ActiveMQ Composite Destinations

Composite queue allows one-to-many relationship. Send a message to One Queue (A) and it will forward the message to Queue B, Queue C and Topic D.

To map Composite destination you need to add following section in virtualDestinations tag.

 <destinationInterceptors>

    <virtualDestinationInterceptor>

        <virtualDestinations>

<compositeQueue name="TEST.QUEUE.A">

   <forwardTo>

<queue physicalName="TEST.QUEUE.B" />

<queue physicalName="TEST.QUEUE.C" />

<queue physicalName="TEST.TOPIC.D" />

   </forwardTo>

</compositeQueue>

        </virtualDestinations>

    </virtualDestinationInterceptor>

  </destinationInterceptors>

By default, subscribers cannot consume messages directly from a composite queue or topic - it is a logical construct only. Given the configuration above, subscribers can only consume messages from TEST.QUEUE.B, TEST.QUEUE.C and TEST.TOPIC.D; but NOT TEST.QUEUE.A.

Using filtered destinations

You may wish to create a virtual destination which forwards messages to multiple destinations but applying a selector first to decide if the message really does have to go to a particular destination.

 <destinationInterceptors>

    <virtualDestinationInterceptor>

        <virtualDestinations>

<compositeQueue name="TEST.QUEUE.A">

   <forwardTo>

<filteredDestination selector="criteria = ‘B’” queue="TEST.QUEUE.B" />

<filteredDestination selector="criteria = ‘C’” queue="TEST.QUEUE.C" />

<filteredDestination selector="criteria = ‘D’” queue="TEST.TOPIC.D" />

   </forwardTo>

</compositeQueue>

        </virtualDestinations>

    </virtualDestinationInterceptor>

  </destinationInterceptors>

In the case above, message from TEST.QUEUE.A will be forwarded to filtered destinations with selector criteria. Result is same as having selector based consumer on TEST.QUEUE.B

Important Aspects of Composite Destinations:

-          Listener Queues (under forwardTo Tag) will not be created automatically. If queues are not present, message will be LOST.

-          If you want to store message in composite queue, make forwardOnly flag as ‘false’. It’s true by default.

<compositeQueue name="TEST.QUEUE.A" forwardOnly="false">   

      <forwardTo>

<queue physicalName="TEST.QUEUE.B" />

   </forwardTo>

</compositeQueue>

-          Composite queue can send the message to Virtual Topic, which will be further consumed by multiple Virtual Destinations.

-          Virtual Topic Selector Aware Consumers will not pull the message if consumer is not active; On the contrary, Filtered Composite destinations pull the message despite of consumer’s active status. This is very helpful in real world scenarios.

-          Important: Composite Destinations Supports wildcards. This is also valid for Filtered Destinations.

<destinationInterceptors>

   <virtualDestinationInterceptor>

      <virtualDestinations>

<compositeQueue name="TEST.QUEUE.A">

<forwardTo>

   <filteredDestination selector="criteria = ‘B’” queue="TEST.B.>."/>

   <queue physicalName="COMPOSITE.WILD.>."/>

</forwardTo>

</compositeQueue>

</virtualDestinations>

</virtualDestinationInterceptor>

</destinationInterceptors>

In the settings above, message will be forwarded to all the queues starting with “COMPOSITE.WILD”. Also, the message with filtered destinations will be forwarded to all the queues starting with ‘TEST.B’.