src/java/org/apache/xmlgraphics/util/i18n/LocalizableSupport.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */

/* $Id$ */

package org.apache.xmlgraphics.util.i18n;

import java.text.MessageFormat;
import java.util.Locale;
import java.util.ResourceBundle;

// CSOFF: InnerAssignment

/**
 * This class provides a default implementation of the Localizable interface.
 * You can use it as a base class or as a member field and delegates various
 * work to it.<p>
 * For example, to implement Localizable, the following code can be used:
 * <pre>
 *  package mypackage;
 *  ...
 *  public class MyClass implements Localizable {
 *      // This code fragment requires a file named
 *      // 'mypackage/resources/Messages.properties', or a
 *      // 'mypackage.resources.Messages' class which extends
 *      // java.util.ResourceBundle, accessible using the current
 *      // classpath.
 *      LocalizableSupport localizableSupport =
 *          new LocalizableSupport("mypackage.resources.Messages");
 *
 *      public void setLocale(Locale l) {
 *          localizableSupport.setLocale(l);
 *      }
 *      public Local getLocale() {
 *          return localizableSupport.getLocale();
 *      }
 *      public String formatMessage(String key, Object[] args) {
 *          return localizableSupport.formatMessage(key, args);
 *      }
 *  }
 * </pre>
 * The algorithm for the Locale lookup in a LocalizableSupport object is:
 * <ul>
 *   <li>
 *     if a Locale has been set by a call to setLocale(), use this Locale,
 *     else,
 *   </li>
 *   <li>
 *     if a Locale has been set by a call to the setDefaultLocale() method
 *     of a LocalizableSupport object in the current LocaleGroup, use this
 *     Locale, else,
 *   </li>
 *   <li>
 *     use the object returned by Locale.getDefault() (and set by
 *     Locale.setDefault()).
 *   </li>
 * </ul>
 * This offers the possibility to have a different Locale for each object,
 * a Locale for a group of object and/or a Locale for the JVM instance.
 * <p>
 * Note: if no group is specified a LocalizableSupport object belongs to a
 * default group common to each instance of LocalizableSupport.
 *
 * @version $Id$
 *
 * Originally authored by Stephane Hillion.
 */
public class LocalizableSupport implements Localizable {
    /**
     * The locale group to which this object belongs.
     */
    protected LocaleGroup localeGroup = LocaleGroup.DEFAULT;

    /**
     * The resource bundle classname.
     */
    protected String bundleName;

    /**
     * The classloader to use to create the resource bundle.
     */
    protected ClassLoader classLoader;

    /**
     * The current locale.
     */
    protected Locale locale;

    /**
     * The locale in use.
     */
    protected Locale usedLocale;

    /**
     * The resources
     */
    protected ResourceBundle resourceBundle;

    /**
     * Same as LocalizableSupport(s, null).
     */
    public LocalizableSupport(String s) {
        this(s, null);
    }

    /**
     * Creates a new Localizable object.
     * The resource bundle class name is required allows the use of custom
     * classes of resource bundles.
     * @param s  must be the name of the class to use to get the appropriate
     *           resource bundle given the current locale.
     * @param cl is the classloader used to create the resource bundle,
     *           or null.
     * @see java.util.ResourceBundle
     */
    public LocalizableSupport(String s, ClassLoader cl) {
        bundleName = s;
        classLoader = cl;
    }

    /**
     * Implements {@link org.apache.xmlgraphics.util.i18n.Localizable#setLocale(Locale)}.
     */
    public void setLocale(Locale l) {
        if (locale != l) {
            locale = l;
            resourceBundle = null;
        }
    }

    /**
     * Implements {@link org.apache.xmlgraphics.util.i18n.Localizable#getLocale()}.
     */
    public Locale getLocale() {
        return locale;
    }

    /**
     * Implements {@link
     * org.apache.xmlgraphics.util.i18n.ExtendedLocalizable#setLocaleGroup(LocaleGroup)}.
     */
    public void setLocaleGroup(LocaleGroup lg) {
        localeGroup = lg;
    }

    /**
     * Implements {@link
     * org.apache.xmlgraphics.util.i18n.ExtendedLocalizable#getLocaleGroup()}.
     */
    public LocaleGroup getLocaleGroup() {
        return localeGroup;
    }

    /**
     * Implements {@link
     * org.apache.xmlgraphics.util.i18n.ExtendedLocalizable#setDefaultLocale(Locale)}.
     * Later invocations of the instance methods will lead to update the
     * resource bundle used.
     */
    public void setDefaultLocale(Locale l) {
        localeGroup.setLocale(l);
    }

    /**
     * Implements {@link
     * org.apache.xmlgraphics.util.i18n.ExtendedLocalizable#getDefaultLocale()}.
     */
    public Locale getDefaultLocale() {
        return localeGroup.getLocale();
    }

    /**
     * Implements {@link
     * org.apache.xmlgraphics.util.i18n.Localizable#formatMessage(String,Object[])}.
     */
    public String formatMessage(String key, Object[] args) {
        getResourceBundle();
        return MessageFormat.format(resourceBundle.getString(key), args);
    }

    /**
     * Implements {@link
     * org.apache.xmlgraphics.util.i18n.ExtendedLocalizable#getResourceBundle()}.
     */
    public ResourceBundle getResourceBundle() {
        Locale l;

        if (resourceBundle == null) {
            if (locale == null) {
                if ((l = localeGroup.getLocale()) == null) {
                    usedLocale = Locale.getDefault();
                } else {
                    usedLocale = l;
                }
            } else {
                usedLocale = locale;
            }
            if (classLoader == null) {
                resourceBundle = ResourceBundle.getBundle(bundleName,
                                                          usedLocale);
            } else {
                resourceBundle = ResourceBundle.getBundle(bundleName,
                                                          usedLocale,
                                                          classLoader);
            }
        } else if (locale == null) {
            // Check for group Locale and JVM default locale changes.
            if ((l = localeGroup.getLocale()) == null) {
                if (usedLocale != (l = Locale.getDefault())) {
                    usedLocale = l;
                    if (classLoader == null) {
                        resourceBundle = ResourceBundle.getBundle(bundleName,
                                                                  usedLocale);
                    } else {
                        resourceBundle = ResourceBundle.getBundle(bundleName,
                                                                  usedLocale,
                                                                  classLoader);
                    }
                }
            } else if (usedLocale != l) {
                usedLocale = l;
                if (classLoader == null) {
                    resourceBundle = ResourceBundle.getBundle(bundleName,
                                                              usedLocale);
                } else {
                    resourceBundle = ResourceBundle.getBundle(bundleName,
                                                              usedLocale,
                                                              classLoader);
                }
            }
        }

        return resourceBundle;
    }
}