Bing Lim [https://community.jboss.org/people/binglim] created the discussion "Error message while using JPAKnowledgeService and how to do external Signaling with persistence" To view the discussion, visit: https://community.jboss.org/message/751986#751986 -------------------------------------------------------------- Hi, I am trying to use persistence such that an external signaling can continue a workflow process that is in a wait-state. (I plan on running SignalEvent.java after ProcessMain is in a wait state to trigger the signal node and continue with the workflow) https://community.jboss.org/servlet/JiveServlet/showImage/2-751986-19148/... https://community.jboss.org/servlet/JiveServlet/downloadImage/2-751986-19... However, I get these errors when I run ProcessMain.java. Exception in thread "main" java.lang.IllegalStateException: java.lang.reflect.InvocationTargetException           at org.drools.persistence.jpa.KnowledgeStoreServiceImpl.buildCommandService(KnowledgeStoreServiceImpl.java:143)           at org.drools.persistence.jpa.KnowledgeStoreServiceImpl.newStatefulKnowledgeSession(KnowledgeStoreServiceImpl.java:67)           at org.drools.persistence.jpa.JPAKnowledgeService.newStatefulKnowledgeSession(JPAKnowledgeService.java:122)           at com.sample.ProcessMain.main(ProcessMain.java:62) Caused by: java.lang.reflect.InvocationTargetException           at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)           at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)           at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)           at java.lang.reflect.Constructor.newInstance(Unknown Source)           at org.drools.persistence.jpa.KnowledgeStoreServiceImpl.buildCommandService(KnowledgeStoreServiceImpl.java:129)           ... 3 more Caused by: java.lang.NullPointerException           at org.drools.persistence.SingleSessionCommandService.<init>(SingleSessionCommandService.java:168)           ... 8 more 1) I read the documentations and it states: // recreate the session from database using the sessionId ksession = JPAKnowledgeService.loadStatefulKnowledgeSession( sessionId, kbase, null, env ); Does the kbase has to be the original knowledgebase? or am I allowed to create a new knowledgebase but as long as the sessionId is correct, I can signal a bpmn workflow externally that is on a different knowledgebase? 2) Can someone elaborate what the error message means and how to do external signaling with persistence and JPAKnowledgeService? Any help is appreciated. Thanks! Best, Bing -------------------------------------------------------------- Reply to this message by going to Community [https://community.jboss.org/message/751986#751986] Start a new discussion in jBPM at Community [https://community.jboss.org/choose-container!input.jspa?contentType=1&...]