// Find the list of Cells that support the given extension. If none,
// then throw an exception.
CellRegistry registry = CellRegistry.getCellRegistry();
Set<CellFactorySPI> factorySet = registry.getCellFactoriesByExtension(extension);
if (factorySet == null || factorySet.size() == 0) {
throw new CellCreationException();
}
// If there is only one, then just return it, since there is no choices
// to be made.
if (factorySet.size() == 1) {