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.

As a special exception, if you link this library with other files to
produce an executable, this library does not by itself cause the
resulting executable to be covered by the GNU General Public License.
This exception does not however invalidate any other reasons why the
executable file might be covered by the GNU General Public License. */


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();
  }
}