How to use enum values in f:selectItem(s) - jsf

Question

I want to make a selectOneMenu dropdown so I can select a status on my question. Is it possible to make the f:selectItem more flexible considering what happens if the order of the enums changes, and if the list was large? And could I do this better? And is it possible to automatically "select" the item that the question have?
Enum class
public enum Status {
SUBMITTED,
REJECTED,
APPROVED
}
Question entity
#Enumerated(EnumType.STRING)
private Status status;
JSF
<div class="field">
<h:outputLabel for="questionStatus" value="Status" />
<h:selectOneMenu id="questionStatus" value="#{bean.question.status}" >
<f:selectItem itemLabel="Submitted" itemValue="0" />
<f:selectItem itemLabel="Rejected" itemValue="1" />
<f:selectItem itemLabel="Approved" itemValue="2" />
</h:selectOneMenu>
<hr />
</div>

Answer 1

JSF has a builtin converter for enum, so this should do:
#Named
#ApplicationScoped
public class Data {
public Status[] getStatuses() {
return Status.values();
}
}
with
<h:selectOneMenu value="#{bean.question.status}" >
<f:selectItems value="#{data.statuses}" />
</h:selectOneMenu>
(note: since JSF 2.0 there's no need anymore to provide a SelectItem[] or List<SelectItem>, a T[] and List<T> are accepted as well and you can access the current item by var attribute)
If you happen to use JSF utility library OmniFaces, then you could use <o:importConstants> instead of a bean.
<o:importConstants type="com.example.Status" />
<h:selectOneMenu value="#{bean.question.status}" >
<f:selectItems value="#{Status}" />
</h:selectOneMenu>
If you intend to control the labels as well, you could add them to the Status enum:
public enum Status {
SUBMITTED("Submitted"),
REJECTED("Rejected"),
APPROVED("Approved");
private String label;
private Status(String label) {
this.label = label;
}
public String getLabel() {
return label;
}
}
with
<f:selectItems value="#{data.statuses}" var="status"
itemValue="#{status}" itemLabel="#{status.label}" />
Or, better, make the enum value a property key of a localized resource bundle (EL 3.0 required):
<f:selectItems value="#{data.statuses}" var="status"
itemValue="#{status}" itemLabel="#{text['data.status.' += status]}" />
with this in a properties file associated with resource bundle #{text}
data.status.SUBMITTED = Submitted
data.status.REJECTED = Rejected
data.status.APPROVED = Approved

Answer 2

For localization we can use also this solution:
public enum Status { SUBMITTED, REJECTED, APPROVED }
data.status.SUBMITTED=Submitted
data.status.REJECTED=Rejected
data.status.APPROVED=Approved
<h:selectOneMenu value="#{bean.question.status}" >
<f:selectItems
value="#{data.statuses}"
var="status"
itemValue="#{status}"
itemLabel="#{text['data.status.'.concat(status)]}" />
</h:selectOneMenu>
So the resource path for localization strings are not hardcoded in Enum.

Answer 3

You could use <f:selectItems value="#{carBean.carList}" /> and return a list of SelectItem instances that wrap the enum (use Status.values() to get all possible values).

Answer 4

You can use following utility el function to obtain the enum values and use them in a SelectOneMenu for example. No need to create beans and boilerplate methods.
public final class ElEnumUtils
{
private ElEnumUtils() { }
/**
* Cached Enumerations, key equals full class name of an enum
*/
private final static Map<String, Enum<?>[]> ENTITY_ENUMS = new HashMap<>();;
/**
* Retrieves all Enumerations of the given Enumeration defined by the
* given class name.
*
* #param enumClassName Class name of the given Enum.
*
* #return
*
* #throws ClassNotFoundException
*/
#SuppressWarnings("unchecked")
public static Enum<?>[] getEnumValues(final String enumClassName) throws ClassNotFoundException
{
// check if already cached - use classname as key for performance reason
if (ElEnumUtils.ENTITY_ENUMS.containsKey(enumClassName))
return ElEnumUtils.ENTITY_ENUMS.get(enumClassName);
final Class<Enum<?>> enumClass = (Class<Enum<?>>) Class.forName(enumClassName);
final Enum<?>[] enumConstants = enumClass.getEnumConstants();
// add to cache
ElEnumUtils.ENTITY_ENUMS.put(enumClassName, enumConstants);
return enumConstants;
}
}
Register it as an el function in a taglib file:
<function>
<description>Retrieves all Enumerations of the given Enumeration defined by the given class name.</description>
<function-name>getEnumValues</function-name>
<function-class>
package.ElEnumUtils
</function-class>
<function-signature>
java.lang.Enum[] getEnumValues(java.lang.String)
</function-signature>
</function>
And finally call it like:
<p:selectOneMenu value="#{bean.type}">
<f:selectItems value="#{el:getEnumValues('package.BeanType')}" var="varEnum"
itemLabel="#{el:getEnumLabel(varEnum)}" itemValue="#{varEnum}"/>
</p:selectOneMenu>
Similiar to BalusC answer you should be using a resource bundle with localized enum labels and for cleaner code you can also create a function like getEnumLabel(enum)