Package org.apache.axis2.transport.base.tracker

Class AxisServiceTracker

java.lang.Object

org.apache.axis2.transport.base.tracker.AxisServiceTracker

public class AxisServiceTracker
extends Object

Tracks services deployed in a given AxisConfiguration. The tracker is configured with references to three objects:

1. An AxisConfiguration to watch.
2. An AxisServiceFilter restricting the services to track.
3. An AxisServiceTrackerListener receiving tracking events.

An instance of this class maintains an up-to-date list of services satisfying all of the following criteria:

1. The service is deployed in the given AxisConfiguration.
2. The service is started, i.e. AxisService.isActive() returns true.
3. The service matches the criteria specified by the given AxisServiceFilter instance.

Whenever a service appears on the list, the tracker will call AxisServiceTrackerListener.serviceAdded(AxisService). When a service disappears, it will call AxisServiceTrackerListener.serviceRemoved(AxisService).

When the tracker is created, it is initially in the stopped state. In this state no events will be sent to the listener. It can be started using start() and stopped again using stop(). The tracker list is defined to be empty when the tracker is in the stopped state. This implies that a call to start() will generate AxisServiceTrackerListener.serviceAdded(AxisService) events for all services that meet the above criteria at that point in time. In the same way, stop() will generate AxisServiceTrackerListener.serviceRemoved(AxisService) events for the current entries in the list.

As a corollary the tracker guarantees that during a complete lifecycle (start-stop), there will be exactly one AxisServiceTrackerListener.serviceRemoved(AxisService) event for every AxisServiceTrackerListener.serviceAdded(AxisService) event and vice-versa. This property is important when the tracker is used to allocate resources for a dynamic set of services.

Limitations

The tracker is not able to detect property changes on services. E.g. if a service initially matches the filter criteria, but later changes so that it doesn't match the criteria any more, the tracker will not be able to detect this and the service will not be removed from the tracker list.

Constructor Summary

Constructors

Constructor	Description
AxisServiceTracker(AxisConfiguration config, AxisServiceFilter filter, AxisServiceTrackerListener listener)

Method Summary

Modifier and Type	Method	Description
boolean	isStarted()	Check whether the tracker is started.
void	start()	Start the tracker.
void	stop()	Stop the tracker.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

AxisServiceTracker

public AxisServiceTracker(AxisConfiguration config,
                          AxisServiceFilter filter,
                          AxisServiceTrackerListener listener)

Method Detail

isStarted

public boolean isStarted()

Check whether the tracker is started.

Returns:

true if the tracker is started

start

public void start()

Start the tracker.

Throws:

IllegalStateException - if the tracker has already been started

stop

public void stop()

Stop the tracker.

Throws:

IllegalStateException - if the tracker is not started