OSGi Reference injection

 @Reference(referenceInterface = AspectRatioCalculator.class, cardinality = ReferenceCardinality.OPTIONAL_MULTIPLE, policy = ReferencePolicy.DYNAMIC)
    private final Map<String, AspectRatioCalculator> aspectRatioCalculators = new ConcurrentHashMap<String, AspectRatioCalculator>();

    protected void bindAspectRatioCalculators(final AspectRatioCalculator arc) {
        LOG.debug("Registering [{}] as aspect ratio calculator for resource type [{}]", arc.getClass().getName(), arc.getResourceType());
        this.aspectRatioCalculators.put(arc.getResourceType(), arc);
    }

    protected void unbindAspectRatioCalculators(final AspectRatioCalculator arc) {
        LOG.debug("Unregistering [{}] as aspect ratio calculator for resource type [{}]", arc.getClass().getName(), arc.getResourceType());
        this.aspectRatioCalculators.remove(arc.getResourceType());
    }