libjava/java/util/PropertyResourceBundle.java

/* java.util.PropertyResourceBundle
   Copyright (C) 1998, 1999, 2001 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Classpath 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
General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.

As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module.  An independent module is a module which is not derived from
or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so.  If you do not wish to do so, delete this
exception statement from your version. */


package java.util;

import gnu.java.util.DoubleEnumeration;

/**
 * This class is a concrete <code>ResourceBundle</code> that gets it
 * resources from a property file.  This implies that the resources are
 * strings. For more information about resource bundles see the class
 * <code>ResourceBundle</code>.
 *
 * You should not use this class directly, or subclass it, but you get
 * an object of this class automatically when you call
 * <code>ResourceBundle.getBundle()</code> and there is a properties
 * file.
 *
 * If there is also a class for this resource and the same locale, the
 * class does win.
 *
 * The properties file should have the name of the resource bundle,
 * appended with the locale (e.g. <code>_de</code) and the extension
 * <code>.properties</code>.  The file should have the same format
 * as for <code>Properties.load()</code>
 *
 * XXX- move this to properties.
 * The file should have the following
 * format: An empty line or a line starting with <code>#</code> is
 * ignored.  An backslash (<code>\</code>) at the end of the line
 * makes the line continueing on the next line.  Otherwise, each line
 * describes a key/value pair.  The chars up to the first whitespace,
 * = or : are the key.  The key is followed by one or more
 * whitespaces, <code>=</code> or <code>:</code>.  The rest of the
 * line is the resource belonging to the key.  You can give unicode
 * characters with the <code>\\uxxxx</code> notation, where
 * <code>xxxx</code> is the hex encoding of the 16 bit unicode char
 * number.
 *
 * An example of a properties file for the german language is given
 * here.  This extends the example given in ListResourceBundle.
 * Create a file MyResource_de.properties with the following contents
 * and put it in the CLASSPATH.  (The char <code>\u00e4<char> is the 
 * german &auml;)
 * 
 * <pre>
 * s1=3
 * s2=MeineDisk
 * s3=3. M\u00e4rz 96
 * s4=Die Diskette ''{1}'' enth\u00e4lt {0} in {2}.
 * s5=0
 * s6=keine Dateien
 * s7=1
 * s8=eine Datei
 * s9=2
 * s10={0,number} Dateien
 * s11=Die Formatierung warf eine Exception: {0}
 * s12=FEHLER
 * s13=Ergebnis
 * s14=Dialog
 * s15=Auswahlkriterium
 * s16=1,3
 * </pre>
 *
 * @see ResourceBundle
 * @see ListResourceBundle
 * @see Properties#load()
 * @author Jochen Hoenicke */
public class PropertyResourceBundle extends ResourceBundle
{
  Properties properties;

  /**
   * Creates a new property resource bundle.
   * @param stream An input stream, where the resources are read from.
   */
  public PropertyResourceBundle(java.io.InputStream stream)
    throws java.io.IOException
  {
    properties = new Properties();
    properties.load(stream);
  }

  /**
   * Called by <code>getObject</code> when a resource is needed.  This
   * returns the resource given by the key.
   * @param key The key of the resource.
   * @return The resource for the key or null if it doesn't exists.
   */
  public Object handleGetObject(String key)
  {
    return properties.getProperty(key);
  }

  /**
   * This method should return all keys for which a resource exists.
   * @return An enumeration of the keys.
   */
  public Enumeration getKeys()
  {
    // We must also return the keys of our parent.
    if (parent != null)
      {
	return new DoubleEnumeration(properties.propertyNames(),
				     parent.getKeys());
      }
    return properties.propertyNames();
  }
}