code: @Nullable
    public static DefaultEntityResolver createOnDemand (@Nonnull final IReadableResource aBaseResource)
    {
      final URL aURL = aBaseResource.getAsURL ();
      return aURL == null ? null : new DefaultEntityResolver (aURL);
    }
docs: Factory method with a resource.
  
  @param aBaseResource
  The base resource. May not be <code>null</code>.
  @return <code>null</code> if the resource does not exist