Messages

/*
 * Copyright 2006 Assaf Arkin, Ralf Joachim
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 *
 * $Id: Messages.java 6907 2007-03-28 21:24:52Z rjoachim $
 */
package org.castor.core.util;

import java.text.MessageFormat;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Locale;
import java.util.MissingResourceException;
import java.util.ResourceBundle;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * I18N message formatting class. A static factory for obtaining messages and formatting messages
 * with arguments.
 * <p>
 * The resource file <tt>org.exolab.castor.util.resources.messages</tt> contains a list of all the
 * messages in English. Additional resource files can be added for other languages and locales by
 * placing them in the same package with a language/locale prefix. See the I18N documentation and
 * use of resource bundles in the JDK docs.
 *
 * @author <a href="mailto:arkin AT intalio DOT com">Assaf Arkin</a>
 * @author <a href="mailto:ralf DOT joachim AT syscon DOT eu">Ralf Joachim</a>
 * @version $Revision: 6907 $ $Date: 2006-04-10 16:39:24 -0600 (Mon, 10 Apr 2006) $
 * @since 1.0.1
 */
public final class Messages {
  // --------------------------------------------------------------------------

  /**
   * The <a href="http://jakarta.apache.org/commons/logging/">Jakarta Commons Logging </a> instance
   * used for all logging.
   */
  private static final Log LOG = LogFactory.getLog(Messages.class);

  /**
   * The name of the resource holding all the messages in the English language. Resources for other
   * languages and locales use the same name with a language/locale prefix.
   */
  public static final String RESOURCE_NAME = "org.castor.messages";

  /** The resource bundle holds all the messages. */
  private static ResourceBundle _messages;

  /** Once a format has been created once, it is cached here. */
  private static Hashtable<String, MessageFormat> _formats;
  // --------------------------------------------------------------------------

  static {
    setDefaultLocale();
  }

  // --------------------------------------------------------------------------

  /**
   * Set the default locale to use for loading messages. Calling this method will reload all the
   * messages based on the new locale name.
   */
  public static void setDefaultLocale() {
    setLocale(Locale.getDefault());
  }

  /**
   * Set the locale to use for loading messages. Calling this method will reload all the messages
   * based on the new locale name.
   *
   * @param locale the locale for which a resource bundle is desired.
   */
  public static void setLocale(final Locale locale) {
    try {
      _messages = ResourceBundle.getBundle(RESOURCE_NAME, locale);
    } catch (Exception except) {
      _messages = new EmptyResourceBundle();
      LOG.error("Failed to locate messages resource " + RESOURCE_NAME);
    }
    _formats = new Hashtable<>();
  }

  /**
   * Format the named message using a single argument and return the full message text.
   *
   * @param message The message name
   * @param arg1 The first argument
   * @return The full message text
   */
  public static String format(final String message, final Object arg1) {
    return format(message, new Object[] {arg1});
  }

  /**
   * Format the named message using two argument and return the full message text.
   *
   * @param message The message name
   * @param arg1 The first argument
   * @param arg2 The second argument
   * @return The full message text
   */
  public static String format(final String message, final Object arg1, final Object arg2) {
    return format(message, new Object[] {arg1, arg2});
  }

  /**
   * Format the named message using three argument and return the full message text.
   *
   * @param message The message name
   * @param arg1 The first argument
   * @param arg2 The second argument
   * @param arg3 The third argument
   * @return The full message text
   */
  public static String format(final String message, final Object arg1, final Object arg2,
      final Object arg3) {
    return format(message, new Object[] {arg1, arg2, arg3});
  }

  /**
   * Format the named message using any number of arguments and return the full message text.
   *
   * @param message The message name
   * @param args Argument list
   * @return The full message text
   */
  public static String format(final String message, final Object[] args) {

    try {
      MessageFormat mf = (MessageFormat) _formats.get(message);
      if (mf == null) {
        String msg;
        try {
          msg = _messages.getString(message);
        } catch (MissingResourceException except) {
          return message;
        }
        mf = new MessageFormat(msg);
        _formats.put(message, mf);
      }
      return mf.format(args);
    } catch (Exception except) {
      return "An internal error occured while processing message " + message;
    }
  }

  /**
   * Return the text of the named message without formatting.
   *
   * @param message The message name
   * @return The full message text
   */
  public static String message(final String message) {
    try {
      return _messages.getString(message);
    } catch (MissingResourceException except) {
      return message;
    }
  }

  // --------------------------------------------------------------------------

  /**
   * Hide default constructor of utility class.
   */
  private Messages() {}

  // --------------------------------------------------------------------------

  /**
   * A empty resource bundle.
   */
  private static class EmptyResourceBundle extends ResourceBundle implements Enumeration<String> {
    /**
     * {@inheritDoc}
     *
     * @see java.util.ResourceBundle#getKeys()
     */
    public Enumeration<String> getKeys() {
      return this;
    }

    /**
     * {@inheritDoc}
     *
     * @see java.util.ResourceBundle#handleGetObject(java.lang.String)
     */
    protected Object handleGetObject(final String name) {
      return "[Missing message " + name + "]";
    }

    /**
     * {@inheritDoc}
     *
     * @see java.util.Enumeration#hasMoreElements()
     */
    public boolean hasMoreElements() {
      return false;
    }

    /**
     * {@inheritDoc}
     *
     * @see java.util.Enumeration#nextElement()
     */
    public String nextElement() {
      return null;
    }
  }

  // --------------------------------------------------------------------------
}