Apache Camel with IBM MQ

Question

Hello has anyone ever used Camel with IBM\'s MQ. We are looking at possibly using the two products together but have no example of the two products working together.

Answer 1

The best I have been able to get is documented below, illustrated as a Spring XML application context that itself hosts the CAMEL context and routes. This sample works with the IBM native MQ JCA-compliant resource adapter v7.5, CAMEL 2.16, Spring core 4.2. I have deployed it in Glassfish, Weblogic, and JBoss EAP7 servers.

The complexity is bound to handling the flow of MQ reports whose philosophy conflicts with that of a plain JMS reply-to message. For a detailed explanation, please refer to Implementing native websphere MQ with CoD over Camel JMS component

This example based on the CAMEL XML DSL is self-contained and easy to test.

We start with Spring & CAMEL declarations:

The CAMEL context follows with 2 routes: MQ to JMS and JMS to MQ, here chained to form a bridge to ease testing.

Weird: on Weblogic, the only way to get (e.g.) 3 listeners is to enforce 3 connections (with 3 Camel:from statements in sequence) with max 1 session each, otherwise an MQ error ensues: MQJCA1018: Only one session per connection is allowed. On JBoss, you can simply adjust concurrentConsumers=...

The disable disableReplyTo option above ensures that CAMEL will not produce a reply before we can test the MQ message type to be 1=Request(-reply) or 8=datagram (one way!). That test and reply construction is not illustrated here.

Then we enforce the EIP to InOnly on the next posting to plain JMS to be consistent with the Inbound MQ mode.

This ends the MQ-to-jms route; next comes the jms-to-MQ route still in the same CAMEL context:

Now comes the request flag for the MQ CoD report to be returned by remote destination. We also enforce the MQ message to be of Datagram type (value 8).

  2048
  64
  8

The ReplyTo queue can be specified either via the ReplyTo uri option, else as a header as below.

Next we do use CamelJmsDestinationName header to enforce suppressing of the JMS MQ message header MQRFH2 (using targetClient MQ URL option value 1). In other words, we want to send a plain vanilla MQ binary message (i.e. Only the MQMD message descriptor followed by the payload).

  TEST.REPLYTOQ
   queue://MYQMGR/TEST.Q2?targetClient=1

More MQMD fields may be controlled through reserved JMS properties as illustrated below. See restrictions in IBM doc.

  MQSTR   
  _PLACEHOLDER_24_CHARS_ID_

The destination queue in the URI is overwritten by the CamelJmsDestinationName above, hence the queue name in the URI becomes a placeholder.

The URI option preserveMessageQos is the one that - as observed - allows sending a message with the ReplyTo data being set (to get the MQ CoD Report), yet prevent CAMEL to instantiate a Reply message listener by enforcing the InOnly MEP.

We have not finished, we have still to declare our queue factories for both a native JMS provider and Websphere MQ (via the native IBM WMQ JCA Resource Adapter), to be adjusted to your context. We use here JNDI lookups on administrative objects.

An alternative to fetching the factories (and JCA adapters) from JNDI is to declare the JMS client as Spring beans. In Weblogic and Glassfish, you'll be better inspired by deploying the native IBM JCA resource adapter and creating JNDI resources then referenced in the Spring Context as above, in JBoss a direct MQ client bean declaration suits best as below)

Comments and improvements welcome.