Creating OSGI Factory Configurations in AEM

AEM houses a powerful open-source framework in its technology stack, Apache Felix. Felix is an open-source implementation of OSGi. OSGi provides a way to manage bundles and their configurations.

OSGi provides a way to configure services and modify those configurations on the run-time. But apart from this, there is another powerful feature that OSGi provides that is: the ability to create Factory Configurations. Factory Configurations is a way to create a single service, and bind multiple configurations to it & then consume those configurations from different classes/Services. You all might have used Logger service provided by CQ out of the box, the logger is an example of a factory configuration service.

Here are the steps for how to create factory configuration in CQ.

Step 1:
Firstly create a Component/Service that holds configurations values. This component will act as an interface for adding properties of multiple configurations. The key to creating this Component/Service class is that declare this class as a configurationFactory and pass configuration policy as required. Here is the sample code :

@Component(label = "Factory configuration", immediate = true, enabled = true, 

metatype = true, 

description = "This is factory configuration which acts as a interface for allowing user to enter property values",

policy = ConfigurationPolicy.REQUIRE, configurationFactory = true)

@Property(name = "dummy.prop", label = "Dummy property", description = "This is just dummy property", value = "Dummy Value")

 public class FactoryConfig {      

      private static final Logger LOGGER = LoggerFactory.getLogger(FactoryConfig.class);      

      @Activate      

      public void activate(ComponentContext componentContext) {           

            Dictionary properties = componentContext.getProperties();        

            String dummyProperty = PropertiesUtil.toString(properties.get("dummy.prop"), "");

            LOGGER.info("Read the dummy property value : " + dummyProperty);

      }

Step 2:
Now that you have created the interface that takes input from the user, create a service that actually uses the FactoryConfig Component/Service to add configuration and accept values of properties. For creating this service we will use the dynamic binding of OSGi. We will have to create a collection of FactoryConfig class and binding & unbinding methods are also required that will add or remove each FactoryConfig object in/from the collections. 

@Component(label = 'Factory Congifuration', description = "", immediate = true, metatype = true, enabled = true)

@Service(FactoryConfigConsumer.class)

public class FactoryConfigConsumer {

@Reference(referenceInterface = FactoryConfig.class, 

cardinality = ReferenceCardinality.OPTIONAL_MULTIPLE,

policy = ReferencePolicy.DYNAMIC, name = "Code Brains Demo Factory configurations")

private List factoryConfigs;

     protected synchronized void bindFactoryConfig(final FactoryConfig config) {

          if (factoryConfigs == null) {

               factoryConfigs = new ArrayList<FactoryConfig>();

          }

          factoryConfigs.add(config);

     }

     protected synchronized void unbindFactoryConfig(final FactoryConfig config) {

          factoryConfigs.remove(config);

     }

}