IBM MQ Message Listener

Question

Hi does anyone know how to create a message listener using IBM MQ? I know how to do it using the JMS spec but I am not sure how to do it for IBM MQ. Any links or pointers are greatly appreciated.

Answer 1

Although there is a WMQ Java API as noted by the previous responders, WMQ supports JMS as well so here are some resources to get you started there.

Take a look at this article: IBM WebSphere Developer Technical Journal: Running a standalone Java application on WebSphere MQ V6.0

Also, if you have installed the full WMQ client and not just grabbed the jars then you will have lots of sample code installed. By default, these will live in C:\Program Files\IBM\WebSphere MQ\tools\jms or /opt/mqm/samp depending on your platform.

If you need the WMQ Client install media, get it here. Note that this is the WMQ v7 client and not the v6 client. It is compatible with the v6 QMgr but since v6 is end-of-life as of September 2011 you should be doing new development on the v7 client and, if possible, a v7 QMgr. There are a lot of functional and performance enhancements available if both sides are v7.

You can get the product manual here if you need it.

Finally, please be sure when you get a JMS exception to print the linked exception. This is not a WMQ thing, rather it's a JMS thing. Sun provided a multi-level data structure for JMS exceptions and the really interesting parts are often in the nested level. This is not a big deal and can be implemented in a few lines:

try {
  .
  . code that might throw a JMSException
  .
} catch (JMSException je) {
  System.err.println("caught "+je);
  Exception e = je.getLinkedException();
  if (e != null) {
    System.err.println("linked exception: "+e);
  } else {
    System.err.println("No linked exception found.");
  }
}

This helps to determine the difference between a JMS error versus a transport error. For example a JMS security error might be a WMQ 2035, or it might be the JSSE configuration, or the app might not have access to something in the file system. Only one of these is worth spending a lot of time digging through the WMQ error logs for and only by printing the linked exception will you be able to tell if it's that one.