Internationalization (I18n)

Are you ready to localize your web application into additional languages? This guide will walk you through the localization (i18N) support available in Micro and will teach you how to internationalize a Micro application right from the start. In Micro the localization support is implemented as an extension and it is an optional feature enabled by default.

Getting started / La mise en route / Einstieg

First make sure you have the i18n extension loaded in the system. The configuration file is in config/extensions/i18N.yml, and it looks like this:

#alias: L10n
class: ca.simplegames.micro.extensions.i18n.I18NExtension
intercept: {parameter_name: locale, scope: "session, request, context"}
default_encoding: utf-8
resource_cache: 10
base_names: [config/locales/messages]

This file is instructing Micro about the following aspects:

  • intercept - declares a parameter with a name defined by the user: locale in this case, parameter that can be transmitted through any of these Micro components: session, request or context. For example, the links:, will use the French language_Country localization for displaying the about/index.html page.
  • default_encoding - the encoding used by the i18N extension. We encourage you to leave it as is: utf-8, respectively. Read more about encoding here.
  • resource_cache - how many seconds the localization properties will be cached before reloading the definitions.
  • base_names - the location and name prefix for the properties files containing the translated text. With this configuration, Micro will load properties from the following files: config/locales/ or config/locales/ for English, config/locales/ for German, and so on.

The properties file names contain a language and an optional country ISO code, allowing you to fine tune the translation; i.e. currencies, date format, etc.

Second, verify that the i18N extension is required by your application. You can do that by simply adding few lines of code in the config/application.bsh startup controller. Example of enabling the i18N extension:

excerpt from the config/application.bsh file:


If successfully loaded, Micro will display a simple startup message when the application is instantiated. Look for these messages in your server log:

INFO ... .micro.SiteContext - Extensions:
INFO ... .micro.SiteContext -   i18N, loaded.

Localize your site

Say you have a web page that contains a some text that has to be presented in multiple languages, the: header.html, a page you want to include and reuse in your templates. We will use the Velocity template language for the next few examples. This is the initial version of the header.html, its static version:


  <p>Hello World!</p>

Now let's spice it up with some dynamic content.


Where #i18N is a Velocity macro provided by Micro to help you write cleaner i18N code in your views. The #i18N expects a key (or a list with keys) that will be used to look up the translation in the properties files; in this case the key being: hello_world.

Translate the hello_world key in the following languages and store them in the appropriate properties files in the config/locales/ folder. Example.

        path              | language |    content
--------------------------|----------|-----------------------------------    | English  | hello_world=Hello World!    | French   | hello_world=Bonjour tout le monde!    | German   | hello_world=Hallo Welt! | German   | hello_world=grüezi!    | Greek    | hello_world=γειά σου κόσμος

You don't have to restart the Micro web application, the changes will be available right away. Visit your page containing the header.html and you should see:

<p>Bonjour tout le monde!</p>   

for a page where you specified the French language as a request parameter: http://localhost/index.html?locale=fr or this:

<p>Hallo Welt!</p>

if the request parameter was specifying the German language: http://localhost/index.html?locale=de, and:


for a request specifying the Switzerland country and German language localization: http://localhost/index.html?locale=de_CH

There is a full example in the Micro examples repository at Github, see the Hello World web application for how the i18N support is used.

Success / Bonne chance! / ¡buena suerte

Have fun localizing your site!

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