ClasspathLocalizationRepository.java

/*
 * Chrysalix
 * See the COPYRIGHT.txt file distributed with this work for information
 * regarding copyright ownership.  Some portions may be licensed
 * to Red Hat, Inc. under one or more contributor license agreements.
 * See the AUTHORS.txt file in the distribution for a full listing of 
 * individual contributors.
 *
 * Chrysalix is free software. Unless otherwise indicated, all code in Chrysalix
 * is licensed to you under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * Chrysalix is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.chrysalix.common.i18n;

import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;

import org.chrysalix.common.CheckArg;
import org.chrysalix.common.I18n;

/**
 * Class that loads a properties file from the classpath of the supplied {@link ClassLoader class loader}.
 * <p>
 * This repository for a property file by building locations of the form "path/to/class_locale.properties", where "path/to/class" is
 * created from the fully-qualified classname and all "." replaced with "/" characters, "locale" is the a variant of the locale
 * (first the full locale, then subsequently with the last segment removed). As soon as a property file is found, its URL is
 * returned immediately.
 * </p>
 * named with a name that matches
 */
public final class ClasspathLocalizationRepository {

    /**
     * Obtain the URL to the properties file containing the localized messages given the supplied bundle name. This method is
     * responsible for searching to find the most appropriate localized messages given the locale, but does not need to search using
     * the {@link Locale#getDefault() default locale} (as that is done by the {@link I18n#text(Object...) calling} method.
     * 
     * @param classLoader
     *        the classloader that should be used to load the localization bundles
     * @param bundleName
     *        the name of the bundle of properties; never null
     * @param locale
     *        the locale for which the properties file URL is desired
     * @return the URL to the properties file containing the localized messages for the named bundle, or null if no such bundle
     *         could be found
     */
    public static URL getLocalizationBundle( final ClassLoader classLoader,
                                             final String bundleName,
                                             final Locale locale ) {
        CheckArg.notNull( classLoader, "classLoader" );
        URL url = null;
        final List< String > paths = getPathsToSearchForBundle( bundleName, locale );
        for ( final String path : paths ) {
            url = classLoader.getResource( path );
            if ( url != null ) {
                return url;
            }
        }
        return url;
    }

    /**
     * Returns a list of paths (as string) of the different bundles searched in the
     * {@link ClasspathLocalizationRepository#getLocalizationBundle(ClassLoader, String, java.util.Locale)} method.
     * 
     * @param bundleName
     *        the name of the bundle of properties; never null
     * @param locale
     *        the locale for which the properties file URL is desired
     * @return a list of paths which the repository would look at.
     */
    public static List< String > getPathsToSearchForBundle( final String bundleName,
                                                            final Locale locale ) {
        final List< String > result = new ArrayList<>();
        final String pathPrefix = bundleName.replaceAll( "\\.", "/" );
        String localeVariant = '_' + locale.toString();
        int ndx = localeVariant.lastIndexOf( '_' );

        while ( ndx >= 0 ) {
            final String path = pathPrefix + localeVariant + ".properties";
            result.add( path );
            localeVariant = localeVariant.substring( 0, ndx );
            ndx = localeVariant.lastIndexOf( '_' );
        }
        result.add( pathPrefix + localeVariant + ".properties" );
        return result;
    }

    private ClasspathLocalizationRepository() {}
}