Page History

...

The configuration handler aims to manage component configuration. This handler allows the OSGi configuration admin to push a configuration to create, destroy or update configuration and dynamic reconfiguration of instances. A configuration is a set of couple (name, value). The name can be a field name or a property name associated to a field or/and a method.

Configurable Property configuration

Not all instances are configurable. A component type sets its configurable properties by adding in this metadata a ConfigurableProperty elementTo support configuration, the component type needs to declare which properties are configurable. These properties are not necessarily service property but can be internal component property. Moreover, there are not declared inside a Provides element but directly under the Component element.

Examples

<iPOJO>
<Component className="fr.imag.adele.escoffier.hello.impl.HelloServiceImpl">
   <Provides>
       <Property name="foo" field="m_foo"/>
   </Provides>
   <Properties configurable="truefalse"/>
          <Property name="foo" field="m_foo"/>
          <Property name="array" fieldmethod="my_arrayupdateArray"/>
          <Properties name="hello.language" type="java.lang.String"/>
   </Properties>
</Component>

<instance component="fr.imag.adele.escoffier.hello.impl.HelloServiceImpl" name="HelloService">
   <property name="foo" value="bar"/>
   <property name="array" value="\{1, 2, 3}"/>
   <property name="hello.language" value="en"/>
</instance
</iPOJO>

In the previous snippet, you can see three configurable properties. The first is a configurable property attached to the field 'foo' that is a service property too. The second is an array property attached to a method (updatArray). The third property is a static property, in the sense that no neither field nor method is attached to this property.

These three properties are configured by the instance configuration.

The By setting the attribute configurable= to "true", you allow the property propagation to the service registration. It means that at each time that  the configuration of the instance is updated, all property contained in the configuration is propagate to the service registrations. For example, in the previous example, not only foo will be published but array and hello.lanaguage too.allows the exposition of the ManagedService service. Therefore, when a new configuration is pushed, the published service properties changes too. The configuration admin uses the name of the instance to know which configuration is associated with which component instance. The name needs to be unique for the framework.

Technical Explanations

This handler has two capacity :

• first, pushing instance configuration to the component instance
• and allowing the dynamic configuration of these properties

If a property has a method, this method in invoke each time that the proeprty value changes. The method receive one argument of the type of the property (int array int the example).

Dynamic Reconfiguration

The handler supports reconfiguration. To reconfigure an instance you can use both iPOJO Factory and the ManagedServiceFactory exposed by the factory of the targetted instance. By calling the method reconfigure or update (according of the service do you use), the handler receive the new configuratino and apply it. If the propagation is activated, the service registratinos are updated tooThe second point is not enable by default. To enable it, the attribute configurable need to be true. Then the handlers provides the "org.osgi.service.cm.ManagedService" service. Therefore, the configuration admin looks for all this services and manages (push or update) configurations to the components.
When the configuration admin push a configuration to a component, the configurable property value change but it diffuses the change to service property if needed.