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java.lang.IllegalArgumentException: attempt to create merge event with null entity
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created by <a href="http://community.jboss.org/people/houxiaojun">Xiaojun Hou</a> in <i>jBPM</i> - <a href="http://community.jboss.org/message/614347#614347">View the full discussion</a>
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<div class="jive-rendered-content"><p><span style="color: #0000ff;">In my project,i use the code below to configure the persistence:</span></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>try {</p><p>            PoolingDataSource ds = new PoolingDataSource();</p><p>            ds.setUniqueName("jdbc/testDS");</p><p>            ds.setClassName("com.mysql.jdbc.jdbc2.optional.MysqlXADataSource");</p><p>            ds.setMaxPoolSize(3);</p><p>            ds.setAllowLocalTransactions(true);</p><p>            ds.getDriverProperties().put("user", "root");</p><p>            ds.getDriverProperties().put("password", "root");</p><p>            ds.getDriverProperties().put("URL", "jdbc:mysql://localhost:3306/jbpm5");</p><p>            ds.init();</p><p>            // load up the knowledge base</p><p>            KnowledgeBase kbase = readKnowledgeBase();</p><p>            // start a new process instance</p><p>            EntityManagerFactory emf = Persistence</p><p>                    .createEntityManagerFactory("org.jbpm.persistence.jpa");</p><p>            Environment env = KnowledgeBaseFactory.newEnvironment();</p><p>            env.set(EnvironmentName.ENTITY_MANAGER_FACTORY,</p><p>                    emf);</p><p>            env.set(EnvironmentName.TRANSACTION_MANAGER,</p><p>                    TransactionManagerServices.getTransactionManager());</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>            // create a new knowledge session that uses JPA to store the runtime</p><p>            // state</p><p>            StatefulKnowledgeSession ksession=null;</p><p>            ksession= JPAKnowledgeService.newStatefulKnowledgeSession(</p><p>                    kbase,</p><p>                    null,</p><p>                    env);</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>            JPAWorkingMemoryDbLogger logger = new JPAWorkingMemoryDbLogger(ksession);</p><p>            ksession.getWorkItemManager().registerWorkItemHandler("Human Task", new WSHumanTaskHandler());</p><p>            // start a new process instance</p><p>            Map<String, Object> params = new HashMap<String, Object>();</p><p>            params.put("employee", "krisv");</p><p>            ksession.startProcess("com.sample.evaluation",params);</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>            logger.dispose();</p><p>} catch (Throwable t) {</p><p>            t.printStackTrace();</p><p>        }</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p><span style="color: #0000ff;">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:</span></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>Registered human task listener</p><p>[2011:06:167 10:06:520:debug] Message receieved on client : AddTaskResponse</p><p>[2011:06:167 10:06:520:debug] Arguments : [1]</p><p>[2011:06:167 10:06:324:debug] Message receieved on client : EventTriggerResponse</p><p>[2011:06:167 10:06:324:debug] Arguments : [org.jbpm.task.event.EventPayload@b98a06]</p><p>Task completed 1</p><p>[2011:06:167 10:06:609:debug] Message receieved on client : GetTaskResponse</p><p>[2011:06:167 10:06:609:debug] Arguments : [org.jbpm.task.Task@2a7159ce]</p><p>[2011:06:167 10:06:610:exception] Uncaught exception on client</p><p>java.lang.IllegalArgumentException: <span style="color: #ff0000;">attempt to create merge event with null entity</span></p><p>    at org.hibernate.event.MergeEvent.<init>(MergeEvent.java:60)</p><p>    at org.hibernate.event.MergeEvent.<init>(MergeEvent.java:43)</p><p>    at org.hibernate.impl.SessionImpl.merge(SessionImpl.java:688)</p><p>    at org.hibernate.impl.SessionImpl.merge(SessionImpl.java:692)</p><p>    at org.hibernate.ejb.AbstractEntityManagerImpl.merge(AbstractEntityManagerImpl.java:235)</p><p>    at org.drools.persistence.jpa.JpaPersistenceContext.merge(JpaPersistenceContext.java:49)</p><p>    at org.drools.persistence.jpa.processinstance.JPAWorkItemManager.abortWorkItem(JPAWorkItemManager.java:136)</p><p>    at org.jbpm.process.workitem.wsht.WSHumanTaskHandler$GetCompletedTaskResponseHandler.execute(WSHumanTaskHandler.java:249)</p><p>    at org.jbpm.task.service.TaskClientHandler.messageReceived(TaskClientHandler.java:81)</p><p>    at org.jbpm.task.service.mina.MinaTaskClientHandler.messageReceived(MinaTaskClientHandler.java:47)</p><p>    at org.apache.mina.core.filterchain.DefaultIoFilterChain$TailFilter.messageReceived(DefaultIoFilterChain.java:713)</p><p>    at org.apache.mina.core.filterchain.DefaultIoFilterChain.callNextMessageReceived(DefaultIoFilterChain.java:434)</p><p>    at org.apache.mina.core.filterchain.DefaultIoFilterChain.access$1200(DefaultIoFilterChain.java:46)</p><p>    at org.apache.mina.core.filterchain.DefaultIoFilterChain$EntryImpl$1.messageReceived(DefaultIoFilterChain.java:793)</p><p>    at org.apache.mina.filter.codec.ProtocolCodecFilter$ProtocolDecoderOutputImpl.flush(ProtocolCodecFilter.java:375)</p><p>    at org.apache.mina.filter.codec.ProtocolCodecFilter.messageReceived(ProtocolCodecFilter.java:229)</p><p>    at org.apache.mina.core.filterchain.DefaultIoFilterChain.callNextMessageReceived(DefaultIoFilterChain.java:434)</p><p>    at org.apache.mina.core.filterchain.DefaultIoFilterChain.access$1200(DefaultIoFilterChain.java:46)</p><p>    at org.apache.mina.core.filterchain.DefaultIoFilterChain$EntryImpl$1.messageReceived(DefaultIoFilterChain.java:793)</p><p>    at org.apache.mina.core.filterchain.IoFilterAdapter.messageReceived(IoFilterAdapter.java:119)</p><p>    at org.apache.mina.core.filterchain.DefaultIoFilterChain.callNextMessageReceived(DefaultIoFilterChain.java:434)</p><p>    at org.apache.mina.core.filterchain.DefaultIoFilterChain.fireMessageReceived(DefaultIoFilterChain.java:426)</p><p>    at org.apache.mina.core.polling.AbstractPollingIoProcessor.read(AbstractPollingIoProcessor.java:638)</p><p>    at org.apache.mina.core.polling.AbstractPollingIoProcessor.process(AbstractPollingIoProcessor.java:598)</p><p>    at org.apache.mina.core.polling.AbstractPollingIoProcessor.process(AbstractPollingIoProcessor.java:587)</p><p>    at org.apache.mina.core.polling.AbstractPollingIoProcessor.access$400(AbstractPollingIoProcessor.java:61)</p><p>    at org.apache.mina.core.polling.AbstractPollingIoProcessor$Processor.run(AbstractPollingIoProcessor.java:969)</p><p>    at org.apache.mina.util.NamePreservingRunnable.run(NamePreservingRunnable.java:64)</p><p>    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)</p><p>    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)</p><p>    at java.lang.Thread.run(Thread.java:619)</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p><span style="color: #0000ff;">After the exception,the task stored in the database has a "completed" status</span>,Can somebody help me to solve the problem?</p></div>
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