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| JMS: Getting Message Payload with RFH2 Header |
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| bloehle13 |
 Posted: Fri Apr 23, 2021 3:48 am Post subject: JMS: Getting Message Payload with RFH2 Header |
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Newbie
Joined: 27 Jan 2021
Posts: 6
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Our JMS MessageListener listens for MQ Application Activity Trace messages. These come through as ByteMessages, and in the bytes of the message I can see the message payload with the RFH2 headers that were set by the traced message. When I create an MQMessage from this BytesMessage though, the message data is empty. I've attached my code below. How can I get the message data with the RFH2 headers from the MQMessage object?
| Code: |
// Convert generic jms Message object to BytesMessage
BytesMessage bytesMsg = (BytesMessage) message;
// Read bytes of BytesMessage
byte[] byteData = null;
byteData = new byte[(int) bytesMsg.getBodyLength()];
bytesMsg.readBytes(byteData);
// Create MQMessage from BytesMessage data
mqMsg = new MQMessage();
mqMsg.write(byteData);
mqMsg.seek(0);
// Print MQMessage data
// MQCFGR grpHeader is instantiated earlier
byte[] b = grpHeader.getParameterValue(MQConstants.MQBACF_MESSAGE_DATA) == null ? new byte[] {} : grpHeader.getBytesParameterValue(MQConstants.MQBACF_MESSAGE_DATA);
System.out.println("Payload bytes from group header length: " + b.length);// prints 0
System.out.println("Payload from group header: " + new String(b)); // prints empty String
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| RogerLacroix |
| Posted: Fri Apr 23, 2021 3:15 pm Post subject: Re: JMS: Getting Message Payload with RFH2 Header |
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Jedi Knight
Joined: 15 May 2001
Posts: 3264
Location: London, ON Canada
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| bloehle13 wrote: |
| Code: |
// Convert generic jms Message object to BytesMessage
BytesMessage bytesMsg = (BytesMessage) message;
// Read bytes of BytesMessage
byte[] byteData = null;
byteData = new byte[(int) bytesMsg.getBodyLength()];
bytesMsg.readBytes(byteData);
// Create MQMessage from BytesMessage data
mqMsg = new MQMessage();
mqMsg.write(byteData);
mqMsg.seek(0);
// Print MQMessage data
// MQCFGR grpHeader is instantiated earlier
byte[] b = grpHeader.getParameterValue(MQConstants.MQBACF_MESSAGE_DATA) == null ? new byte[] {} : grpHeader.getBytesParameterValue(MQConstants.MQBACF_MESSAGE_DATA);
System.out.println("Payload bytes from group header length: " + b.length);// prints 0
System.out.println("Payload from group header: " + new String(b)); // prints empty String
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I see that you are setting 'mqMsg' with some data but I don't see anywhere in the code where you are accessing/reading it.
| bloehle13 wrote: |
| Code: |
| byte[] b = grpHeader.getParameterValue(MQConstants.MQBACF_MESSAGE_DATA) == null ? new byte[] {} : grpHeader.getBytesParameterValue(MQConstants.MQBACF_MESSAGE_DATA); |
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Clearly, that parameter doesn't exist in data. Also, your code would run faster if you coded as follows:
| Code: |
byte[] b = grpHeader.getBytesParameterValue(MQConstants.MQBACF_MESSAGE_DATA);
if (null == b)
b = new byte[0]; |
Avoid double 'get' calls. Each time the MQ library has to search for the parameter. Don't do it twice when once can get the job done. Also, my way is a lot easier to read rather than 1 super long line of code.
Regards,
Roger Lacroix
Capitalware Inc.
_________________
Capitalware: Transforming tomorrow into today.
Connected to MQ!
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| bloehle13 |
| Posted: Fri May 07, 2021 11:55 am Post subject: |
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Newbie
Joined: 27 Jan 2021
Posts: 6
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Thanks for the reply Roger. mqMsg was getting populated by a BytesMessage that comes from an onMessage() MessageDrivenBean.
The solution turned out to be that I had to loop through the PCFParameter parameters looking for MQBACF_MESSAGE_DATA:
| Code: |
Enumeration<Object> e = pcfm.getParameters();
byte[] b = null;
while (e.hasMoreElements()) {
Object element = e.nextElement();
if (String.valueOf(element).contains("MQBACF_MESSAGE_DATA")) {
// instantiate b here
}
}
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The reason I do a get twice for a grpHeader parameter is because directly seeking the bytes parameter value will error out if the parameter does not exist, whereas the generic getParameterValue() method will return null. This is behavior I experienced last year on MQ8. It might be fixed by current versions, so it will be worth looking into again for the performance gains you mentioned. |
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