org.apache.felix.dm.annotation.api

Annotation Type AspectService

@Retention(value=CLASS)
 @Target(value=TYPE)
public @interface AspectService

Annotates an Aspect service. Aspects allow you to define an interceptor, or chain of interceptors for a service (to add features like caching or logging, etc ...). The dependency manager intercepts the original service, and allows you to execute some code before invoking the original service ... The aspect will be applied to any service that matches the specified interface and filter and will be registered with the same interface and properties as the original service, plus any extra properties you supply here. If you declare the original service as a member it will be injected.

For "add", "change", "remove" callbacks, the following method signatures are supported:

 (Component comp, ServiceReference ref, Service service)
 (Component comp, ServiceReference ref, Object service)
 (Component comp, ServiceReference ref)
 (Component comp, Service service)
 (Component comp, Object service)
 (Component comp)
 (Component comp, Map properties, Service service)
 (ServiceReference ref, Service service)
 (ServiceReference ref, Object service)
 (ServiceReference ref)
 (Service service)
 (Service service, Map propeerties)
 (Map properties, Service, service)
 (Service service, Dictionary properties)
 (Dictionary properties, Service service)
 (Object service)
 

For "swap" callbacks, the following method signatures are supported:

 (Service old, Service replace)
 (Object old, Object replace)
 (ServiceReference old, Service old, ServiceReference replace, Service replace)
 (ServiceReference old, Object old, ServiceReference replace, Object replace)
 (Component comp, Service old, Service replace)
 (Component comp, Object old, Object replace)
 (Component comp, ServiceReference old, Service old, ServiceReference replace, Service replace)
 (Component comp, ServiceReference old, Object old, ServiceReference replace, Object replace)
 (ServiceReference old, ServiceReference replace)
 (Component comp, ServiceReference old, ServiceReference replace)
 

Usage Examples

Here, the AspectService is registered into the OSGI registry each time an InterceptedService is found from the registry. The AspectService class intercepts the InterceptedService, and decorates its "doWork()" method. This aspect uses a rank with value "10", meaning that it will intercept some other eventual aspects with lower ranks. The Aspect also uses a service property (param=value), and include eventual service properties found from the InterceptedService:

 
 @AspectService(ranking=10))
 class AspectService implements InterceptedService {
     // The service we are intercepting (injected by reflection)
     volatile InterceptedService intercepted;
   
     public void doWork() {
        intercepted.doWork();
     }
 }
 

Required Element Summary

Required Elements

Modifier and Type	Required Element and Description
int	ranking Sets the ranking of this aspect.

Optional Element Summary

Optional Elements

Modifier and Type	Optional Element and Description
java.lang.String	added The callback method to be invoked when the original service is available.
java.lang.String	changed The callback method to be invoked when the original service properties have changed.
java.lang.String	factoryMethod Sets the static method used to create the AspectService implementation instance.
java.lang.String	field Sets the field name where to inject the original service.
java.lang.String	filter Sets the filter condition to use with the service interface this aspect is applying to.
Property[]	properties Deprecated. you can apply Property annotation directly on the component class.
java.lang.String	removed The callback method to invoke when the service is lost.
ServiceScope	scope The service scope for the service of this Component.
java.lang.Class<?>	service Sets the service interface to apply the aspect to.
java.lang.String	swap name of the callback method to invoke on swap.

Element Detail

ranking

public abstract int ranking

Sets the ranking of this aspect. Since aspects are chained, the ranking defines the order in which they are chained. Chain ranking is implemented as a service ranking so service lookups automatically retrieve the top of the chain.

Returns:

the aspect service rank

service

public abstract java.lang.Class<?> service

Sets the service interface to apply the aspect to. By default, the directly implemented interface is used.

Returns:

the service aspect

Default:

java.lang.Object.class

filter

public abstract java.lang.String filter

Sets the filter condition to use with the service interface this aspect is applying to.

Returns:

the service aspect filter

Default:

""

properties

public abstract Property[] properties

Deprecated. you can apply Property annotation directly on the component class.

Sets Additional properties to use with the aspect service registration

Returns:

the aspect service properties.

Default:

{}

field

public abstract java.lang.String field

Sets the field name where to inject the original service. By default, the original service is injected in any attributes of the aspect implementation that are of the same type as the aspect interface.

Returns:

the field used to inject the original service

Default:

""

added

public abstract java.lang.String added

The callback method to be invoked when the original service is available. This attribute can't be mixed with the field attribute.

Returns:

the add callback

Default:

""

changed

public abstract java.lang.String changed

The callback method to be invoked when the original service properties have changed. When this attribute is used, then the added attribute must also be used.

Returns:

the changed callback

Default:

""

removed

public abstract java.lang.String removed

The callback method to invoke when the service is lost. When this attribute is used, then the added attribute must also be used.

Returns:

the remove callback

Default:

""

swap

public abstract java.lang.String swap

name of the callback method to invoke on swap.

Returns:

the swap callback

Default:

""

factoryMethod

public abstract java.lang.String factoryMethod

Sets the static method used to create the AspectService implementation instance. The default constructor of the annotated class is used. The factoryMethod can be used to provide a specific aspect implements, like a DynamicProxy.

Returns:

the aspect service factory method

Default:

""

scope

public abstract ServiceScope scope

The service scope for the service of this Component.

If not specified, the singleton service scope is used.

Default:

org.apache.felix.dm.annotation.api.ServiceScope.SINGLETON