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

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>

Libertylibia

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

Sardine

One thing BalusC, is it possible to "select"/view the status that a question has as default (for example when you are editing a question then you have already set the status of the question to something) – Libertylibia

In the above example, JSF will do it by default when #{bean.question.status} has a valid enum value. You don't need to do anything expect of ensuring that the question has the proper status property prefilled. – Sardine

@Sardine How to access ordinal value from JSF? – Nona

If, like me, you get a number format exception for += status, then try using .concat(status) as @Ziletka suggests. – Restrainer

If you prefer java.util.List you can just modify getStatuses() return type to List<Status> and return Arrays.asList(Status.values()); – Igal

Due to inheritance (in my case) JSF isn't able to detect the target type as an enum. Is there a way to force JSF to convert the value? – Clypeate

If I want to control the labels of the selectOneMenu 's items with something like: <f:selectItems value="#{receiptController.allPaymentTypes()}" var="paymentType" itemValue="#{paymentType}" itemLabel="#{msg[paymentType.i18nKey]}" /> by msg is my message bundle and i18nKey is an all-uppercase key in my message bundle. – Hydracid

How does it happend that <f:selectItems value="#{Status}" /> is calling Status.values(). Why is it sufficient and why do you prefer it over <f:selectItems value="#{Status.values()}" />. Thanks :-) – Shadowy

@FabianBarney Click the link behind <o:importConstants> to learn about its working. – Sardine

I did not find the answer to my question on that page. Furthermore I did not find the answer why you prefer <f:selectItems value="#{Status}" /> over <f:selectItems value="#{Status.values()}" />. I was just interested in your personal preferences and why you choose the one way over the other. But no problem. – Shadowy

The Primefaces library also has the <p:importEnum> tag – Freeness

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.

Durkheim

Note that this syntax is only supported since EL 2.2 which is "relatively" new. Otherwise you can always grab <c:set> or <ui:param> or homebrew a custom EL function. – Sardine

Thank you BalusC. Is it possible to somehow replace #{data.statuses} with enum Class, without using backing bean (e.g. value="#{org.myproject.Status.values}")? – Durkheim

@Sardine are you sure? I'm using GF 3.1.2 (Mojarra JSF 2.1.6). – Durkheim

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).

Meanly

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)

Length

No need for a "function" (method more), when you can use #{myBundle[enumName.i18nKey]} and then put the i18n keys into your enumeration as properties: BLA_TYPE("SOME_BLA_TYPE_KEY") by BLA_TYPE is the enum to be used and SOME_BLA_TYPE_KEY is the i18n key. – Hydracid