Xiaojun Hou [http://community.jboss.org/people/houxiaojun] created the discussion "java.lang.IllegalArgumentException: attempt to create merge event with null entity" To view the discussion, visit: http://community.jboss.org/message/614347#614347 -------------------------------------------------------------- In my project,i use the code below to configure the persistence: try {             PoolingDataSource ds = new PoolingDataSource();             ds.setUniqueName("jdbc/testDS");             ds.setClassName("com.mysql.jdbc.jdbc2.optional.MysqlXADataSource");             ds.setMaxPoolSize(3);             ds.setAllowLocalTransactions(true);             ds.getDriverProperties().put("user", "root");             ds.getDriverProperties().put("password", "root");             ds.getDriverProperties().put("URL", "jdbc:mysql://localhost:3306/jbpm5");             ds.init();             // load up the knowledge base             KnowledgeBase kbase = readKnowledgeBase();             // start a new process instance             EntityManagerFactory emf = Persistence                     .createEntityManagerFactory("org.jbpm.persistence.jpa");             Environment env = KnowledgeBaseFactory.newEnvironment();             env.set(EnvironmentName.ENTITY_MANAGER_FACTORY,                     emf);             env.set(EnvironmentName.TRANSACTION_MANAGER,                     TransactionManagerServices.getTransactionManager());             // create a new knowledge session that uses JPA to store the runtime             // state             StatefulKnowledgeSession ksession=null;             ksession= JPAKnowledgeService.newStatefulKnowledgeSession(                     kbase,                     null,                     env);             JPAWorkingMemoryDbLogger logger = new JPAWorkingMemoryDbLogger(ksession);             ksession.getWorkItemManager().registerWorkItemHandler("Human Task", new WSHumanTaskHandler());             // start a new process instance             Map<String, Object> params = new HashMap<String, Object>();             params.put("employee", "krisv");             ksession.startProcess("com.sample.evaluation",params);             logger.dispose(); } catch (Throwable t) {             t.printStackTrace();         } However,when i start a new processinstance(I have three task in my process) and try to complete the first task,exception happens just like this: Registered human task listener [2011:06:167 10:06:520:debug] Message receieved on client : AddTaskResponse [2011:06:167 10:06:520:debug] Arguments : [1] [2011:06:167 10:06:324:debug] Message receieved on client : EventTriggerResponse [2011:06:167 10:06:324:debug] Arguments : [org.jbpm.task.event.EventPayload@b98a06] Task completed 1 [2011:06:167 10:06:609:debug] Message receieved on client : GetTaskResponse [2011:06:167 10:06:609:debug] Arguments : [org.jbpm.task.Task@2a7159ce] [2011:06:167 10:06:610:exception] Uncaught exception on client java.lang.IllegalArgumentException: attempt to create merge event with null entity     at org.hibernate.event.MergeEvent.<init>(MergeEvent.java:60)     at org.hibernate.event.MergeEvent.<init>(MergeEvent.java:43)     at org.hibernate.impl.SessionImpl.merge(SessionImpl.java:688)     at org.hibernate.impl.SessionImpl.merge(SessionImpl.java:692)     at org.hibernate.ejb.AbstractEntityManagerImpl.merge(AbstractEntityManagerImpl.java:235)     at org.drools.persistence.jpa.JpaPersistenceContext.merge(JpaPersistenceContext.java:49)     at org.drools.persistence.jpa.processinstance.JPAWorkItemManager.abortWorkItem(JPAWorkItemManager.java:136)     at org.jbpm.process.workitem.wsht.WSHumanTaskHandler$GetCompletedTaskResponseHandler.execute(WSHumanTaskHandler.java:249)     at org.jbpm.task.service.TaskClientHandler.messageReceived(TaskClientHandler.java:81)     at org.jbpm.task.service.mina.MinaTaskClientHandler.messageReceived(MinaTaskClientHandler.java:47)     at org.apache.mina.core.filterchain.DefaultIoFilterChain$TailFilter.messageReceived(DefaultIoFilterChain.java:713)     at org.apache.mina.core.filterchain.DefaultIoFilterChain.callNextMessageReceived(DefaultIoFilterChain.java:434)     at org.apache.mina.core.filterchain.DefaultIoFilterChain.access$1200(DefaultIoFilterChain.java:46)     at org.apache.mina.core.filterchain.DefaultIoFilterChain$EntryImpl$1.messageReceived(DefaultIoFilterChain.java:793)     at org.apache.mina.filter.codec.ProtocolCodecFilter$ProtocolDecoderOutputImpl.flush(ProtocolCodecFilter.java:375)     at org.apache.mina.filter.codec.ProtocolCodecFilter.messageReceived(ProtocolCodecFilter.java:229)     at org.apache.mina.core.filterchain.DefaultIoFilterChain.callNextMessageReceived(DefaultIoFilterChain.java:434)     at org.apache.mina.core.filterchain.DefaultIoFilterChain.access$1200(DefaultIoFilterChain.java:46)     at org.apache.mina.core.filterchain.DefaultIoFilterChain$EntryImpl$1.messageReceived(DefaultIoFilterChain.java:793)     at org.apache.mina.core.filterchain.IoFilterAdapter.messageReceived(IoFilterAdapter.java:119)     at org.apache.mina.core.filterchain.DefaultIoFilterChain.callNextMessageReceived(DefaultIoFilterChain.java:434)     at org.apache.mina.core.filterchain.DefaultIoFilterChain.fireMessageReceived(DefaultIoFilterChain.java:426)     at org.apache.mina.core.polling.AbstractPollingIoProcessor.read(AbstractPollingIoProcessor.java:638)     at org.apache.mina.core.polling.AbstractPollingIoProcessor.process(AbstractPollingIoProcessor.java:598)     at org.apache.mina.core.polling.AbstractPollingIoProcessor.process(AbstractPollingIoProcessor.java:587)     at org.apache.mina.core.polling.AbstractPollingIoProcessor.access$400(AbstractPollingIoProcessor.java:61)     at org.apache.mina.core.polling.AbstractPollingIoProcessor$Processor.run(AbstractPollingIoProcessor.java:969)     at org.apache.mina.util.NamePreservingRunnable.run(NamePreservingRunnable.java:64)     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) After the exception,the task stored in the database has a "completed" status,Can somebody help me to solve the problem? -------------------------------------------------------------- Reply to this message by going to Community [http://community.jboss.org/message/614347#614347] Start a new discussion in jBPM at Community [http://community.jboss.org/choose-container!input.jspa?contentType=1&...]