Building an index for OSGi service properties

gistfile1.java

public class IndexingTracker extends ServiceTracker {
	
	private final ConcurrentMap<Object, ServiceReference> index = new ConcurrentHashMap<Object, ServiceReference>();
	
	private final String keyProperty;

	public IndexingTracker(BundleContext context, String serviceClass, String keyProperty) {
		super(context, serviceClass, null);
		this.keyProperty = keyProperty;
	}
	
	@Override
	public Object addingService(ServiceReference reference) {
		Object id = reference.getProperty(keyProperty);
		ServiceReference existing = index.putIfAbsent(id, reference);
		if (existing != null) {
			// TODO: what should happen if multiple services have the same key?
		}
		return id;
	}
	
	@Override
	public void removedService(ServiceReference reference, Object id) {
		index.remove(id);
	}
	
	public ServiceReference findByKey(Object key) {
		return index.get(key);
	}
}

// Example use:
IndexingTracker indexer = new IndexingTracker(context, MyService.class.getName(), "ID");
indexer.open();