Earlier in this lesson you have learned how to create and access objects of the
ResourceBundle
class. This section extents your knowledge and explains how to take an advantage from theResourceBundel.Control
class capabilities.The
ResourceBundle.Control
was created to specify how to locate and instantiate resource bundles. It defines a set of callback methods that are invoked by theResourceBundle.getBundle
factory methods during the bundle loading process.Unlike a
ResourceBundle.getBundle
method described earlier, thisResourceBundle.getBundle
method defines a resource bundle using the specified base name, the default locale and the specified control.public static final ResourceBundle getBundle(String baseName, ResourceBundle.Control cont ...The specified control provide information for the resource bundle loading process.
The following sample program called
RBControl.java
illustrates how to define your own search paths for Chinese locales.1. Create the
properties
Files.As it was described before you can load your resources either from classes or from
properties
files. These files contain descriptions for the following locales:
– Global
RBControl.properties
– Language only: Simplified Chineese
RBControl_zh.properties
– Region only: China
RBControl_zh_cn.properties
– Region only: Hong Kong
RBControl_zh_hk.properties
– Taiwan
RBControl_zh_tw.properties
In this example an application creates a new locale for the Hong Kong region.
2. Create a
ResourceBundle
instance.As in the example in the previous section, this application creates a
ResourceBundle
instance by invoking thegetBundle
method:private static void test(Locale locale) { ResourceBundle rb = ResourceBundle.getBundle("RBControl", locale, new ResourceBundle.Control() { ...The
getBundle
method searches forproperties
files with the RBControl prefix. However, this method contains aControl
parameter, which drives the process of searching the Chineese locales.3. Invoke the
getCandidateLocales
methodThe
getCandidateLocales
method returns a list of theLocales
objects as candidate locales for the base name and locale.new ResourceBundle.Control() { @Override public List<Locale&rt; getCandidateLocales(String baseName, Locale locale) { ...The default implementation returns a list of the
Locale
objects as follows: Locale(language, country).However, this method is overriden to implement the following specific behavior:
{ if (baseName == null) throw new NullPointerException(); if (locale.equals(new Locale("zh", "HK"))) { return Arrays.asList( locale, Locale.TAIWAN, // no Locale.CHINESE here Locale.ROOT); } else if (locale.equals(Locale.TAIWAN)) { return Arrays.asList( locale, // no Locale.CHINESE here Locale.ROOT); }Note, that the last element of the sequence of candidate locales must be a root locale.4. Call the
test
classCall the
test
class for the following four different locales:public static void main(String[] args) { test(Locale.CHINA); test(new Locale("zh", "HK")); test(Locale.TAIWAN); test(Locale.CANADA); }5. Run the Sample Program
You will see the program output as follows:locale: zh_CN region: China language: Simplified Chinese locale: zh_HK region: Hong Kong language: Traditional Chinese locale: zh_TW region: Taiwan language: Traditional Chinese locale: en_CA region: global language: EnglishNote that the newly created was assigned the Hong Kong region, because it was specified in an appropriate
properties
file. Traditional Chinese was assigned as the language for the Taiwan locale.Two other interesting methods of the
ResourceBundle.Control
class were not used in theRBControl
example, but they deserved to be mentioned. ThegetTimeToLive
method is used to determine how long the resource bundle can exist in the cache. If the time limit for a resource bundle in the cache has expired, theneedsReload
method is invoked to determine whether the resource bundle needs to be reloaded.