Localization

A TranslatableComponent carries a key instead of text. The vanilla client resolves keys it knows against its own language files, so Component.translatable("block.minecraft.stone") will show up as "Stone" if the player's language is set to English.

Keys the client does not know are resolved server-side. Adventure's GlobalTranslator does this from a ResourceBundle per locale:

ResourceBundle bundle = ResourceBundle.getBundle("messages", Locale.US);
TranslationStore.StringBased<MessageFormat> store = TranslationStore.messageFormat(Key.key("minestom:messages"));
store.registerAll(Locale.US, bundle, true);
GlobalTranslator.translator().addSource(store);

player.sendMessage(Component.translatable("minestom.welcome"));

Automatic translation

Minestom can render every outgoing component against the receiving player's locale. This is disabled by default and controlled by ServerFlag#AUTOMATIC_COMPONENT_TRANSLATION, read from the minestom.automatic-component-translation system property:

-Dminestom.automatic-component-translation=true

WARNING

The flag is read once and cannot be changed at runtime. Setting the system property from code has no effect unless it happens before the server is initialized.

When enabled, components in outgoing packets are passed through MinestomAdventure#COMPONENT_TRANSLATOR, which defaults to GlobalTranslator::render. Replace it to translate through something other than Adventure's registry:

MinestomAdventure.COMPONENT_TRANSLATOR = (component, locale) -> myTranslator.render(component, locale);

Players that have not sent a locale use MinestomAdventure#getDefaultLocale(), which is the JVM default until changed:

MinestomAdventure.setDefaultLocale(Locale.US);

Serializing translated text

The plain text, legacy, and ANSI serializers use Minestom's component flattener, which resolves translation keys through COMPONENT_TRANSLATOR at the default locale.

WARNING

The flattener only does this when automatic translation is enabled. With the flag off, which is the default, a TranslatableComponent contributes nothing at all to the flattened string: not the translation, not the key, not the fallback. Enable the flag, or resolve the component yourself before serializing it.