Internationalization

Internationalization (i18n) refers to designing a software application to support multiple languages and regions without engineering changes. In Spring MVC, this is done by externalizing messages and making the application flexible to adapt to different locales.

Concepts

• LocaleResolver: The LocaleResolver determines the locale (language/region) based on the user’s request. Spring provides two common implementations:
  • SessionLocaleResolver: Stores the locale in the session.
  • CookieLocaleResolver: Stores the locale in a cookie.
• MessageSource: The MessageSource is responsible for reading messages from property files. These files contain language-specific translations, and Spring automatically loads them based on the current locale.

Setting up i18n in Spring MVC

• Define Message Source: Create property files for different locales. For example:
  • messages.properties (default)
  • messages_fr.properties (French)
  • messages_es.properties (Spanish)

• Configure LocaleResolver: In your Spring configuration, define a LocaleResolver bean. For example:

  1 2 3 4

  @Bean public LocaleResolver localeResolver() {     return new SessionLocaleResolver(); }

• Configure MessageSource: Define a MessageSource bean that loads the properties files.

  1 2 3 4 5 6 7

  @Bean public MessageSource messageSource() {     ResourceBundleMessageSource messageSource = new ResourceBundleMessageSource();     messageSource.setBasename("messages");     messageSource.setDefaultEncoding("UTF-8");     return messageSource; }

• Locale Change Interceptor: You can allow users to change the language dynamically by using a LocaleChangeInterceptor. Add the following configuration to intercept changes:

  1 2 3 4 5 6

  @Bean public LocaleChangeInterceptor localeChangeInterceptor() {     LocaleChangeInterceptor interceptor = new LocaleChangeInterceptor();     interceptor.setParamName("lang");     return interceptor; }

• Using Messages in Views: In your views (JSP or Thymeleaf), you can reference these messages with the ${messages} tag:

  1	<h1>${messages['welcome.message']}</h1>

• Handling Different Locales: When users visit your application, they can either be served content in the default language or based on their selected locale, allowing for dynamic translation without any code changes.

Advantages of Internationalization

• Global Reach: Make your app accessible to users worldwide by supporting multiple languages.
• Seamless Experience: Users can interact with your application in their preferred language.
• Maintenance: Update translations without affecting the application code.