Looking for a specific MsgID on a Queue.get()

[jsaenz]

Hi everybody,

I have a problem reading from a queue to get a message with an specific ID. My platform MQSeries5.2.1 using Java.

The issue i want to resolve is: I put a message on a queue1 to query a database, then, a server listening prgm. is reading the queue1, getting the message's text to query a database and return the resultet putting a message on a queue2. So, the client who made the query petition on a queue1, is reading the queue2 to seek for the message that contains the resultet. (In all process, i'm storing the messageId and correlationID trough MQMD Message Descriptor)

The problem is when i look for the message id on a queue2 i always get the first message on the queue

//my client code is pretty much like this....

class myClass{
private MQMD msgDef = new MQMD();

//Put message on queue1
private void putMessage(String pstrQry){
MQMessage msgPut = new MQMessage();
msgPut.messageType = MQC.MQMT_DATAGRAM;
msgPut.format = MQC.MQFMT_STRING;
msgDef.messageId = msgPut.messageId;
msgDef.correlationId = msgPut.correlationId;
msgPut.writeString(pstrQry);
putOptions.options = MQC.MQPMO_NEW_MSG_ID | MQC.MQPMO_NEW_CORREL_ID | MQC.MQPMO_FAIL_IF_QUIESCING;
qEnvio.put(msgPut, putOptions);
}

//Get message on queue2
private String getMessage(){
MQGetMessageOptions getMsgOpt = new MQGetMessageOptions();
getMsgOpt.options = MQC.MQGMO_WAIT | MQC.MQGMO_FAIL_IF_QUIESCING;
getMsgOpt.waitInterval = 15000;
getMsgOpt.matchOptions = MQC.MQMO_MATCH_MSG_ID | MQC.MQMO_MATCH_CORREL_ID;
MQMessage msgFromQueue = new MQMessage();
msgFromQueue.messageId = msgDef.messageId;
msgFromQueue.correlationId = msgDef.correlationId;
qRespuesta.get(msgFromQueue, getMsgOpt);
strRespuesta = msgFromQueue.readString(msgFromQueue.getMessageLength());
}
}

//Note i always store the MessageID and CorrelationID using a Message Descriptor using code...
private MQMD msgDef = new MQMD();



What could be the problem??
I have to specify others Put or Get MessageOptions??

I hope you can help me!

 

[GFC]

Some points:
i) You seem to have saved MsgId and CorrelId BEFORE the

qEnvio.put(msgPut, putOptions);

which generates a MsgId and CorrelId because you specify

putOptions.options = MQC.MQPMO_NEW_MSG_ID |
MQC.MQPMO_NEW_CORREL_ID |
MQC.MQPMO_FAIL_IF_QUIESCING;


The MsgId and CorrelId sent with the message will not be what was saved earlier. I would expect that what you see is a reply to msg1 when you expect reply for msg2 (i.e. always 1 msg out-of-step).

Try moving
msgDef.messageId = msgPut.messageId;
msgDef.correlationId = msgPut.correlationId;

after
qEnvio.put(msgPut, putOptions);


ii) In request/reply, you probably should use MQC.MQFMT_REQUEST and MQC.MQFMT_REPLY instead of MQC.MQFMT_DATAGRAM.

iii) A better use of MsgId and CorrelId is to have the server application assign the original (client's) MsgId into the CorrelId of the reply and allow MQ generate a unique MsgId. This ensures unique MsgId (by QMgr) for all messages. The client application will request match on CorrelId using the MsgId that MQ generated for the .put