LocaleInitializer.java

package org.utplsql.cli;

import java.util.Locale;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/** This class makes sure the java locale is set according to the environment variables LC_ALL and LANG
 * We experienced that, in some cases, the locale was not set as expected, therefore this class implements some clear
 * rules:
 *   1. If environment variable NLS_LANG is set, we try to parse its content and set locale according to its value if valid
 *   2. If environment variable LC_ALL is set, we try to parse its content and set locale according to its value if valid
 *   3. If environment variable LANG is set, we try to parse its content and set locale according to its value if valid
 *   4. Otherwise we use default locale
 *
 *   @author pesse
 */
class LocaleInitializer {

    private static final Pattern REGEX_LOCALE = Pattern.compile("^([a-zA-Z]+)[_-]([a-zA-Z]+)"); // We only need the very first part and are pretty forgiving in parsing

    /** Sets the default locale according to the rules described above
     *
     */
    static void initLocale() {

        boolean localeChanged = setDefaultLocale(System.getenv("NLS_LANG"));

        if ( !localeChanged )
            localeChanged = setDefaultLocale(System.getenv("LC_ALL"));
        if ( !localeChanged )
            setDefaultLocale(System.getenv("LANG"));
    }

    /** Set the default locale from a given string like LC_ALL or LANG environment variable
     *
     * @param localeString Locale-string from LC_ALL or LANG, e.g "en_US.utf-8"
     * @return true if successful, false if not
     */
    private static boolean setDefaultLocale( String localeString ) {
        if ( localeString == null || localeString.isEmpty() )
            return false;

        try {
            Matcher m = REGEX_LOCALE.matcher(localeString);
            if (m.find()) {
                StringBuilder sb = new StringBuilder();
                sb.append(m.group(1));
                if (m.group(2) != null)
                    sb.append("-").append(m.group(2));

                Locale l = new Locale.Builder().setLanguageTag(sb.toString()).build();
                if ( l != null ) {
                    Locale.setDefault(l);
                    return true;
                }
            }
        }
        catch ( Exception e ) {
            System.out.println("Could not get locale from " + localeString);
        }

        return false;
    }
}