class PathMapper implements Mapper {

    @Override
    public Object keyForSource(RowProxy source) {

        // if source does not contain a key, we must fail, otherwise multiple
        // rows will be incorrectly matched against NULL key

        try {
            return source.get(dbPath);
        }
        catch (IllegalArgumentException e) {
            throw new LmRuntimeException("Source does not contain key path: " + dbPath);
        }
    }

    public  PathMapper(String dbPath);

}