Java localization demo. Demonstrates: * localizing by putting values to files * Using more general description when specific is not available * Winning of more specific locale description * Getting resource bundles outside classpath * Changing resource bundles on runtime No third party dependencies, just core java. Written just for demo purpose…

Runner.java

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.Locale;
import java.util.ResourceBundle;

/**
 * Java localization demo.
 */
public class Runner {
    /**
     * Run for demo.
     */
    public static void main(String[] args) {
        fillData();  //prepare files
        demoRead();  //read with different locales
        writeDemo(); //check changing property files
    }
    
    /**
     * Fills files with some fake data.
     */
    private static void fillData() {
        //    file                  values          keys
        fill("r",               "default",      "foo1", "foo3");
        fill("r_en",            "en",           "foo2", "foo3");
        fill("r_en_US",         "en_US",        "foo3", "foo4");
        fill("r_en_US_ABCLTD",  "en_US_ABCLTD", "foo3", "foo4");
        fill("r_en__ABCLTD",    "en__ABCLTD",   "foo5");
    }

    /**
     * Showing basics of reading values from bundles.
     */
    private static void demoRead() {
        //Using default: presented in r, r_en. Fr locale. r wins
        print(loadBundle(new Locale("fr")).getString("foo1")); //=>default

        //More specific wins: presented in r_en. en_US locale. r_en_US wins
        print(loadBundle(new Locale("en", "US")).getString("foo2")); //=>en

        //More specific wins(variant example): presented in r, r_en, en_US_ABCLTD. en_US_ABCLTD locale. r_en_US_ABCLTD wins
        print(loadBundle(new Locale("en", "US", "ABCLTD")).getString("foo3")); //=>en_US_ABCLTD

        //Using less specific: presented in r_en_US. en_US_ABCLTD locale. r_en wins
        print(loadBundle(new Locale("en", "US", "ABCLTD")).getString("foo4")); //=>en_US


        //Using variant without country: presented in r_en__ABCLTD. en__ABCLTD locale. r_en__ABCLTD wins
        print(loadBundle(new Locale("en", "", "ABCLTD")).getString("foo5")); //=>en__ABCLTD
        
        //Doesn't work. Could not use r_en__ABCLTD for en_US_ABCLTD locale
        //print(loadBundle(new Locale("en", "US", "ABCLTD")).getString("foo5")); //=>en__ABCLTD
    }

    /**
     * Showing changing properties during runtime.
     */
    private static void writeDemo() {
        fill("r", "default", "foo1", "foo3");
        print(loadBundle(new Locale("fr")).getString("foo1")); //=>default
        fill("r", "overriden", "foo1", "foo3");
        print(loadBundle(new Locale("fr")).getString("foo1")); //=>overriden
    }

    /**
     * Getting resource bundles from file system (outside jar/classpath).
     */
    private static ResourceBundle loadBundle(Locale locale) {
        try {
            File file = new File(RESOURCES_LOCATION);
            URL[] urls = {file.toURI().toURL()};
            ClassLoader loader = new URLClassLoader(urls);

            return ResourceBundle.getBundle(RESOURCE_NAME, locale, loader);
        } catch (MalformedURLException e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * Fills property file with name fileName with properties from keys with same value.
     * (Very dummy impl)
     *
     * @param fileName property file
     * @param value    value for properties
     * @param keys     properties
     */
    private static void fill(String fileName, String value, String... keys) {
        try {

            new File(RESOURCES_LOCATION).mkdirs();
            final File file = new File(RESOURCES_LOCATION, fileName + ".properties");
            file.delete();
            file.createNewFile();

            final PrintWriter writer = new PrintWriter(file);
            for (String each : keys) {
                writer.println(String.format("%s=%s", each, value));
            }
            writer.flush();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * Just helper method.
     */
    private static void print(String val) {
        System.out.println(val);
    }
    
    /**
     * Basic resource name.
     */
    private static final String RESOURCE_NAME = "r";
    /**
     * Work directory. Should be cleaned after experimenting.
     */
    private static final String RESOURCES_LOCATION = "D:\\localization";
}