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Apache Stanbol - Enhancement Engine Manager

Enhancement Engine Manager

The EnhancementEngineManager provides name based access to all active EnhancementEngines and their ServiceReferences. This interface is typically used by components that need to lookup EnhancementEngines based on their name. However the EngineTracker implementation can also be used to track specific EnhancementEngines.

EnhancementEngineManager interface

This is the Java API providing access to registered EnhancementEngines in the ways as described above. This interface includes the following methods:

/** Getter for all names with active engines */
getActiveEngineNames() : Set<String>
/** Getter for the ServiceReference to the engine 
    with a given name */
getReference(String name) : ServiceReference
/** Getter for all ServiceReferences to engines 
    with a given name sorted by service ranking */
getReferences(String name)
/** Getter for the engine with a given name */
+ getEngine(Stirng name) : EnhancementEngine
/** Getter for all engines with a given name sorted 
    by service ranking */
+ getEngines(String name) : List<EnhancementEngine>
/** Getter for an engine based on a service reference */
+ getEngine(ServiceReference ref) : EnhancementEgnie
/** Checks if there is an engine for the given name */
+ isEngine(String name) : boolean

There are two implementations of this interface available:

EnhancementEngineManager Service

This is an implementation of the EnhancementEngineManager interface that is registered as OSGI service. It can be used e.g. by using the @Reference annotation

EnhancementEngineManager engineManager

This service is provided by the "org.apache.stanbol.enhancer.enginemanager" module and is included in all Stanbol launchers.


This is an utility similar to the standard OSGI ServiceTracker which allows to track some/all EnhancementEngines. It also supports the usage of a ServiceTrackerCustomizer so that users of that utility can directly react to changes of tracked EnhancementEngines.

//track only "myEngine" and "otherEngine"
EnginesTracker tracker = new EnginesTracker(
    context, "myEngine","otherEngine");; //start tracking

//the tracker need to be closed if no longer needed
tracker = null;

For most users the EnhancementEngineManager service is sufficient and preferable. Direct use of the EngineTracker is only recommended if one needs only to track some specific engines and especially if one needs to get notified an changes of such engines.

The implementation of the WeightedChain is a good example for the intended usage of the EnginesTracker.