Finding the reason code in a dead-letter message using IBM MQ classes for Java

In this example, the read method populates the MQDLH object by reading from the message. After the read operation, the message read cursor is positioned immediately after the MQDLH header content.

Messages on the queue manager's dead-letter queue are prefixed with a dead-letter header (MQDLH). To decide how to handle these messages - for example, to determine whether to retry or discard them - a dead-letter handling application must look at the reason code contained in the MQDLH.

import com.ibm.mq.MQMessage;
import com.ibm.mq.headers.MQDLH;
...
MQMessage message = ... // Message received from the dead-letter queue.
MQDLH dlh = new MQDLH ();

dlh.read (message);

System.out.println ("Reason: " + dlh.getReason ());

All header classes also provide a convenience constructor to initialize themselves directly from the message in a single step. So the code in this example could be simplified as follows:

import com.ibm.mq.MQMessage;
import com.ibm.mq.headers.MQDLH;
...
MQMessage message = ... // Message received from the dead-letter queue.
MQDLH dlh = new MQDLH (message);

System.out.println ("Reason: " + dlh.getReason ());