CODEWITHSUNDEEP
stringobjectgetibm-mq
Nazim
Nazim

Reputation: 639

From C# after getting IBM MQ message how to identify message data type? Is it Object or String type?

In our company we are using IBM MQ server for message queueing. For the same queue we are putting both String and Object type data message with the help of methods WriteObject and WriteString.

The challenge is occured when it comes to consumption(read message) of queue. Since the Get data can be both Object or String we need to decide which method to use ReadString or ReadObject on the MQMessage instance. I made workaround like firstly using ReadObject method, if an exception occured then try it with ReadString.

I did not like this workaround, is there any way to identify message data type after calling MQQueue instance's Get method?

Here below you can find my workaround:

    public object GetMessage(string queueName) {

        MQQueueManager queueManager = new MQQueueManager("queueManagerName", "channel", "connection");
        MQGetMessageOptions queueGetMessageOptions = new MQGetMessageOptions();
        queueGetMessageOptions.Options = MQC.MQGMO_WAIT + MQC.MQGMO_FAIL_IF_QUIESCING + MQC.MQPMO_SYNCPOINT;

        try {
            queueRead = queueManager.AccessQueue(queueName, MQC.MQOO_INPUT_AS_Q_DEF + MQC.MQOO_FAIL_IF_QUIESCING);
            queueMessage = new MQMessage();
            queueMessage.Format = MQC.MQFMT_STRING;
            queueRead.Get(queueMessage, queueGetMessageOptions);

            try {
                var readObject = queueMessage.ReadObject();
                return readObject;
            } catch (SerializationException) { } // if message in queue not a object

            queueMessage.DataOffset = 0;
            var stringMsg = queueMessage.ReadString(queueMessage.MessageLength);
            return stringMsg;

        } catch (MQException exp) {                
            if (exp.ReasonCode != 2033) {
                log.ErrorFormat("MQException: ResonCode: {0}, {1}", exp.ReasonCode, exp.Message);                    
            }
        }
        return "";
    }

Upvotes: 0

Views: 2693

Answers (1)

Roger
Roger

Reputation: 7476

What a horrible design.

First off, why are you putting 2 different message types into the same queue? Bad, very bad idea. You should be using 2 different queues. What, does someone think queues are scarce or rare? You should be handing out queues like candy.

Secondly, if you really need to go with this design then you should read the MQ Knowledge Center on MQMD structure. It contains a field called 'Message Type'. Most applications use 'Message Type' to contain either 'MQMT_DATAGRAM' or 'MQMT_REQUEST' but you can set your own values starting with 'MQMT_APPL_FIRST'.

So, define a couple of constants:

public const int MY_MSG_OBJECT = MQC.MQMT_APPL_FIRST + 1;
public const int MY_MSG_STRING = MQC.MQMT_APPL_FIRST + 2;

Hence, the sending application putting a string message would do:

MQMessage sendmsg = new MQMessage();
sendmsg.Format = MQC.MQFMT_STRING;
sendmsg.MessageType = MY_MSG_STRING;
sendmsg.WriteString("This is a test message");
queue.Put(sendmsg, pmo);

and the sending application putting an object message would do:

MQMessage sendmsg = new MQMessage();
sendmsg.Format = MQC.MQFMT_NONE;
sendmsg.MessageType = MY_MSG_OBJECT;
sendmsg.WriteObject(someObject);
queue.Put(sendmsg, pmo);

The receiving application would do:

MQMessage rcvmsg = new MQMessage();
queue.Get(rcvmsg, gmo);
// Check the Message Type
if (rcvmsg.MessageType == MY_MSG_STRING)
{
   readString = queue.ReadString();
}
else if (rcvmsg.MessageType == MY_MSG_OBJECT)
{
   readObject = queue.ReadObject();
}
else
{
   System.Console.Out.WriteLine("Error: Unknown message type.");
}

Upvotes: 1

Related Questions