10 Internationalization - Reference Documentation
Authors: Graeme Rocher, Peter Ledbrook, Marc Palmer, Jeff Brown, Luke Daley, Burt Beckwith
Version: 1.3.9
Table of Contents
10 Internationalization
Grails supports Internationalization (i18n) out of the box through the underlying Spring MVC support for internationalization. With Grails you are able to customize the text that appears in any view based on the users Locale. To quote the javadoc for the Locale class in Java:A Locale object represents a specific geographical, political, or cultural region. An operation that requires a Locale to perform its task is called locale-sensitive and uses the Locale to tailor information for the user. For example, displaying a number is a locale-sensitive operation--the number should be formatted according to the customs/conventions of the user's native country, region, or culture.A Locale is made up of a language code and a country code. For example "en_US" is the code for US english, whilst "en_GB" is the for British English.
10.1 Understanding Message Bundles
Now that you have an idea of locales, to take advantage of them in Grails you have to create message bundles that contain the different languages that you wish to render. Message bundles in Grails are located inside thegrails-app/i18n directory and are simple Java properties files.Each bundle starts with the name messages by convention and ends with the locale. Grails ships with a bunch of built in message bundles for a whole range of languages within the grails-app/i18n directory. For example:messages.properties messages_de.properties messages_es.properties etc.
messages.properties for messages, unless the user has specified a custom locale. You can create your own message bundle by simply creating a new properties file that ends with the locale you are interested. For example messages_en_GB.properties for British English.
10.2 Changing Locales
By default the user locale is detected from the incomingAccept-Language header. However, you can provide users the capability to switch locales by simply passing a parameter called lang to Grails as a request parameter:/book/list?lang=es
10.3 Reading Messages
Reading Messages in the View
The most common place that you need messages is inside the view. To read messages from the view just use the message tag:<g:message code="my.localized.content" />messages.properties (with appropriate locale suffix) such as the one below then Grails will look-up the message:my.localized.content=Hola, Me llamo John. Hoy es domingo.
message tag:<g:message code="my.localized.content" args="${ ['Juan', 'lunes'] }" />my.localized.content=Hola, Me llamo {0}. Hoy es {1}.Reading Messages in Controllers and Tag Libraries
Since you can invoke tags as methods from controllers it is also trivial to read messages within in a controller:def show = {
def msg = message(code:"my.localized.content", args:['Juan', 'lunes'])
}g. prefix:def myTag = { attrs, body ->
def msg = g.message(code:"my.localized.content", args:['Juan', 'lunes'])
}10.4 Scaffolding and i18n
Grails does not ship with i18n aware scaffolding templates to generate the controller and views. However, i18n aware templates are available via the i18n templates plugin. The templates are identical to the default scaffolding templates, except that they are i18n aware using the message tag for labels, buttons etc.To get started install the i18n templates with the following command:grails install-plugin i18n-templates