README.md

The Vaadin4Spring I18N Extensions

Internationalization in a Vaadin4Spring application is very much handled by the I18N features of Spring itself. However, to make it a bit easier to use, the addon provides a helper class, namely I18N.

The I18N can be injected into any Spring managed bean and uses the locale of the currently active UI when looking up messages from the application context.

Example:

 @Autowired
 I18N i18n; 
 ...
 myLabel = new Label(i18n.get("myMessageKey", "My argument"));

It is also possible to specify the Locale, when the bean creation happens before the UI is created.

Example:

 @Autowired
 I18N i18n; 
 ...
 myLabel = new Label(i18n.getWithLocale("myMessageKey", Locale.GERMAN, "My argument"));

Composite Message Source

A composite message source is an implementation of the Spring MessageSource interface that resolves messages by querying all beans in the application context that implement the MessageProvider interface.

The idea behind this is to make it possible to build modular UI applications that all share a single message source. Each module would have its own message provider, and would use either I18N or the application context directly to retrieve localized strings. The modules would be completely separated on a source code level, but during runtime they would all run inside a single application context.

Enabling the Composite Message Source

You can enable the composite message source by adding the @EnableCompositeMessageSource annotation to your Spring configuration. This will add the message source to your application context.

After this, create as many MessageProvider beans as you want. You can either implement the interface from scratch, or use the ResourceBundleMessageProvider. The latter reads messages from resource bundles with a specific basename and encoding (check the JavaDocs for more information).

Example

In the main application:

@EnableAutoConfiguration
@EnableCompositeMessageSource
@ComponentScan
@Configuration
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
    ...
}

In the UI module:

@Configuration
public class MyModule {
    @Bean
    MessageProvider communicationMessages() {
        return new ResourceBundleMessageProvider("mymodule.messages"); // Will use UTF-8 by default
    }
    ...
}

Finally a tip: If you are building a modular application, it is good practice to prepend the messages with some kind of module identifier, for example a Java package name. That way you can avoid naming conflicts when additional modules are added in the future.