default Object getFieldValue(FacesContext context, UIColumn column) {
        return UIColumn.createValueExpressionFromField(context, getVar(), column.getField()).getValue(context.getELContext());
    }
Returns actives sort meta. See {@link SortMeta#compareTo(SortMeta)}
@return map with {@link SortMeta#getField()} as key and {@link SortMeta} as value
primefaces/src/main/java/org/primefaces/component/api/UITable.java