resourcebundle.java

gcc的组建

  /**
   * Get the appropriate ResourceBundle for the given locale. The following
   * strategy is used:
   *
   * <p>A sequence of candidate bundle names are generated, and tested in
   * this order, where the suffix 1 means the string from the specified
   * locale, and the suffix 2 means the string from the default locale:</p>
   *
   * <ul>
   * <li>baseName + "_" + language1 + "_" + country1 + "_" + variant1</li>
   * <li>baseName + "_" + language1 + "_" + country1</li>
   * <li>baseName + "_" + language1</li>
   * <li>baseName + "_" + language2 + "_" + country2 + "_" + variant2</li>
   * <li>baseName + "_" + language2 + "_" + country2</li>
   * <li>baseName + "_" + language2</li>
   * <li>baseName</li>
   * </ul>
   *
   * <p>In the sequence, entries with an empty string are ignored. Next,
   * <code>getBundle</code> tries to instantiate the resource bundle:</p>
   *
   * <ul>
   * <li>First, an attempt is made to load a class in the specified classloader
   * which is a subclass of ResourceBundle, and which has a public constructor
   * with no arguments, via reflection.</li>
   * <li>Next, a search is made for a property resource file, by replacing
   * '.' with '/' and appending ".properties", and using
   * ClassLoader.getResource(). If a file is found, then a
   * PropertyResourceBundle is created from the file's contents.</li>
   * </ul>
   * If no resource bundle was found, a MissingResourceException is thrown.
   *
   * <p>Next, the parent chain is implemented. The remaining candidate names
   * in the above sequence are tested in a similar manner, and if any results
   * in a resource bundle, it is assigned as the parent of the first bundle
   * using the <code>setParent</code> method (unless the first bundle already
   * has a parent).</p>
   *
   * <p>For example, suppose the following class and property files are
   * provided: MyResources.class, MyResources_fr_CH.properties,
   * MyResources_fr_CH.class, MyResources_fr.properties,
   * MyResources_en.properties, and MyResources_es_ES.class. The contents of
   * all files are valid (that is, public non-abstract subclasses of
   * ResourceBundle with public nullary constructors for the ".class" files,
   * syntactically correct ".properties" files). The default locale is
   * Locale("en", "UK").</p>
   *
   * <p>Calling getBundle with the shown locale argument values instantiates
   * resource bundles from the following sources:</p>
   *
   * <ul>
   * <li>Locale("fr", "CH"): result MyResources_fr_CH.class, parent
   *   MyResources_fr.properties, parent MyResources.class</li>
   * <li>Locale("fr", "FR"): result MyResources_fr.properties, parent
   *   MyResources.class</li>
   * <li>Locale("de", "DE"): result MyResources_en.properties, parent
   *   MyResources.class</li>
   * <li>Locale("en", "US"): result MyResources_en.properties, parent
   *   MyResources.class</li>
   * <li>Locale("es", "ES"): result MyResources_es_ES.class, parent
   *   MyResources.class</li>
   * </ul>
   * 
   * <p>The file MyResources_fr_CH.properties is never used because it is hidden
   * by MyResources_fr_CH.class.</p>
   *
   * @param baseName the name of the ResourceBundle
   * @param locale A locale
   * @param classLoader a ClassLoader
   * @return the desired resource bundle
   * @throws MissingResourceException if the resource bundle can't be found
   * @throws NullPointerException if any argument is null
   * @since 1.2
   */
  // This method is synchronized so that the cache is properly
  // handled.
  public static synchronized ResourceBundle getBundle
    (String baseName, Locale locale, ClassLoader classLoader)
  {
    // If the default locale changed since the last time we were called,
    // all cache entries are invalidated.
    Locale defaultLocale = Locale.getDefault();
    if (defaultLocale != lastDefaultLocale)
      {
	bundleCache = new HashMap();
	lastDefaultLocale = defaultLocale;
      }

    // This will throw NullPointerException if any arguments are null.
    lookupKey.set(baseName, locale, classLoader);
    
    Object obj = bundleCache.get(lookupKey);
    ResourceBundle rb = null;
    
    if (obj instanceof ResourceBundle)
      {
        return (ResourceBundle) obj;
      }
    else if (obj == nullEntry)
      {
        // Lookup has failed previously. Fall through.
      }
    else
      {
	// First, look for a bundle for the specified locale. We don't want
	// the base bundle this time.
	boolean wantBase = locale.equals(defaultLocale);
	ResourceBundle bundle = tryBundle(baseName, locale, classLoader, 
					  wantBase);

        // Try the default locale if neccessary.
	if (bundle == null && !locale.equals(defaultLocale))
	  bundle = tryBundle(baseName, defaultLocale, classLoader, true);

	BundleKey key = new BundleKey(baseName, locale, classLoader);
        if (bundle == null)
	  {
	    // Cache the fact that this lookup has previously failed.
	    bundleCache.put(key, nullEntry);
	  }
	else
	  {
            // Cache the result and return it.
	    bundleCache.put(key, bundle);
	    return bundle;
	  }
      }

    throw new MissingResourceException("Bundle " + baseName 
				       + " not found for locale "
				       + locale
				       + " by classloader "
				       + classLoader,
				       baseName, "");
  }

  /**
   * Override this method to provide the resource for a keys. This gets
   * called by <code>getObject</code>. If you don't have a resource
   * for the given key, you should return null instead throwing a
   * MissingResourceException. You don't have to ask the parent, getObject()
   * already does this; nor should you throw a MissingResourceException.
   *
   * @param key the key of the resource
   * @return the resource for the key, or null if not in bundle
   * @throws NullPointerException if key is null
   */
  protected abstract Object handleGetObject(String key);

  /**
   * This method should return all keys for which a resource exists; you
   * should include the enumeration of any parent's keys, after filtering out
   * duplicates.
   *
   * @return an enumeration of the keys
   */
  public abstract Enumeration getKeys();

  /**
   * Tries to load a class or a property file with the specified name.
   *
   * @param localizedName the name
   * @param classloader the classloader
   * @return the resource bundle if it was loaded, otherwise the backup
   */
  private static ResourceBundle tryBundle(String localizedName,
                                          ClassLoader classloader)
  {
    ResourceBundle bundle = null;
    try
      {
        Class rbClass;
        if (classloader == null)
          rbClass = Class.forName(localizedName);
        else
          rbClass = classloader.loadClass(localizedName);
	// Note that we do the check up front instead of catching
	// ClassCastException.  The reason for this is that some crazy
	// programs (Eclipse) have classes that do not extend
	// ResourceBundle but that have the same name as a property
	// bundle; in fact Eclipse relies on ResourceBundle not
	// instantiating these classes.
	if (ResourceBundle.class.isAssignableFrom(rbClass))
	  bundle = (ResourceBundle) rbClass.newInstance();
      }
    catch (IllegalAccessException ex) {}
    catch (InstantiationException ex) {}
    catch (ClassNotFoundException ex) {}

    if (bundle == null)
      {
	try
	  {
	    InputStream is;
	    String resourceName
	      = localizedName.replace('.', '/') + ".properties";
	    if (classloader == null)
	      is = ClassLoader.getSystemResourceAsStream(resourceName);
	    else
	      is = classloader.getResourceAsStream(resourceName);
	    if (is != null)
	      bundle = new PropertyResourceBundle(is);
	  }
	catch (IOException ex)
	  {
	    MissingResourceException mre = new MissingResourceException
	      ("Failed to load bundle: " + localizedName, localizedName, "");
	    mre.initCause(ex);
	    throw mre;
	  }
      }

    return bundle;
  }

  /**
   * Tries to load a the bundle for a given locale, also loads the backup
   * locales with the same language.
   *
   * @param baseName the raw bundle name, without locale qualifiers
   * @param locale the locale
   * @param classLoader the classloader
   * @param wantBase whether a resource bundle made only from the base name
   *        (with no locale information attached) should be returned.
   * @return the resource bundle if it was loaded, otherwise the backup
   */
  private static ResourceBundle tryBundle(String baseName, Locale locale,
                                          ClassLoader classLoader, 
					  boolean wantBase)
  {
    String language = locale.getLanguage();
    String country = locale.getCountry();
    String variant = locale.getVariant();
    
    int baseLen = baseName.length();

    // Build up a StringBuffer containing the complete bundle name, fully
    // qualified by locale.
    StringBuffer sb = new StringBuffer(baseLen + variant.length() + 7);

    sb.append(baseName);
    
    if (language.length() > 0)
      {
	sb.append('_');
	sb.append(language);
	
	if (country.length() > 0)
	  {
	    sb.append('_');
	    sb.append(country);
	    
	    if (variant.length() > 0)
	      {
	        sb.append('_');
		sb.append(variant);
	      }
	  }
      }

    // Now try to load bundles, starting with the most specialized name.
    // Build up the parent chain as we go.
    String bundleName = sb.toString();
    ResourceBundle first = null; // The most specialized bundle.
    ResourceBundle last = null; // The least specialized bundle.
    
    while (true)
      {
        ResourceBundle foundBundle = tryBundle(bundleName, classLoader);
	if (foundBundle != null)
	  {
	    if (first == null)
	      first = foundBundle;
	    if (last != null)
	      last.parent = foundBundle;
	    foundBundle.locale = locale;
	    last = foundBundle;
	  }
	int idx = bundleName.lastIndexOf('_');
	// Try the non-localized base name only if we already have a
	// localized child bundle, or wantBase is true.
	if (idx > baseLen || (idx == baseLen && (first != null || wantBase)))
	  bundleName = bundleName.substring(0, idx);
	else
	  break;
      }
    
    return first;
  }
}