Internationalize JSP-based Websites - JavaWorld March 2000
Tutorial Details:
Internationalize JSP-based Websites
Internationalize JSP-based Websites
By: By Govind Seshadri
Build Websites that speak in tongues
ypically, most Websites you come across are customized for a specific locale, with the locale defined as a geographical region or political entity that shares a common language, culture, and customs. While this may not be a significant issue to most people, it may pose some interesting challenges to those conducting business on the Web. By its very nature, ecommerce is all about facilitating commerce across national, linguistic, and cultural boundaries. While the Web may have opened up businesses to a truly international clientele, Web-based firms have to contend with the all-too-probable scenario of non-English-speaking users struggling to understand their sites' content. As many businesses have come to realize, every Web surfer who turns away because of the site's English-centric nature is a potential customer lost.
So, is there an easy, manageable solution to this problem that keeps you from having to run multiple versions of the site? Well, if the dynamic content for the Website is generated through Java technology, there sure is! That's because the Java platform intrinsically supports the development of locale-independent applications through various classes supporting internationalization found within the java.util , java.io , and java.text packages. Internationalization itself is the name given to the design process wherein an application's country, language, and culture-specific information is isolated and typically encapsulated within some external files or objects. Consequently, making your application compatible with an entirely new language or country does not have to involve a major rewrite of your presentation logic; rather, it now merely involves creating an additional version, specific to the new locale, of the external files. The process of creating these locale-specific entities (be they files or objects), along with the associated translation of text, is called localization .
Websites based on JavaServer Pages (JSPs) lend themselves more easily to internationalization than those developed using servlets. This is because the technology facilitates the separation of presentation from application logic. Now, let us examine this premise in detail by developing a global version of the Music Without Borders online store that was demonstrated in my earlier article on JSP architecture (see the Resources section below for a link to this story). The online store is based on the Model-View-Controller (MVC) architecture to maximize the separation of presentation from content.
Although internationalizing a JSP-based Web application is not particularly difficult, it is a task best initiated at the design stage. Toward this end, all locale-specific textual data that constitute an application's user interface, such as page headers and trailers, user messages, form button labels, dates, currencies, and so forth, are first identified and isolated from the application within external files. These entities, which hold different values under different locales, are also known as resources; a grouping of resources within an external class or property file is known as a resource bundle or, simply, a bundle.
The Java 2 SDK provides the abstract base class java.util.ResourceBundle for handling resources, along with its subclasses ListResourceBundle and PropertyResourceBundle . The bundle for a supported locale can be defined as either a classfile (by using ListResourceBundle ) or as a property file (by using PropertyResourceBundle ). Both these mechanisms then allow your application to access the values for resources by name, just as you would with a Hashtable object. Although you can store objects of any type as values for resources using classfiles, most Web applications use property files, since they almost always customize only string types. Consequently, I will focus my discussion on the use of property files.
Developing global Web applications
In this example, the Music Without Borders online store has been localized to support users not only in the US, but also in Germany, Sweden, and France. Listings 1 and 2 show the property files supporting the locales for the US and France. (You can obtain the property files for Germany and Sweden when you download the source code for the example in Resources .) As you can see, the property files essentially isolate all of the GUI elements from the JSP pages. The property files for bundles must follow some standard naming conventions. The suffix must always be properties . Also, since a locale is typically defined in Java via a country code and/or a language code and an optional variant, the name of the bundle has to correlate with the locale it serves. For instance, all of the following bundle prefixes are valid:
BundleName + "_" + localeLanguage + "_" + localeCountry + "_" + localeVariant
BundleName + "_" + localeLanguage + "_" + localeCountry
BundleName + "_" + localeLanguage
BundleName
Observe that the property file serving as the bundle for France (shown in Listing 2) was named Message_fr_FR.properties . Bundles pertaining to a specific country need to have both the language code and country code appear within the prefix. (I could also have used the optional application-specific variant and further specialized the file as Message_fr_FR_MAC.properties -- the bundle for all French-speaking Mac users from France. But I shall resist the temptation!) Similarly, the bundle containing the German labels is named Message_de_DE.properties , and so on. Resources contains links for obtaining valid country and language codes. For the overly curious, the following code shows the source you can use to create a classfile, serving the same purpose as the property file shown in Listing 2:
public class Message_fr_FR extends ListResourceBundle {
public Object[][] getContents() {
return contents;
}
static final Object[][] contents = {
{"main.title", "Musique sans frontières"},
{"main.subhead", "Sons du village global"},
{"main.addLabel","Ajouter"},
. . .
{"cd.quantityLabel","Quantité"}
}
}
You might wonder why the property file containing the English labels (shown in Listing 1) does not contain a country or language code in its prefix. Although I could have named the bundle Message_en_US.properties , I chose to simply call it Message.properties . Any bundle that contains neither country nor language code is treated as the default bundle and serves a specific purpose: it is picked up as a last resort if there is no other matching bundle for the requested locale. Observe that the literals used to identify resources remain the same within the bundles for all locales; only the values change for the corresponding locale. Now that I have isolated the GUI elements and localized them within the property files, I'll show how you can use them within a JSP page.
Listing 1: Message.properties
main.title=Music Without Borders
main.subhead=Sounds from the Global Village
main.addLabel=Add
main.qtyLabel=Quantity
main.bgcolor=#33CCFF
cart.bgcolor=#FFFFFF
cart.delLabel=Delete
cart.checkoutLabel=Checkout
checkout.bgcolor=#33CCFF
checkout.title=Music Without Borders Checkout
checkout.subhead=Thanks for your order!
checkout.totalLabel=Total
checkout.returnLabel=Shop some more!
dollar.exchRate=1.00
cd.albumLabel=Album
cd.artistLabel=Artist
cd.countryLabel=Country
cd.priceLabel=Price
cd.quantityLabel=Quantity
Listing 2: Message_fr_FR.properties
main.title=Musique sans frontières
main.subhead=Sons du village global
main.addLabel=Ajouter
main.qtyLabel=Quantité
main.bgcolor=#33CCFF
cart.bgcolor=#FFFFFF
cart.delLabel=Supprimer
cart.checkoutLabel=Passez à la caisse
checkout.bgcolor=#33CCFF
checkout.title= Caisse pour Musique sans frontières
checkout.subhead=Merci pour votre commande!
checkout.totalLabel=Total
checkout.returnLabel=Faites d'autres commandes!
dollar.exchRate=6.48
cd.albumLabel=Album
cd.artistLabel=Artiste
cd.countryLabel=Pays
cd.priceLabel=Prix
cd.quantityLabel=Quantité
The JSP page i18nDemo.jsp (shown in Listing 3) acts as the gateway to the online store. Its main task is to enable the user to select an appropriate language for viewing the site, as shown in Figure 1.
Figure 1. Gateway to the internationalized Web application
In Java, the focal point of all internationalization activity is the java.util.Locale class, which serves to encapsulate the country code, language code, and the optional variant code. The Locale class also provides a number of convenient constants representing the most commonly used locales. Consider the following snippet, which establishes the locale for the Web application:
Locale locale=null;
if (lang.equals("German")) {
locale=Locale.GERMANY;
} else if (lang.equals("French")) {
locale=Locale.FRANCE;
} else if (lang.equals("Swedish")) {
locale=new Locale("sv","SE");
} else {
locale=Locale.US;
}
While the Locale instance is typically obtained from a predefined constant within the Locale class, it can also be instantiated using the class's constructor. You can do this by specifying the language code and country code (there is also another version of the Locale constructor that additionally accepts an application-specific variant code). The language code is two lowercase letters, and the country code is always two uppercase letters. (As mentioned earlier, you can find a link to lists of valid country and language code in Resources .)
Since I do not have a predefined constant for Sweden, observe that its Locale instance is instantiated by explicitly passing the language and country code as:
locale=new Locale("sv","SE");
Once the locale has been established, you can retrieve its corresponding bundle:
ResourceBundle bundle =
ResourceBundle.getBundle("Message", locale);
You can store the bundles anywhere in the classpath, as understood by your application server or J
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