i18n.java

一个论坛程序的简单实现

/*
 * Copyright (c) 2003, 2004 Rafael Steil
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, 
 * with or without modification, are permitted provided 
 * that the following conditions are met:
 * 
 * 1) Redistributions of source code must retain the above 
 * copyright notice, this list of conditions and the 
 * following  disclaimer.
 * 2)  Redistributions in binary form must reproduce the 
 * above copyright notice, this list of conditions and 
 * the following disclaimer in the documentation and/or 
 * other materials provided with the distribution.
 * 3) Neither the name of "Rafael Steil" nor 
 * the names of its contributors may be used to endorse 
 * or promote products derived from this software without 
 * specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT 
 * HOLDERS AND CONTRIBUTORS "AS IS" AND ANY 
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, 
 * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR 
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL 
 * THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE 
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES 
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, 
 * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER 
 * IN CONTRACT, STRICT LIABILITY, OR TORT 
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE
 * 
 * This file creation date: Mar 10, 2003 / 9:28:40 PM
 * The JForum Project
 * http://www.jforum.net
 */
package net.jforum.util;

import java.io.FileInputStream;
import java.io.IOException;
import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Properties;

import org.apache.log4j.Logger;

import net.jforum.SessionFacade;
import net.jforum.entities.UserSession;
import net.jforum.util.preferences.ConfigKeys;
import net.jforum.util.preferences.SystemGlobals;

/**
 * I18n (Internationalization) class implementation. Does nothing of special, just loads the
 * messages into memory and provides a static method to acess them.
 * 
 * @author Rafael Steil
 * @author James Yong
 * @version $Id: I18n.java,v 1.20 2004/10/25 20:52:09 rafaelsteil Exp $
 */
public class I18n {
    private static I18n classInstance = new I18n();

    private static HashMap messagesMap = new HashMap();

    private static Properties localeNames = new Properties();

    private static String defaultName;

    private static String baseDir;

    private static List watching = new ArrayList();

    public static final String CANNOT_DELETE_GROUP = "CannotDeleteGroup";

    public static final String CANNOT_DELETE_CATEGORY = "CannotDeleteCategory";

    private static final Logger logger = Logger.getLogger(I18n.class);

    private I18n() {
    }

    /**
     * Gets the singleton
     * 
     * @return Instance of I18n class
     */
    public static I18n getInstance() {
        return classInstance;
    }

    /**
     * Load the default I18n file
     * 
     * @throws IOException
     */
    public static synchronized void load() throws IOException {
        baseDir = SystemGlobals.getApplicationResourceDir() + "/"
                + SystemGlobals.getValue(ConfigKeys.LOCALES_DIR);

        loadLocales();

        defaultName = SystemGlobals.getValue(ConfigKeys.I18N_DEFAULT_ADMIN);
        load(defaultName, null);

        String custom = SystemGlobals.getValue(ConfigKeys.I18N_DEFAULT);
        if (!custom.equals(defaultName)) {
            load(custom, defaultName);
            defaultName = custom;
        }
    }

    private static void loadLocales() throws IOException {
        localeNames.load(new FileInputStream(baseDir
                + SystemGlobals.getValue(ConfigKeys.LOCALES_NAMES)));
    }

    static void load(String localeName, String mergeWith) throws IOException {
        if (localeNames.size() == 0) {
            loadLocales();
        }

        Properties p = new Properties();

        if (mergeWith != null) {
            if (!I18n.contains(mergeWith)) {
                load(mergeWith, null);
            }

            p.putAll((Properties) messagesMap.get(mergeWith));
        }

        p.load(new FileInputStream(baseDir + localeNames.getProperty(localeName)));
        messagesMap.put(localeName, p);

        watchForChanges(localeName);
    }

    public static void load(String localeName) throws IOException {
        load(localeName, SystemGlobals.getValue(ConfigKeys.I18N_DEFAULT));
    }

    public static void reset() {
        messagesMap = new HashMap();
        localeNames = new Properties();
        defaultName = null;
    }

    private static void watchForChanges(final String localeName) throws IOException {
        if (!watching.contains(localeName)) {
            watching.add(localeName);

            int fileChangesDelay = SystemGlobals.getIntValue(ConfigKeys.FILECHANGES_DELAY);

            if (fileChangesDelay > 0) {

                FileMonitor.getInstance().addFileChangeListener(new FileChangeListener() {
                    /**
                     * @see net.jforum.util.FileChangeListener#fileChanged(java.lang.String)
                     */
                    public void fileChanged(String filename) {
                        logger.info("Reloading i18n for " + localeName);

                        try {
                            I18n.load(localeName);
                        } catch (IOException e) {
                            logger.warn(e);
                            e.printStackTrace();
                        }
                    }
                }, baseDir + localeNames.getProperty(localeName), fileChangesDelay);
            }
        }
    }

    /**
     * Gets a I18N (internationalized) message.
     * 
     * @param localeName
     *            The locale name to retrieve the messages from
     * @param messageName
     *            The message name to retrieve. Must be a valid entry into the file specified by
     *            <code>i18n.file</code> property.
     * @param params
     *            Parameters needed by some messages. The messages with extra parameters are
     *            formated according to {@link java.text.MessageFormat}specification
     * @return String With the message
     */
    public static String getMessage(String localeName, String messageName, Object params[]) {
        return MessageFormat.format(((Properties) messagesMap.get(localeName))
                .getProperty(messageName), params);
    }

    /**
     * @see #getMessage(String, String, Object[])
     */
    public static String getMessage(String messageName, Object params[]) {
        String lang = "";
        UserSession us = SessionFacade.getUserSession();
        if (us != null && us.getLang() != null) {
            lang = us.getLang();
        }

        if ("".equals(lang)) {
            return getMessage(defaultName, messageName, params);
        } else {
            return getMessage(lang, messageName, params);
        }
    }

    /**
     * Gets an I18N (internationalization) message.
     * 
     * @param m
     *            The message name to retrieve. Must be a valid entry into the file specified by
     *            <code>i18n.file</code> property.
     * @return String With the message
     */
    public static String getMessage(String localeName, String m) {
        if (!messagesMap.containsKey(localeName)) {
            try {
                load(localeName);
            } catch (IOException e) {
                logger.warn("Error loading locale " + localeName + ". " + e.getMessage());
                return null;
            }
        }

        return (((Properties) messagesMap.get(localeName)).getProperty(m));
    }

    public static String getMessage(String m) {
        return getMessage(m, SessionFacade.getUserSession());
    }

    public static String getMessage(String m, UserSession us) {
        if (us == null || us.getLang() == null || us.getLang().equals("")) {
            return getMessage(defaultName, m);
        } else {
            return getMessage(us.getLang(), m);
        }
    }

    /**
     * Check whether the language is loaded in i18n.
     * 
     * @param language
     * @return boolean
     */
    public static boolean contains(String language) {
        return messagesMap.containsKey(language);
    }
    
    /**
     * Check if the given language exist.
     * 
     * @param language The language to check
     * @return <code>true</code> if the language is a valid and registered
     * translation.
     */
    public static boolean languageExists(String language) {
    	return (localeNames.getProperty(language) != null);
    }
}