Selecting from a list of entities

See http://docs.jboss.org/seam/latest/reference/en/html/controls.html

• Use <s:selectItems> to produce a list of labeled select items from a list of entities.
• Use <s:convertEntity> to map back and forth between the select items and the actual entity values. This is what allows you to map the value of the <h:selectOneMenu> directly to the property of the referencing entity (e.g. a property that is a many-to-one).

1. person is an entity that has been outjected into the conversation. It has a 'continent' property which is many-to-one association with another entity.
2. continents is a Seam application framework 'query' object. This 'query' object should probably use a Seam-managed EntityManager because we want have the Hibernate session-in-view behavior so we don't get lazy initialization exceptions when rendering the labels, etc.
3. s:convertEntity will convert the Continent entities into values for the HTML select, and vice versa.

Tips

1. To avoid LazyInitializationExceptions and/or writing extra code in your EJB/Controller bean to initialize objects, use session in view.
2. For required fields, put required="true" on the selectOneMenu and override javax.faces.component.UIInput.REQUIRED in messages.properties (see Standard Faces Error Messages).

Select from an enum

This works just like selecting an entity, but <s:convertEnum/> is used instead.

XHTML:

EnumLists.java:

1. person is an entity that has been outjected into the conversation. It has a 'status' property which is an enum.
2. We need to expose the values of the enum as a list or an array, so we make a stateless POJO component with getters that returns arrays for various enums called enumLists.

Multi-select from an enum

Here we use a selectManyCheckbox.

The enumLists.roleArray method simply returns the list of all possible Role values from the enum:

The Person object might be an Entity with a set of enum Role values, mapped to a simple table as strings (see Hibernate JPA Tips - Collection of primitives):

Unfortunately, Seam's convertEnum can't handle multi selects yet. This example will yield a strange exception:

Luckily, it's very easy to create Custom converter tags with Facelets. Here is the converter class that handles both ordinary enums and multi-selects: