Chapter 4
Isolating Locale-Specific Data with Resource Bundles
Error messages, status messages, graphic images, and even sound clips are
perfect examples of candidate elements for localization. For instance, all
text messages displayed to users throughout your program first need to be
translated, or localized, for the locales that you're going to support.
This task can be very time consuming and costly. After completing the
task, how do you package these messages together so the proper locale-
specific information gets displayed to the user?
Java's ResourceBundle class provides the functionality for you
to retrieve locale-specific resources. You can use resource bundles in your
application to keep text messages, formatting conventions, images, sound
files, etc., in a "package" targeted to different locales. It is possible
to use the ResourceBundle class by providing your own subclass;
however, two concrete implementations of ResourceBundle exist:
PropertyResourceBundle and ListResourceBundle.
These two classes provide additional functionality over the base
ResourceBundle class.
Why Use Resource Bundles?
Applications need to provide locale-sensitive information to users. One
approach is to hardcode locale-sensitive information or messages within the
application. However, this approach is inefficient because it makes your
application larger, complicates your application logic when you decide
which messages to display, and requires that you change or release a new
version of your application when locale-specific resources change. Another
approach, Java resource bundles, provides facilities for packaging and
managing collections of locale-specific elements, such as feedback or
status messages. These elements may also be more complex datatypes, such as
graphic images or sound files. The resource bundle facilities provide a
convenient mechanism for you to separate your program code from your
resource data.
Let's outline some general resource bundle properties. These properties are
illustrated in Figure 4-1. Resource bundles:
- Provide facilities for storage and retrieval of all locale-specific information.
- Allow you to support multiple locales in a single application.
- Allow you to support additional locales easily in the future by simply adding more resource bundles.
Figure 4-1. How resource bundles fit into application development
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