org.apache.felix.ipojo.util
Class Tracker

java.lang.Object
  extended by org.apache.felix.ipojo.util.Tracker
All Implemented Interfaces:
TrackerCustomizer

public class Tracker
extends java.lang.Object
implements TrackerCustomizer

Utility class close to the OSGi Service Tracker. This class is used when tracking dynamic services is required.

Author:
Felix Project Team

Field Summary
protected  org.osgi.framework.BundleContext m_context
          Bundle context against which this Tracker object is tracking.
protected  TrackerCustomizer m_customizer
          TrackerCustomizer object for this tracker.
protected  org.osgi.framework.Filter m_filter
          Filter specifying search criteria for the services to track.
protected  java.lang.String m_listenerFilter
          Filter string for use when adding the ServiceListener.
 
Constructor Summary
Tracker(org.osgi.framework.BundleContext context, org.osgi.framework.Filter filter, TrackerCustomizer customizer)
          Create a Tracker object on the specified Filter object.
Tracker(org.osgi.framework.BundleContext context, org.osgi.framework.ServiceReference reference, TrackerCustomizer customizer)
          Create a Tracker object on the specified ServiceReference object.
Tracker(org.osgi.framework.BundleContext context, java.lang.String clazz, TrackerCustomizer customizer)
          Create a Tracker object on the specified class name.
 
Method Summary
 void addedService(org.osgi.framework.ServiceReference reference)
          Default implementation of the TrackerCustomizer.addedService method.
 boolean addingService(org.osgi.framework.ServiceReference reference)
          Default implementation of the TrackerCustomizer.addingService method.
 void close()
          Close this Tracker object.
 java.lang.Object getService()
          Returns a service object for one of the services being tracked by this Tracker object.
 java.lang.Object getService(org.osgi.framework.ServiceReference reference)
          Returns the service object for the specified ServiceReference object if the referenced service is being tracked by this Tracker object.
 org.osgi.framework.ServiceReference getServiceReference()
          Returns a ServiceReference object for one of the services being tracked by this Tracker object.
 org.osgi.framework.ServiceReference[] getServiceReferences()
          Return an array of ServiceReference objects for all services being tracked by this Tracker object.
 java.util.List getServiceReferencesList()
          Get the list of stored service reference.
 java.lang.Object[] getServices()
          Return an array of service objects for all services being tracked by this Tracker object.
 java.util.List getUsedServiceReferences()
          Return the list of references used by the tracker.
 void modifiedService(org.osgi.framework.ServiceReference reference, java.lang.Object service)
          Default implementation of the TrackerCustomizer.modifiedService method.
 void open()
          Open this Tracker object and begin tracking services.
 void remove(org.osgi.framework.ServiceReference reference)
          Remove a service from this Tracker object.
 void removedService(org.osgi.framework.ServiceReference reference, java.lang.Object service)
          Default implementation of the TrackerCustomizer.removedService method.
 int size()
          Return the number of services being tracked by this Tracker object.
 void ungetService(org.osgi.framework.ServiceReference reference)
          Unget the given service reference.
 java.lang.Object waitForService(long timeout)
          Wait for at least one service to be tracked by this Tracker object.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

m_context

protected org.osgi.framework.BundleContext m_context
Bundle context against which this Tracker object is tracking.


m_filter

protected org.osgi.framework.Filter m_filter
Filter specifying search criteria for the services to track.


m_customizer

protected TrackerCustomizer m_customizer
TrackerCustomizer object for this tracker.


m_listenerFilter

protected java.lang.String m_listenerFilter
Filter string for use when adding the ServiceListener. If this field is set, then certain optimizations can be taken since we don't have a user supplied filter.

Constructor Detail

Tracker

public Tracker(org.osgi.framework.BundleContext context,
               org.osgi.framework.ServiceReference reference,
               TrackerCustomizer customizer)
Create a Tracker object on the specified ServiceReference object. The service referenced by the specified ServiceReference object will be tracked by this Tracker.

Parameters:
context - BundleContext object against which the tracking is done.
reference - ServiceReference object for the service to be tracked.
customizer - The customizer object to call when services are added, modified, or removed in this Tracker object. If customizer is null, then this Tracker object will be used as the TrackerCustomizer object and the Tracker object will call the TrackerCustomizer methods on itself.

Tracker

public Tracker(org.osgi.framework.BundleContext context,
               java.lang.String clazz,
               TrackerCustomizer customizer)
Create a Tracker object on the specified class name. Services registered under the specified class name will be tracked by this Tracker object.

Parameters:
context - BundleContext object against which the tracking is done.
clazz - Class name of the services to be tracked.
customizer - The customizer object to call when services are added, modified, or removed in this Tracker object. If customizer is null, then this Tracker object will be used as the TrackerCustomizer object and the Tracker object will call the TrackerCustomizer methods on itself.

Tracker

public Tracker(org.osgi.framework.BundleContext context,
               org.osgi.framework.Filter filter,
               TrackerCustomizer customizer)
Create a Tracker object on the specified Filter object.

Services which match the specified Filter object will be tracked by this Tracker object.

Parameters:
context - BundleContext object against which the tracking is done.
filter - Filter object to select the services to be tracked.
customizer - The customizer object to call when services are added, modified, or removed in this Tracker object. If customizer is null, then this Tracker object will be used as the TrackerCustomizer object and the Tracker object will call the TrackerCustomizer methods on itself.
Method Detail

open

public void open()
Open this Tracker object and begin tracking services.

Services which match the search criteria specified when this Tracker object was created are now tracked by this Tracker object.


close

public void close()
Close this Tracker object.

This method should be called when this Tracker object should end the tracking of services.


addingService

public boolean addingService(org.osgi.framework.ServiceReference reference)
Default implementation of the TrackerCustomizer.addingService method.

This method is only called when this Tracker object has been constructed with a null TrackerCustomizer argument. The default implementation returns the result of calling getService, on the BundleContext object with which this Tracker object was created, passing the specified ServiceReference object.

This method can be overridden in a subclass to customize the service object to be tracked for the service being added. In that case, take care not to rely on the default implementation of removedService that will unget the service.

Specified by:
addingService in interface TrackerCustomizer
Parameters:
reference - Reference to service being added to this Tracker object.
Returns:
The service object to be tracked for the service added to this Tracker object.
See Also:
TrackerCustomizer

addedService

public void addedService(org.osgi.framework.ServiceReference reference)
Default implementation of the TrackerCustomizer.addedService method.

Specified by:
addedService in interface TrackerCustomizer
Parameters:
reference - added reference.
See Also:
TrackerCustomizer.addedService(org.osgi.framework.ServiceReference)

modifiedService

public void modifiedService(org.osgi.framework.ServiceReference reference,
                            java.lang.Object service)
Default implementation of the TrackerCustomizer.modifiedService method.

This method is only called when this Tracker object has been constructed with a null TrackerCustomizer argument. The default implementation does nothing.

Specified by:
modifiedService in interface TrackerCustomizer
Parameters:
reference - Reference to modified service.
service - The service object for the modified service.
See Also:
TrackerCustomizer

removedService

public void removedService(org.osgi.framework.ServiceReference reference,
                           java.lang.Object service)
Default implementation of the TrackerCustomizer.removedService method.

This method is only called when this Tracker object has been constructed with a null TrackerCustomizer argument. The default implementation calls ungetService, on the BundleContext object with which this Tracker object was created, passing the specified ServiceReference object.

This method can be overridden in a subclass. If the default implementation of addingService method was used, this method must unget the service.

Specified by:
removedService in interface TrackerCustomizer
Parameters:
reference - Reference to removed service.
service - The service object for the removed service.
See Also:
TrackerCustomizer

waitForService

public java.lang.Object waitForService(long timeout)
                                throws java.lang.InterruptedException
Wait for at least one service to be tracked by this Tracker object.

It is strongly recommended that waitForService is not used during the calling of the BundleActivator methods. BundleActivator methods are expected to complete in a short period of time.

Parameters:
timeout - time interval in milliseconds to wait. If zero, the method will wait indefinately.
Returns:
Returns the result of getService().
Throws:
java.lang.InterruptedException - If another thread has interrupted the current thread.

getServiceReferences

public org.osgi.framework.ServiceReference[] getServiceReferences()
Return an array of ServiceReference objects for all services being tracked by this Tracker object.

Returns:
Array of ServiceReference objects or null if no service are being tracked.

getServiceReferencesList

public java.util.List getServiceReferencesList()
Get the list of stored service reference.

Returns:
the list containing used service reference

getUsedServiceReferences

public java.util.List getUsedServiceReferences()
Return the list of references used by the tracker. A reference becomes used when the dependency has already call getService on this reference.

Returns:
: the list of used references.

getServiceReference

public org.osgi.framework.ServiceReference getServiceReference()
Returns a ServiceReference object for one of the services being tracked by this Tracker object. If multiple services are being tracked, the service with the highest ranking (as specified in its service.ranking property) is returned. If there is a tie in ranking, the service with the lowest service ID (as specified in its service.id property); that is, the service that was registered first is returned. This is the same algorithm used by BundleContext.getServiceReference.

Returns:
ServiceReference object or null if no service is being tracked.
Since:
1.1

getService

public java.lang.Object getService(org.osgi.framework.ServiceReference reference)
Returns the service object for the specified ServiceReference object if the referenced service is being tracked by this Tracker object.

Parameters:
reference - Reference to the desired service.
Returns:
Service object or null if the service referenced by the specified ServiceReference object is not being tracked.

ungetService

public void ungetService(org.osgi.framework.ServiceReference reference)
Unget the given service reference.

Parameters:
reference - : service reference to unget.

getServices

public java.lang.Object[] getServices()
Return an array of service objects for all services being tracked by this Tracker object.

Returns:
Array of service objects or null if no service are being tracked.

getService

public java.lang.Object getService()
Returns a service object for one of the services being tracked by this Tracker object.

If any services are being tracked, this method returns the result of calling getService(getServiceReference()).

Returns:
Service object or null if no service is being tracked.

remove

public void remove(org.osgi.framework.ServiceReference reference)
Remove a service from this Tracker object. The specified service will be removed from this Tracker object. If the specified service was being tracked then the TrackerCustomizer.removedService method will be called for that service.

Parameters:
reference - Reference to the service to be removed.

size

public int size()
Return the number of services being tracked by this Tracker object.

Returns:
Number of services being tracked.