Configuring an MDB to receive messages from ActiveMQ

There are three MDBs declared in the ejb-jar.xml deployment descriptor. For this example, I will be explaining how to configure the TopicDurableMDB to be invoked by JBoss when a message is received on an ActiveMQ Topic.

The Bean

In the ejb-jar.xml deployment descriptor, the TopicDurableMDB is declared as follows:

 
<message-driven>
   ...
   <ejb-name>TopicDurableMDB</ejb-name>
   <ejb-class>com.panacya.platform.service.bus.mdb.SimpleMessageReceiverBean</ejb-class>
   <messaging-type>javax.jms.MessageListener</messaging-type>
   ...
   <activation-config>
      <activation-config-property>
         <activation-config-property-name>Destination</activation-config-property-name>
         <activation-config-property-value>topic.testTopic</activation-config-property-value>
      </activation-config-property>
      <activation-config-property>
         <activation-config-property-name>DestinationType</activation-config-property-name>
         <activation-config-property-value>javax.jms.Topic</activation-config-property-value>
      </activation-config-property>
      ...
   </activation-config>
   ...
</message-driven>

The activation-config element and it's child element, activation-config-property, are new elements for EJBs, so you might not be familiar with them. I won't go into to much detail about them, but it is important to understand that this is the first mechanism you use to link an MDB to a JCA.

The Connector

The two activation-config-properties shown above link to the following elements in the ra.xml file, which is contained within the activemq-ra-1.2.rar file:

<inbound-resourceadapter>
      ...
         <activationspec>
            <activationspec-class>org.activemq.ra.ActiveMQActivationSpec</activationspec-class>
            <required-config-property>
               <config-property-name>Destination</config-property-name>
            </required-config-property>
            <required-config-property>
               <config-property-name>DestinationType</config-property-name>
            </required-config-property>
         </activationspec>
      ...
</inbound-resourceadapter>

In the ejb-jar.xml file section shown above, the value of the Destination property is set to topic.testTopic. This value is the physical name of the ActiveMQ destination the TopicDurableMDB will be receiving messages from and not a JNDI name. In other words, the value of the Destination property has no meaning to JBoss. It is purely an ActiveMQ setting.

The Glue

In JBoss, the thing which connects an inbound JMS destination to an MDB is a JBoss container. To use ActiveMQ as the inbound message source for the TopicDurableMDB we must configure a new JBoss container. We do this in the jboss.xml file.

Three things are needed in the jboss.xml file in order to tie an MDB to a connector. They are:

1. Configure a new invoker-proxy-binding that declares JBossMessageEndpointFactory as the proxy-factory
2. Configure a new MDB container which uses the new invoker-proxy-binding
3. Declare which MDBs should go into the new container

This first snippet configures a new invoker-proxy-binding:

<invoker-proxy-binding>
   <name>activemq-message-driven-bean</name>
   <invoker-mbean>default</invoker-mbean>
   <proxy-factory>org.jboss.ejb.plugins.inflow.JBossMessageEndpointFactory</proxy-factory>
   ...
</invoker-proxy-binding>

This second snippet configures a new MDB container which uses the invoker-proxy-binding configured above:

<container-configuration>
   <container-name>ActiveMQ Message Driven Bean</container-name>
   <call-logging>false</call-logging>
   <invoker-proxy-binding-name>activemq-message-driven-bean</invoker-proxy-binding-name>
   ...
</container-configuration>

This third snippet links the TopicDurableMDB to the activemq-ra-1.2.rar connector and tells JBoss to put instances of TopicDurableMDB into the new MDB container declared above:

<message-driven>
   <ejb-name>TopicDurableMDB</ejb-name>
   <resource-adapter-name>activemq-ra-1.2-SNAPSHOT.rar</resource-adapter-name>
   <configuration-name>ActiveMQ Message Driven Bean</configuration-name>
</message-driven>

The above examples highlight the key configuration settings needed to enable MDBs deployed in JBoss to process messages from an ActiveMQ destination.

You can try the above example, plus a few more, by downloading the activemq-jboss-test.zip file which contains the complete sample project.