i think that i have the same issue then in here which seems to be a bug in jbpm 5.4.
i had the same exception when trying to complete a workitem after a session reload,
By the way, i coudn't get a processInstance using :processInstance = ksession.getProcessInstance(processInstance.getId()); from the reloaded Session, i also wish to know why.
even the ksession.getProcessInstances() is empty !)
i have to mention that the task status is "completed" in the database even when this exception happens but the process do not continue to the next task.
this is the log for it the exception:
(SingleSessionCommandService.java:400) ERROR org.drools.persistence.SingleSessionCommandService - Could not commit session
java.lang.NullPointerException
at org.jbpm.process.instance.impl.ProcessInstanceImpl.setProcess(ProcessInstanceImpl.java:62)
at org.jbpm.marshalling.impl.AbstractProtobufProcessInstanceMarshaller.readProcessInstance(AbstractProtobufProcessInstanceMarshaller.java:375)
at org.jbpm.persistence.processinstance.ProcessInstanceInfo.getProcessInstance(ProcessInstanceInfo.java:142)
at org.jbpm.persistence.processinstance.JPAProcessInstanceManager.getProcessInstance(JPAProcessInstanceManager.java:91)
at org.jbpm.process.instance.ProcessRuntimeImpl.getProcessInstance(ProcessRuntimeImpl.java:206)
at org.drools.common.AbstractWorkingMemory.getProcessInstance(AbstractWorkingMemory.java:1116)
at org.drools.impl.StatefulKnowledgeSessionImpl.getProcessInstance(StatefulKnowledgeSessionImpl.java:297)
at org.drools.persistence.jpa.processinstance.JPAWorkItemManager.completeWorkItem(JPAWorkItemManager.java:117)
at org.drools.command.runtime.process.CompleteWorkItemCommand.execute(CompleteWorkItemCommand.java:69)
at org.drools.command.runtime.process.CompleteWorkItemCommand.execute(CompleteWorkItemCommand.java:32)
at org.drools.command.impl.DefaultCommandService.execute(DefaultCommandService.java:36)
at org.drools.persistence.SingleSessionCommandService.execute(SingleSessionCommandService.java:373)
at org.drools.command.impl.CommandBasedStatefulKnowledgeSession$1.completeWorkItem(CommandBasedStatefulKnowledgeSession.java:150)
at ManagedBeans.JbpmAPIUtil.StartAndCompleteTask(JbpmAPIUtil.java:372)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.apache.el.parser.AstValue.invoke(AstValue.java:264)
at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:278)
at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
at com.sun.faces.facelets.tag.jsf.core.AjaxBehaviorListenerImpl.processAjaxBehavior(AjaxHandler.java:450)
at javax.faces.event.AjaxBehaviorEvent.processListener(AjaxBehaviorEvent.java:113)
at javax.faces.component.behavior.BehaviorBase.broadcast(BehaviorBase.java:106)
at javax.faces.component.UIComponentBase.broadcast(UIComponentBase.java:760)
at javax.faces.component.UICommand.broadcast(UICommand.java:300)
at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:794)
at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1259)
at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
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:123)
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:1001)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:585)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:1770)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Thanks for help !!!