Description:
1). Post a message on a queue in EMS broker setting JMS expiration to a value in seconds. No receivers are running on the queue.

2). Subscribe to monitor topic for that particular queue to receive monitor messages when a message prematurely exits due to expiration.

3). When the subscriber starts and tries to receive the monitor message, it fails with a parsing error and a Null pointer exception.
Symptoms:
The Topic Subscriber activity fails with the following exception:

<?xml version = "1.0" encoding = "UTF-8"?>
<ns0:ErrorReport xmlns:ns0 = "http://www.tibco.com/pe/EngineTypes">
    <StackTrace>Job-44001 Error in [BusinessProject/BusinessProcesses/MainProcesses/receiveAlertSummaryEmailMessage.process/JMS Topic Subscriber]
There was an error while parsing a message.
    at com.tibco.plugin.jms.service.JMSEventContextProcessor.postProcess(JMSEventContextProcessor.java:47)
    at com.tibco.plugin.share.jms.impl.JMSEventContext.postProcess(JMSEventContext.java:232)
    at com.tibco.pe.core.ProcessGroup.eval(ProcessGroup.java:54)
    at com.tibco.pe.plugin.Activity.eval(Activity.java:241)
    at com.tibco.pe.core.TaskImpl.eval(TaskImpl.java:574)
    at com.tibco.pe.core.Job.a(Job.java:712)
    at com.tibco.pe.core.Job.k(Job.java:501)
    at com.tibco.pe.core.JobDispatcher$JobCourier.a(JobDispatcher.java:249)
    at com.tibco.pe.core.JobDispatcher$JobCourier.run(JobDispatcher.java:200)
caused by: com.tibco.plugin.share.jms.impl.JMSExceptionWrapper: java.lang.NullPointerException
    at com.tibco.plugin.share.jms.impl.JMSPluginException.<init>(JMSPluginException.java:22)
    at com.tibco.plugin.share.jms.impl.JMSReceiveException.<init>(JMSReceiveException.java:15)
    at com.tibco.plugin.jms.service.JMSEventContextProcessor.postProcess(JMSEventContextProcessor.java:47)
    at com.tibco.plugin.share.jms.impl.JMSEventContext.postProcess(JMSEventContext.java:232)
    at com.tibco.pe.core.ProcessGroup.eval(ProcessGroup.java:54)
    at com.tibco.pe.plugin.Activity.eval(Activity.java:241)
    at com.tibco.pe.core.TaskImpl.eval(TaskImpl.java:574)
    at com.tibco.pe.core.Job.a(Job.java:712)
    at com.tibco.pe.core.Job.k(Job.java:501)
    at com.tibco.pe.core.JobDispatcher$JobCourier.a(JobDispatcher.java:249)
    at com.tibco.pe.core.JobDispatcher$JobCourier.run(JobDispatcher.java:200)
Caused by: java.lang.NullPointerException
    at com.tibco.plugin.share.jms.service.JMSMessageDeserializer.for(JMSMessageDeserializer.java:439)
    at com.tibco.plugin.share.jms.service.JMSMessageDeserializer.messageToXiNode(JMSMessageDeserializer.java:115)
    at com.tibco.plugin.jms.service.JMSEventContextProcessor.postProcess(JMSEventContextProcessor.java:40)
    ... 8 more
    </StackTrace>
    <Msg>There was an error while parsing a message.</Msg>
    <FullClass>com.tibco.plugin.share.jms.impl.JMSReceiveException</FullClass>
    <Class>JMSReceiveException</Class>
    <ProcessStack>BusinessProject/BusinessProcesses/MainProcesses/receiveAlertSummaryEmailMessage.process/JMS Topic Subscriber</ProcessStack>
    <MsgCode>BW-JMS-100043</MsgCode>
    <Data>
        <ns1:JMSReceiveException xmlns:ns1 = "http://schemas.tibco.com/bw/plugins/jms/5.0/jmsExceptions">
            <msg>There was an error while parsing a message.</msg>
            <msgCode>BW-JMS-100043</msgCode>
        </ns1:JMSReceiveException>
    </Data>
</ns0:ErrorReport>

Cause:
The type of messages published on $sys.monitor.> topics by the EMS server is a MapMessage. They are not the regular TextMessage. In your BW TopicSubscriber if you set the message type as Text Message, the message parsing will fail which will trigger a “NullPointer Exception” which is an expected behavior. You can run a standlone Java TopicSubscriber shipped with EMS installation to see how the message looks like and create an appropriate mapping in your BW Topic Subscriber according to it.

JMS Topic Subscriber activity fails with a Null Pointer exception when subscribing to a monitoring topic message.

Set the “Message Type” of the JMS Topic Subscriber activity to Map Message and after the TopicSubscriber activity, add a Java code activity for which binary input will be the Message Bytes of the TopicSubscriber activity. Processs the Message Bytes in the Java code as follows:

Message msg = Tibjms.createFromBytes(getinput());
setoutput(((TextMessage)msg).getText());

Now the output of the Java code will contain the text body of the message that expired from the queue. Attached is a sample BW project that achieves this. (Filename: MonitorExpiry.zip).