我们将 Spring Batch 2.1.9 与 Spring 3.1.1 一起使用，并设置了Job执行以下操作的 a：
- JMS
ItemReader（使用 ActiveMQ 5.6.0）读取传入消息，传递给： ItemWriter发送批量电子邮件的一个。
这全部部署为 WAR，在 Weblogic 10.3.x 下运行。ItemReader现在，我们已经让这个设计在其他地方正常工作，但是在这个特定的部署中，如果在大量不活动之后向该设备发送一条新消息，则会发生以下情况：
09:20:28,155 - DEBUG (org.springframework.batch.repeat.support.RepeatTemplate) - Repeat operation about to start at count=2
10:39:38,733 - WARN (org.springframework.jms.connection.CachingConnectionFactory) - Encountered a JMSException - resetting the underlying JMS Connection
javax.jms.JMSException: Unexpected error occured: java.lang.NoClassDefFoundError: org/apache/activemq/command/ActiveMQObjectMessage
at org.apache.activemq.util.JMSExceptionSupport.create(JMSExceptionSupport.java:49)
at org.apache.activemq.ActiveMQConnection.onAsyncException(ActiveMQConnection.java:1934)
at org.apache.activemq.ActiveMQConnection.onException(ActiveMQConnection.java:1951)
at org.apache.activemq.transport.TransportFilter.onException(TransportFilter.java:101)
at org.apache.activemq.transport.ResponseCorrelator.onException(ResponseCorrelator.java:126)
at org.apache.activemq.transport.TransportFilter.onException(TransportFilter.java:101)
at org.apache.activemq.transport.TransportFilter.onException(TransportFilter.java:101)
at org.apache.activemq.transport.WireFormatNegotiator.onException(WireFormatNegotiator.java:160)
at org.apache.activemq.transport.AbstractInactivityMonitor.onException(AbstractInactivityMonitor.java:268)
at org.apache.activemq.transport.TransportSupport.onException(TransportSupport.java:96)
at org.apache.activemq.transport.tcp.TcpTransport.run(TcpTransport.java:213)
at java.lang.Thread.run(Thread.java:662)
Caused by: java.io.IOException: Unexpected error occured: java.lang.NoClassDefFoundError: org/apache/activemq/command/ActiveMQObjectMessage
at org.apache.activemq.transport.tcp.TcpTransport.run(TcpTransport.java:211)
... 1 more
Caused by: java.lang.NoClassDefFoundError: org/apache/activemq/command/ActiveMQObjectMessage
at org.apache.activemq.openwire.v9.ActiveMQObjectMessageMarshaller.createObject(ActiveMQObjectMessageMarshaller.java:55)
at org.apache.activemq.openwire.OpenWireFormat.tightUnmarshalNestedObject(OpenWireFormat.java:446)
at org.apache.activemq.openwire.v9.BaseDataStreamMarshaller.tightUnmarsalNestedObject(BaseDataStreamMarshaller.java:125)
at org.apache.activemq.openwire.v9.MessageDispatchMarshaller.tightUnmarshal(MessageDispatchMarshaller.java:71)
at org.apache.activemq.openwire.OpenWireFormat.doUnmarshal(OpenWireFormat.java:371)
at org.apache.activemq.openwire.OpenWireFormat.unmarshal(OpenWireFormat.java:285)
at org.apache.activemq.transport.tcp.TcpTransport.readCommand(TcpTransport.java:229)
at org.apache.activemq.transport.tcp.TcpTransport.doRun(TcpTransport.java:221)
at org.apache.activemq.transport.tcp.TcpTransport.run(TcpTransport.java:204)
... 1 more
Caused by: java.lang.ClassNotFoundException: org.apache.activemq.command.ActiveMQObjectMessage
at weblogic.utils.classloaders.GenericClassLoader.findLocalClass(GenericClassLoader.java:297)
at weblogic.utils.classloaders.GenericClassLoader.findClass(GenericClassLoader.java:270)
at weblogic.utils.classloaders.ChangeAwareClassLoader.findClass(ChangeAwareClassLoader.java:64)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
at weblogic.utils.classloaders.GenericClassLoader.loadClass(GenericClassLoader.java:179)
at weblogic.utils.classloaders.ChangeAwareClassLoader.loadClass(ChangeAwareClassLoader.java:43)
... 10 more
随后似乎是一个会话关闭（我们使用的是 Spring 的CachingConnectionFactory，FWIW）
10:39:38,780 - DEBUG (org.springframework.batch.core.step.item.FaultTolerantChunkProvider) - Skipping failed input
org.springframework.jms.IllegalStateException: The Session is closed; nested exception is javax.jms.IllegalStateException: The Session is closed
at org.springframework.jms.support.JmsUtils.convertJmsAccessException(JmsUtils.java:279)
at org.springframework.jms.support.JmsAccessor.convertJmsAccessException(JmsAccessor.java:168)
at org.springframework.jms.core.JmsTemplate.execute(JmsTemplate.java:469)
at org.springframework.jms.core.JmsTemplate.receiveSelected(JmsTemplate.java:695)
at org.springframework.jms.core.JmsTemplate.receive(JmsTemplate.java:677)
at org.springframework.jms.core.JmsTemplate.receive(JmsTemplate.java:669)
at org.springframework.jms.core.JmsTemplate.receiveAndConvert(JmsTemplate.java:787)
at org.springframework.batch.item.jms.JmsItemReader.read(JmsItemReader.java:84)
at our.code.spring.batch.AquilaJmsItemReader.read(AquilaJmsItemReader.java:61)
at org.springframework.batch.core.step.item.SimpleChunkProvider.doRead(SimpleChunkProvider.java:90)
at org.springframework.batch.core.step.item.FaultTolerantChunkProvider.read(FaultTolerantChunkProvider.java:87)
at org.springframework.batch.core.step.item.SimpleChunkProvider$1.doInIteration(SimpleChunkProvider.java:110)
at org.springframework.batch.repeat.support.RepeatTemplate.getNextResult(RepeatTemplate.java:367)
at org.springframework.batch.repeat.support.RepeatTemplate.executeInternal(RepeatTemplate.java:214)
at org.springframework.batch.repeat.support.RepeatTemplate.iterate(RepeatTemplate.java:143)
at org.springframework.batch.core.step.item.SimpleChunkProvider.provide(SimpleChunkProvider.java:105)
at org.springframework.batch.core.step.item.ChunkOrientedTasklet.execute(ChunkOrientedTasklet.java:68)
at org.springframework.batch.core.step.tasklet.TaskletStep$ChunkTransactionCallback.doInTransaction(TaskletStep.java:386)
at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:130)
at org.springframework.batch.core.step.tasklet.TaskletStep$2.doInChunkContext(TaskletStep.java:264)
at org.springframework.batch.core.scope.context.StepContextRepeatCallback.doInIteration(StepContextRepeatCallback.java:76)
at org.springframework.batch.repeat.support.RepeatTemplate.getNextResult(RepeatTemplate.java:367)
at org.springframework.batch.repeat.support.RepeatTemplate.executeInternal(RepeatTemplate.java:214)
at org.springframework.batch.repeat.support.RepeatTemplate.iterate(RepeatTemplate.java:143)
at org.springframework.batch.core.step.tasklet.TaskletStep.doExecute(TaskletStep.java:250)
at org.springframework.batch.core.step.AbstractStep.execute(AbstractStep.java:195)
at org.springframework.batch.core.job.SimpleStepHandler.handleStep(SimpleStepHandler.java:135)
at org.springframework.batch.core.job.flow.JobFlowExecutor.executeStep(JobFlowExecutor.java:61)
at org.springframework.batch.core.job.flow.support.state.StepState.handle(StepState.java:60)
at org.springframework.batch.core.job.flow.support.SimpleFlow.resume(SimpleFlow.java:144)
at org.springframework.batch.core.job.flow.support.SimpleFlow.start(SimpleFlow.java:124)
at org.springframework.batch.core.job.flow.FlowJob.doExecute(FlowJob.java:135)
at org.springframework.batch.core.job.AbstractJob.execute(AbstractJob.java:293)
at org.springframework.batch.core.launch.support.SimpleJobLauncher$1.run(SimpleJobLauncher.java:120)
at java.lang.Thread.run(Thread.java:662)
Caused by: javax.jms.IllegalStateException: The Session is closed
at org.apache.activemq.ActiveMQSession.checkClosed(ActiveMQSession.java:731)
at org.apache.activemq.ActiveMQSession.getTransacted(ActiveMQSession.java:521)
at sun.reflect.GeneratedMethodAccessor320.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.jms.connection.CachingConnectionFactory$CachedSessionInvocationHandler.invoke(CachingConnectionFactory.java:348)
at $Proxy1006.getTransacted(Unknown Source)
at org.springframework.jms.core.JmsTemplate.doReceive(JmsTemplate.java:742)
at org.springframework.jms.core.JmsTemplate.doReceive(JmsTemplate.java:722)
at org.springframework.jms.core.JmsTemplate$9.doInJms(JmsTemplate.java:697)
at org.springframework.jms.core.JmsTemplate$9.doInJms(JmsTemplate.java:1)
at org.springframework.jms.core.JmsTemplate.execute(JmsTemplate.java:466)
... 32 more
在大约 20 次左右的NoClassDefFoundError跟踪之后，读取操作完成：
10:39:41,624 - DEBUG (org.springframework.batch.repeat.support.RepeatTemplate) - Repeat is complete according to policy and result value.
10:39:41,624 - DEBUG (org.springframework.batch.core.step.item.ChunkOrientedTasklet) - Inputs not busy, ended: false
10:39:41,624 - DEBUG (org.springframework.batch.core.step.tasklet.TaskletStep) - Applying contribution: [StepContribution: read=0, written=0, filtered=0, readSkips=100, writeSkips=0, processSkips=0, exitStatus=EXECUTING]
10:39:41,639 - DEBUG (org.springframework.batch.core.step.tasklet.TaskletStep) - Saving step execution before commit: StepExecution: id=1, version=5, name=fetchEmailsStep, status=STARTED, exitStatus=EXECUTING, readCount=0, filterCount=0, writeCount=0 readSkipCount=500, writeSkipCount=0, processSkipCount=0, commitCount=5, rollbackCount=0, exitDescription=
10:39:41,639 - DEBUG (org.springframework.batch.repeat.support.RepeatTemplate) - Repeat operation about to start at count=6
10:39:41,639 - DEBUG (org.springframework.batch.core.scope.context.StepContextRepeatCallback) - Preparing chunk execution for StepContext: org.springframework.batch.core.scope.context.StepContext@306897b6
10:39:41,639 - DEBUG (org.springframework.batch.core.scope.context.StepContextRepeatCallback) - Chunk execution starting: queue size=0
10:39:41,639 - DEBUG (org.springframework.batch.repeat.support.RepeatTemplate) - Starting repeat context.
10:39:41,639 - DEBUG (org.springframework.batch.repeat.support.RepeatTemplate) - Repeat operation about to start at count=1
但最终结果是我们的消息没有传递给ItemWriter
谁能解释为什么我们可能会突然NoClassDefFoundError出错？
我真的很想避免为了解决 Weblogic 类加载器问题而不得不开始改变我们的部署方式，例如必须将 ActiveMQ JAR 移动到 \server\lib 等。
我们的 Spring 配置：
<bean id="jmsEmailFetcher" class="our.code.batch.AquilaJmsItemReader">
<property name="jmsTemplate" ref="batchEmailJmsTemplate" />
</bean>
<bean id="batchEmailJmsTemplate" class="org.springframework.jms.core.JmsTemplate">
<property name="connectionFactory" ref="springBatchJmsCachingConnF"/>
<property name="defaultDestination" ref="springBatchIncomingEmailQueue" />
<!-- Do *not* need to set a timeout: <property name="receiveTimeout" value="1800000" /> -->
</bean>
<bean id="springBatchJmsCachingConnF" class="org.springframework.jms.connection.CachingConnectionFactory">
<property name="targetConnectionFactory" ref="srcConnectionFactory"/>
<property name="reconnectOnException" value="true"/>
<!-- Leave "sessionCacheSize" as default (1) until we have a better answer -->
</bean>
<jee:jndi-lookup id="srcConnectionFactory" jndi-name="${jndi.jms.connfactory}">
<jee:environment>
java.naming.factory.initial = <snip>
java.naming.provider.url = <snip>
</jee:environment>
</jee:jndi-lookup>