Package org.apache.felix.dm

Interface AspectComponent

All Superinterfaces:
Component
public interface AspectComponent extends Component
Interface used to configure the various parameters needed when defining a Dependency Manager aspect component. 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.

Usage Examples

Here is a sample showing a DatabaseCache aspect which is created each time a Database interface is registered in the registry. 
 
 public class Activator extends DependencyActivatorBase {
     &Override
     public void init(BundleContext context, DependencyManager dm) throws Exception {
         AspectComponent aspectComponent = createAspectComponent()
             .setAspect(Database.class, null, 10)
             .setImplementation(DatabaseCache.class);
         dm.add(aspectComponent);
     }
 }
 
 interface Database {
     String get(String key);
 }
 
 class DatabaseCache implements Database {
     volatile Database originalDatabase; // injected
     
     String get(String key) {
         String value = cache.get(key);
         if (value == null) {
             value = this.originalDatabase.get(key);
             store(key, value);
         }
         return value;
     }
     ... 
 }

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)

  • Method Details

    • setScope

      AspectComponent setScope(Component.ServiceScope scope)
      Sets the component scope.
      Specified by:
      setScope in interface Component
      Parameters:
      scope - the component scope (default=SINGLETON)
      Returns:
      this component

    • setImplementation

      AspectComponent setImplementation(Object implementation)
      Sets the implementation for this component. You can actually specify an instance you have instantiated manually, or a Class that will be instantiated using its default constructor when the required dependencies are resolved, effectively giving you a lazy instantiation mechanism. There are four special methods that are called when found through reflection to give you life cycle management options:
      1. init() is invoked after the instance has been created and dependencies have been resolved, and can be used to initialize the internal state of the instance or even to add more dependencies based on runtime state
      2. start() is invoked right before the service is registered
      3. stop() is invoked right after the service is unregistered
      4. destroy() is invoked after all dependencies are removed
      In short, this allows you to initialize your instance before it is registered, perform some post-initialization and pre-destruction code as well as final cleanup. If a method is not defined, it simply is not called, so you can decide which one(s) you need. If you need even more fine-grained control, you can register as a service state listener too.
      Specified by:
      setImplementation in interface Component
      Parameters:
      implementation - the implementation
      Returns:
      this component
      See Also:

    • add

      AspectComponent add(Dependency... dependencies)
      Adds dependency(ies) to this component, atomically. If the component is already active or if you add dependencies from the init method, then you should add all the dependencies in one single add method call (using the varargs argument), because this method may trigger component activation (like the ServiceTracker.open() method does).
      Specified by:
      add in interface Component
      Parameters:
      dependencies - the dependencies to add.
      Returns:
      this component

    • remove

      AspectComponent remove(Dependency d)
      Removes a dependency from the component.
      Specified by:
      remove in interface Component
      Parameters:
      d - the dependency to remove
      Returns:
      this component

    • add

      AspectComponent add(ComponentStateListener listener)
      Adds a component state listener to this component.
      Specified by:
      add in interface Component
      Parameters:
      listener - the state listener

    • remove

      AspectComponent remove(ComponentStateListener listener)
      Removes a component state listener from this component.
      Specified by:
      remove in interface Component
      Parameters:
      listener - the state listener

    • setInterface

      AspectComponent setInterface(String serviceName, Dictionary<?,?> properties)
      Sets the public interface under which this component should be registered in the OSGi service registry.
      Specified by:
      setInterface in interface Component
      Parameters:
      serviceName - the name of the service interface
      properties - the properties for this service
      Returns:
      this component

    • setInterface

      AspectComponent setInterface(String[] serviceNames, Dictionary<?,?> properties)
      Sets the public interfaces under which this component should be registered in the OSGi service registry.
      Specified by:
      setInterface in interface Component
      Parameters:
      serviceNames - the names of the service interface
      properties - the properties for these services
      Returns:
      this component

    • setInterface

      AspectComponent setInterface(Class<?> serviceName, Dictionary<?,?> properties)
      Sets the public interface under which this component should be registered in the OSGi service registry.
      Specified by:
      setInterface in interface Component
      Parameters:
      serviceName - the name of the service interface
      properties - the properties for this service
      Returns:
      this component

    • setInterface

      AspectComponent setInterface(Class<?>[] serviceNames, Dictionary<?,?> properties)
      Sets the public interfaces under which this component should be registered in the OSGi service registry.
      Specified by:
      setInterface in interface Component
      Parameters:
      serviceNames - the names of the service interface
      properties - the properties for these services
      Returns:
      this component

    • setAutoConfig

      AspectComponent setAutoConfig(Class<?> clazz, boolean autoConfig)
      Configures auto configuration of injected classes in the component instance. The following injections are currently performed, unless you explicitly turn them off:
      BundleContext
      the bundle context of the bundle
      ServiceRegistration
      the service registration used to register your service
      DependencyManager
      the dependency manager instance
      Component
      the component instance of the dependency manager
      Specified by:
      setAutoConfig in interface Component
      Parameters:
      clazz - the class (from the list above)
      autoConfig - false to turn off auto configuration

    • setAutoConfig

      AspectComponent setAutoConfig(Class<?> clazz, String instanceName)
      Configures auto configuration of injected classes in the component instance.
      Specified by:
      setAutoConfig in interface Component
      Parameters:
      clazz - the class (from the list above)
      instanceName - the name of the instance to inject the class into
      See Also:

    • setServiceProperties

      AspectComponent setServiceProperties(Dictionary<?,?> serviceProperties)
      Sets the service properties associated with the component. If the service was already registered, it will be updated.
      Specified by:
      setServiceProperties in interface Component
      Parameters:
      serviceProperties - the properties

    • setCallbacks

      AspectComponent setCallbacks(String init, String start, String stop, String destroy)
      Sets the names of the methods used as callbacks. These methods, when found, are invoked as part of the life cycle management of the component implementation. The dependency manager will look for a method of this name with the following signatures, in this order:
      1. method(Component component)
      2. method()
      Specified by:
      setCallbacks in interface Component
      Parameters:
      init - the name of the init method
      start - the name of the start method
      stop - the name of the stop method
      destroy - the name of the destroy method
      Returns:
      the component

    • setCallbacks

      AspectComponent setCallbacks(Object instance, String init, String start, String stop, String destroy)
      Sets the names of the methods used as callbacks. These methods, when found, are invoked on the specified instance as part of the life cycle management of the component implementation.

      See setCallbacks(String init, String start, String stop, String destroy) for more information on the signatures. Specifying an instance means you can create a manager that will be invoked whenever the life cycle of a component changes and this manager can then decide how to expose this life cycle to the actual component, offering an important indirection when developing your own component models.

      Specified by:
      setCallbacks in interface Component
      Returns:
      this component

    • setFactory

      AspectComponent setFactory(Object factory, String createMethod)
      Sets the factory to use to create the implementation. You can specify both the factory class and method to invoke. The method should return the implementation, and can use any method to create it. Actually, this can be used together with setComposition to create a composition of instances that work together to implement a component. The factory itself can also be instantiated lazily by not specifying an instance, but a Class.
      Specified by:
      setFactory in interface Component
      Parameters:
      factory - the factory instance or class
      createMethod - the name of the create method
      Returns:
      this component

    • setFactory

      AspectComponent setFactory(String createMethod)
      Sets the factory to use to create the implementation. You specify the method to invoke. The method should return the implementation, and can use any method to create it. Actually, this can be used together with setComposition to create a composition of instances that work together to implement a component.

      Note that currently, there is no default for the factory, so please use setFactory(factory, createMethod) instead.

      Specified by:
      setFactory in interface Component
      Parameters:
      createMethod - the name of the create method
      Returns:
      this component

    • setComposition

      AspectComponent setComposition(Object instance, String getMethod)
      Sets the instance and method to invoke to get back all instances that are part of a composition and need dependencies injected. All of them will be searched for any of the dependencies. The method that is invoked must return an Object[].
      Specified by:
      setComposition in interface Component
      Parameters:
      instance - the instance that has the method
      getMethod - the method to invoke
      Returns:
      this component

    • setComposition

      AspectComponent setComposition(String getMethod)
      Sets the method to invoke on the service implementation to get back all instances that are part of a composition and need dependencies injected. All of them will be searched for any of the dependencies. The method that is invoked must return an Object[].
      Specified by:
      setComposition in interface Component
      Parameters:
      getMethod - the method to invoke
      Returns:
      this component

    • setDebug

      AspectComponent setDebug(String label)
      Activate debug for this component. Informations related to dependency processing will be displayed using osgi log service, our to standard output if no log service is currently available.
      Specified by:
      setDebug in interface Component
      Parameters:
      label -

    • setAspect

      AspectComponent setAspect(Class<?> service, String filter, int ranking)
      Sets the service interface to apply the aspect to (required parameter)
      Parameters:
      service - the service interface to apply the aspect to
      filter - the filter condition to use with the service aspect interface (null if no filter)
      ranking - the level used to organize the aspect chain ordering
      Returns:
      this aspect parameter instance

    • setAspectField

      AspectComponent setAspectField(String autoConfig)
      Sets the aspect implementation field name where to inject original service (optional parameter). If not set or null, any field matching the original service will be injected.
      Parameters:
      autoConfig - the aspect implementation field name where to inject original service
      Returns:
      this aspect parameter instance

    • setAspectCallbacks

      AspectComponent setAspectCallbacks(String add, String change, String remove, String swap)
      Sets name of the callbacks method to invoke on add,change,remove, or swap callbacks (optional parameter).
      Parameters:
      add - name of the callback method to invoke on add
      change - name of the callback method to invoke on change
      remove - name of the callback method to invoke on remove
      swap - name of the callback method to invoke on swap
      Returns:
      this aspect parameter instance

    • setAspectCallbackInstance

      AspectComponent setAspectCallbackInstance(Object callbackInstance)
      Sets the instance to invoke the callbacks on (optional parameter). null means the callbacks will be invoked on the aspect implementation object.
      Parameters:
      callbackInstance - the instance to invoke the callbacks on
      Returns:
      this aspect parameter instance