction(MVCPortlet.java:220) at com.liferay.portlet.FilterChainImpl.doFilter(FilterChainImpl.java:70) at com.liferay.portal.kernel.portlet.PortletFilterUtil.doFilter(PortletFilterUtil.java:48) at com.liferay.portal.kernel.servlet.PortletServlet.service(PortletServlet.java:111) at javax.servlet.http.HttpServlet.service(HttpServlet.java:722) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:72) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilter.doFilter(InvokerFilter.java:73) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:684) at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:593) at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:530) at com.liferay.portlet.InvokerPortletImpl.invoke(InvokerPortletImpl.java:534) at com.liferay.portlet.InvokerPortletImpl.invokeAction(InvokerPortletImpl.java:579) at com.liferay.portlet.InvokerPortletImpl.processAction(InvokerPortletImpl.java:294) at com.liferay.portal.action.LayoutAction.processPortletRequest(LayoutAction.java:944) at com.liferay.portal.action.LayoutAction.processLayout(LayoutAction.java:688) at com.liferay.portal.action.LayoutAction.execute(LayoutAction.java:249) at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431) at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236) at com.liferay.portal.struts.PortalRequestProcessor.process(PortalRequestProcessor.java:176) at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196) at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432) at javax.servlet.http.HttpServlet.service(HttpServlet.java:641) at com.liferay.portal.servlet.MainServlet.callParentService(MainServlet.java:560) at com.liferay.portal.servlet.MainServlet.service(MainServlet.java:537) at javax.servlet.http.HttpServlet.service(HttpServlet.java:722) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:72) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116) at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:163) at com.liferay.portal.servlet.filters.secure.SecureFilter.processFilter(SecureFilter.java:294) at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:57) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:206) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:108) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilter.doFilter(InvokerFilter.java:73) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:684) at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:471) at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:402) at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:329) at com.liferay.portal.servlet.FriendlyURLServlet.service(FriendlyURLServlet.java:138) at javax.servlet.http.HttpServlet.service(HttpServlet.java:722) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:72) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116) at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:163) at com.liferay.portal.servlet.filters.strip.StripFilter.processFilter(StripFilter.java:335) at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:57) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:206) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:108) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116) at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:163) at com.liferay.portal.servlet.filters.gzip.GZipFilter.processFilter(GZipFilter.java:123) at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:57) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:206) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:108) at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:163) at com.liferay.portal.servlet.filters.secure.SecureFilter.processFilter(SecureFilter.java:294) at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:57) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:206) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:108) at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:163) at com.liferay.portal.servlet.filters.i18n.I18nFilter.processFilter(I18nFilter.java:241) at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:57) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:206) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:108) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116) at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:163) at com.liferay.portal.servlet.filters.autologin.AutoLoginFilter.processFilter(AutoLoginFilter.java:246) at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:57) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:206) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:108) at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:163) at com.liferay.portal.servlet.filters.sso.ntlm.NtlmPostFilter.processFilter(NtlmPostFilter.java:83) at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:57) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:206) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:108) at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:163) at com.liferay.portal.sharepoint.SharepointFilter.processFilter(SharepointFilter.java:80) at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:57) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:206) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:108) at com.liferay.portal.kernel.servlet.BaseFilter.processFilter(BaseFilter.java:163) at com.liferay.portal.servlet.filters.virtualhost.VirtualHostFilter.processFilter(VirtualHostFilter.java:216) at com.liferay.portal.kernel.servlet.BaseFilter.doFilter(BaseFilter.java:57) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:206) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:108) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDirectCallFilter(InvokerFilterChain.java:187) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:95) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116) at org.tuckey.web.filters.urlrewrite.UrlRewriteFilter.doFilter(UrlRewriteFilter.java:738) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDoFilter(InvokerFilterChain.java:206) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:108) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDirectCallFilter(InvokerFilterChain.java:167) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:95) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDirectCallFilter(InvokerFilterChain.java:167) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:95) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:116) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.processDirectCallFilter(InvokerFilterChain.java:187) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilterChain.doFilter(InvokerFilterChain.java:95) at com.liferay.portal.kernel.servlet.filters.invoker.InvokerFilter.doFilter(InvokerFilter.java:73) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:999) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:565) at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:309) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:619) Caused by: java.lang.RuntimeException: unable to invoke method: org.titan.registry.BusinessEntityData.getIdentifierCode: target of method is null at org.mvel2.optimizers.impl.refl.nodes.GetterAccessor.getValue(GetterAccessor.java:66) at org.mvel2.optimizers.impl.refl.nodes.VariableAccessor.getValue(VariableAccessor.java:37) at org.mvel2.ast.ASTNode.getReducedValueAccelerated(ASTNode.java:108) at org.mvel2.ast.BinaryOperation.getReducedValueAccelerated(BinaryOperation.java:107) at org.mvel2.MVELRuntime.execute(MVELRuntime.java:85) at org.mvel2.compiler.CompiledExpression.getValue(CompiledExpression.java:123) at org.mvel2.MVEL.executeExpression(MVEL.java:930) at org.drools.rule.constraint.MvelConditionEvaluator.evaluate(MvelConditionEvaluator.java:70) at org.drools.rule.constraint.MvelConditionEvaluator.evaluate(MvelConditionEvaluator.java:49) at org.drools.rule.constraint.MvelConstraint.evaluate(MvelConstraint.java:167) at org.drools.rule.constraint.MvelConstraint.isAllowedCachedLeft(MvelConstraint.java:136) at org.drools.common.SingleBetaConstraints.isAllowedCachedLeft(SingleBetaConstraints.java:130) at org.drools.reteoo.FromNode.updateSink(FromNode.java:473) at org.drools.reteoo.RuleTerminalNode.attach(RuleTerminalNode.java:344) at org.drools.reteoo.builder.ReteooRuleBuilder.addSubRule(ReteooRuleBuilder.java:168) at org.drools.reteoo.builder.ReteooRuleBuilder.addRule(ReteooRuleBuilder.java:128) at org.drools.reteoo.ReteooBuilder.addRule(ReteooBuilder.java:116) at org.drools.reteoo.ReteooRuleBase.addRule(ReteooRuleBase.java:445) at org.drools.common.AbstractRuleBase.addRule(AbstractRuleBase.java:956) at org.drools.common.AbstractRuleBase.addPackages(AbstractRuleBase.java:627) at org.drools.reteoo.ReteooRuleBase.addPackages(ReteooRuleBase.java:472) at org.drools.impl.KnowledgeBaseImpl.addKnowledgePackages(KnowledgeBaseImpl.java:150) at org.myproject.frontend.investigation.drools.DroolsInvestigationEngine.setResources(DroolsInvestigationEngine.java:137) at org.myproject.frontend.investigation.drools.filter.InvestigationFilter.setupEnvironment(InvestigationFilter.java:118) at org.myproject.frontend.investigation.drools.DroolsFilter.execute(DroolsFilter.java:19) at org.myproject.frontend.investigation.drools.DroolsInvestigationSession.executeFilter(DroolsInvestigationSession.java:64) at org.myproject.portlet.SearchResult.openGraph(SearchResult.java:86) 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 com.liferay.portal.kernel.portlet.LiferayPortlet.callActionMethod(LiferayPortlet.java:153) ... 136 more Caused by: java.lang.NullPointerException 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.mvel2.optimizers.impl.refl.nodes.GetterAccessor.getValue(GetterAccessor.java:43) ... 167 more I tried a workaround modifying rule in this way: $p: Purchase( customerIdentifierCode == $code ) from $y.purchases thus i don't catch the exception anymore, but simply the rule don't activate though it should. If anyone could help me... Best regards -- View this message in context: http://drools.46999.n3.nabble.com/Issue-in-Drools-5-5-concerned-with-rule... Sent from the Drools: User forum mailing list archive at Nabble.com.