code: protected final <E extends Object> E getService(Class<E> serviceType){
  	ServiceReference<E> ref = getServiceReference(serviceType);
  	if(ref == null){
  	    ref = context.getServiceReference(serviceType);
  	    references.put(serviceType, ref);
  	}
  	return context.getService(ref);
      }
docs: This method will retrieve a service from the service registry, and remember the reference, so it can be closed after {@code doLoad returns}.
  
  @param <E>
  @param serviceType The service type for which to retrieve an instance.
  @return A service of the type defined by {@code serviceType}