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h1. Configuration Handler

_The configuration handler aims to manage component configuration. This handler allows the 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. iPOJO also supports complex properties composed by maps, dictionaries, lists and arrays._

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h2. Configurable Properties

To 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.

h2. Examples

{code:xml}
<iPOJO>
<Component className="fr.imag.adele.escoffier.hello.impl.HelloServiceImpl">
   <Provides>
       <Property name="foo" field="m_foo"/>
   </Provides>
   <Properties propagation="false"/>
       <Property name="foo" field="m_foo"/>
       <Property name="array" method="updateArray"/>
       <Property 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>
{code}
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 neither field nor method is attached to this property.

These three properties are configured by the instance configuration.

By setting the attribute *propagation* 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 properties contained in the configuration are propagated to the service registrations. For example, in the previous example, not only {{foo}} will be published but {{array}} and {{hello.language}} are also published.
If a property has a method, this method is invoked each time that the property value changes (the method is called to push the initial value just after the constructor). The method receives one argument of the type of the property (an integer array in the example).

h2. Exposing a Managed Service
The ManagedService is a service specified in the OSGi Compendium. It allows reconfiguring an instance with the Configuration Admin. There is two way for an iPOJO instance to expose a Managed Service.
* In the component type description by adding the {{pid}} attribute in the properties element 
* In the instance configuration by configuring the {{managed.service.pid}} property
{code:xml}
<iPOJO>
<Component className="fr.imag.adele.escoffier.hello.impl.HelloServiceImpl">
   <Provides>
       <Property name="foo" field="m_foo"/>
   </Provides>
   <Properties propagation="false" pid="mymanagedservicepid"/>
       <Property name="foo" field="m_foo"/>
       <Property name="array" method="updateArray"/>
       <Property 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"/>
   <property name="managed.service.pid" value="mymanagedservicepid2"/>
</instance>
</iPOJO>
{code}
{info:title=Type vs. Instance configuration}
If the managed service pid is specified both in the component type and in the instance configuration, the instance configuration is used.
{info}

The managed service pid is the identifier used by the Configuration Admin to attach configuration to Managed Services. First this pid must be unique (as any pid in OSGi). Moreover, this pid cannot be the same one that the pid used in the Managed Service Factory to create the instance (if you use this way to create your instance).

When an instance is reconfigured with the Managed Service, the configuration is propagated if the propagation is enabled.

h2. Dynamic Reconfiguration using Factories or ManagedServiceFactories
The handler supports reconfiguration. To reconfigure an instance you can use both iPOJO Factory and the ManagedServiceFactory exposed by the factory of the targeted instance. By calling the method _reconfigure_ or _update_ (according of the service do you use), the handler receive the new configuration and apply it. If the propagation is activated, the service registrations are updated too.

h2. Being notified when a reconfiguration is completed
Sometimes you need to be notified when a reconfiguration is done (all setter method called). This can be done thanks to the {{updated}} attribute. This attribute specifies a method claeed when a configuration/reconfiguration is completed. This method receives a {{Dictionary}} containing the properties (pair <key,value>). Properties with no value are not in the received configuration.

{code:xml}
<Component className="...HelloServiceImpl">
   <Provides>
       <Property name="foo" field="m_foo"/>
   </Provides>
   <Properties updated="afterReconfiguration"/>
       <Property name="foo" field="m_foo"/>
       <Property name="array" method="updateArray"/>
       <Property name="hello.language" type="java.lang.String"/>
   </Properties>
</Component>
{code}

{code:java}
public void afterReconfiguration(Dictionary config) {
  ...
}
{code}
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