Translate the options of a choice

Choice components, such as DropDownChoice, RadioChoice, ListChoice and CheckBoxMultipleChoice, show the display value of each choice as it is. To show it in the user’s language, look the display value up as a key, or render enum values through an EnumChoiceRenderer.

Use the display values as keys

Override localizeDisplayValues() to return true. The choice component then treats each display value as a key:

PreferencesPage.java

List<String> colors = List.of("green", "red", "blue", "yellow");

add(new DropDownChoice<>("color", colorModel, colors) {
    @Override
    protected boolean localizeDisplayValues() {
        return true;
    }
});

PreferencesPage.properties

green=Green
red=Red
blue=Blue
yellow=Yellow

PreferencesPage_de.utf8.properties

green=Grün
red=Rot
blue=Blau
yellow=Gelb

For each option, Wicket first tries the key <component id>.<display value>, here color.green, and then green. When neither exists, it shows the display value itself. The value that is submitted does not change; only the text the user sees is translated.

Translate enum values

For an enum, use an EnumChoiceRenderer. It looks up the key <enum class simple name>.<constant name>:

public enum Size { SMALL, MEDIUM, LARGE }

add(new DropDownChoice<>("size", sizeModel, List.of(Size.values()),
    new EnumChoiceRenderer<>(this)));

Size.SMALL=Small
Size.MEDIUM=Medium
Size.LARGE=Large

Pass a component to the constructor, usually the page or panel, so that its bundles are searched. Without one, the renderer only looks in application-wide bundles. Unlike localizeDisplayValues, a missing key is an error, so every constant needs a text. Override resourceKey(T) to use other keys.

Change the text of the empty option

A DropDownChoice shows an extra option when it has no selection yet, by default “Choose One”. When setNullValid(true) makes no selection a valid choice, the extra option is always there and is empty by default. Both texts are looked up like other texts:

color.null=Pick a color
size.nullValid=No preference

null=... without an id in the application bundle changes the text for every drop-down in the application.

These keys work whether or not the display values are translated. The lookup of each key follows the usual order, described in Where Wicket looks for texts. The choice components themselves are listed in Form components.