> Markdown version of [Custom I18N Provider](https://vaadin.com/docs/next/flow/i18n/custom-i18n-provider). Section index: [llms.txt](https://vaadin.com/docs/next/flow/llms.txt)

# Custom I18N Provider

The built-in `DefaultI18NProvider` loads translations from property files in `src/main/resources/vaadin-i18n/`. If you need more control — loading translations from a database, using a different file structure, or applying custom fallback logic — implement the `I18NProvider` interface.

## <a id="implementing-i18nprovider"></a>Implementing I18NProvider

The following example enables Finnish and English, with Finnish as the default. Translation files use the `translate` prefix (e.g., `translate.properties`, `translate_fi_FI.properties`, `translate_en_GB.properties`) and are loaded from the classpath (e.g., `src/main/resources/`):

```java
public class TranslationProvider implements I18NProvider {

    public static final String BUNDLE_PREFIX = "translate";

    public final Locale LOCALE_FI = new Locale("fi", "FI");
    public final Locale LOCALE_EN = new Locale("en", "GB");

    private List<Locale> locales = Collections
            .unmodifiableList(Arrays.asList(LOCALE_FI, LOCALE_EN));

    @Override
    public List<Locale> getProvidedLocales() {
        return locales;
    }

    @Override
    public String getTranslation(String key, Locale locale, Object... params) {
        if (key == null) {
            LoggerFactory.getLogger(TranslationProvider.class.getName())
                    .warn("Got lang request for key with null value!");
            return "";
        }

        final ResourceBundle bundle = ResourceBundle.getBundle(BUNDLE_PREFIX, locale);

        String value;
        try {
            value = bundle.getString(key);
        } catch (final MissingResourceException e) {
            LoggerFactory.getLogger(TranslationProvider.class.getName())
                    .warn("Missing resource", e);
            return "!" + locale.getLanguage() + ": " + key;
        }
        if (params.length > 0) {
            value = MessageFormat.format(value, params);
        }
        return value;
    }
}
```

## <a id="configuring-the-provider"></a>Configuring the Provider

For Spring Boot projects, annotate your provider with `@Component` and it’s automatically detected — no further configuration needed:

```java
@Component
public class TranslationProvider implements I18NProvider {
    // ...
}
```

CDI-based projects can use a similar approach with CDI beans.

For other setups, set the `i18n.provider` property to the fully qualified class name of your provider, either as a system property:

```terminal
mvn jetty:run -Dvaadin.i18n.provider=com.vaadin.example.ui.TranslationProvider
```

Or via the `@WebServlet` annotation:

```java
@WebServlet(urlPatterns = "/*", name = "slot", asyncSupported = true, loadOnStartup = 1,
   initParams = { @WebInitParam(name = "i18n.provider", value = "com.vaadin.example.ui.TranslationProvider") })
public class ApplicationServlet extends VaadinServlet {
}
```