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19.2. Using a Custom Destination Resolver

Overview

Destination resolvers are a part of the JMS technology Red Hat JBoss Fuse inherits from the Spring Framework. They convert string destination names into JMS Destination objects. For example, if you specify an endpoint's destination using the destinationName attribute, the endpoint will use a destination resolver to get the appropriate JMS Destination object. Destination resolvers are also used if a destination chooser returns a string and not a JMS Destination object.
Red Hat JBoss Fuse JMS endpoints default to using the DynamicDestinationResolver destination resolver provided by the Spring Framework. This destination resolver uses the standard JMS Session.createTopic() and Session.createQueue() methods to resolve destination names.
Red Hat JBoss Fuse JMS endpoints can also use the Spring Framework's JndiDestinationResolver destination resolver. This destination resolver uses the string destination name to perform a JNDI lookup for the JMS destination. If JMS destination is not returned from the JNDI lookup, the resolver resorts to dynamically resolving the destination name. For information on configuring and endpoint to use the JndiDestinationResolver destination resolver. See the section called “Configuring an endpoint to use a destination resolver”.

Implementing a destination resolver

Destination resolvers implement the org.springframework.jms.support.destination.DestinationResolver interface. The interface has a single method: resolveDestinationName().
The resolveDestinationName() method, whose signature shown in Example 19.5, “Destination Resolver Method”, takes three parameters: a JMS session, a destination name, and a boolean specifying if the destination is a JMS topic.[2] It returns a JMS destination that correlates to the provided destination name.

Example 19.5. Destination Resolver Method

Destination resolveDestinationName(Session session,
                                   String destinationName,
                                   boolean pubSubDomain)
    throws JMSException;
Example 19.6, “Simple Destination Resolver” shows a simple destination resolver implementation.

Example 19.6. Simple Destination Resolver

package com.widgetVendor.example;

import org.springframework.jms.support.destination.DestinationResolver;
import javax.jms.Destination;
import javax.jms.JMSException;
import javax.jms.Session;

public class widgetDestinationResolver implements DestinationResolver
{
 
  public Destination resolveDestinationName(Session session,
                                            String destinationName,
                                            boolean pubSubDomain)
  throws JMSException
  {
    if (pubSubDomain)
    {
      return session.createTopic(destinationName);
    }
    else
    {
      return session.createQueue(destinationName);
    }
  }
}

Configuring an endpoint to use a destination resolver

You can configure an endpoint to use a custom destination resolver in one of two ways. The recommended way is to configure the destination resolver as a bean and have the endpoint reference the destination resolver's bean. The other way is to explicitly include the destination resolver's configuration as a child of the endpoint.
As shown in Example 19.7, “Configuring a Destination Resolver with a Bean Reference”, configuring an endpoint's destination resolver using a bean reference is a two step process:
  1. Configure a bean element for your destination resolver.
  2. Add a destinationResolver attribute that references the destination resolver's bean to your endpoint.

Example 19.7. Configuring a Destination Resolver with a Bean Reference

<beans xmlns:jms="http://servicemix.apache.org/jms/1.0"
       ... >
  ...
  <jms:consumer service="my:widgetService"
                endpoint="jbiWidget"
                destinationName="widgetQueue"
                connectionFactory="#connectionFactory"
                destinationResolver="#widgetDestinationResolver" />
  <bean id="widgetDestinationResolver"
        class="com.widgetVendor.example.widgetDestinationResolver" />
  ...
</beans>
Example 19.8, “Explicitly Configuring a Destination Resolver” shows an example configuration using the jms:destinationResolver element. This method is less flexible than the recommended method because other endpoints cannot reuse the destination resolver's configuration.

Example 19.8. Explicitly Configuring a Destination Resolver

<beans xmlns:jms="http://servicemix.apache.org/jms/1.0"
       ... >
  ...
  <jms:consumer service="my:widgetService"
                endpoint="jbiWidget"
                destinationName="widgetQueue"
                connectionFactory="#connectionFactory">
    <jms:destinationResolver>
      <bean id="widgetDestinationResolver"
            class="com.widgetVendor.example.widgetDestinationResolver" />
    </jms:destinationChooser>
  </jms:consumer>
  ...
</beans>

[2] If the value is false, a JMS queue will be returned.