Utility classes originally included in the CustomField add-on or its source code repository. These include classes related to conversions (including those between a bean or entity and its identifier for one-to-one, one-to-many and many-to-many relations) and validation as well as a composite item class and related conversion and formatting helpers. The CustomField add-on (https://vaadin.com/directory#addon/customfield) is required by some of these utility classes.