properties.java

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   * Following the listing, the output stream is flushed but left open.
   *
   * @param out the output stream
   * @param header the header written in the first line, may be null
   * @throws ClassCastException if this property contains any key or
   *         value that isn't a string
   * @throws IOException if writing to the stream fails
   * @throws NullPointerException if out is null
   * @since 1.2
   */
  public void store(OutputStream out, String header) throws IOException
  {
    // The spec says that the file must be encoded using ISO-8859-1.
    PrintWriter writer
      = new PrintWriter(new OutputStreamWriter(out, "ISO-8859-1"));
    if (header != null)
      writer.println("#" + header);
    writer.println ("#" + Calendar.getInstance ().getTime ());
    
    Iterator iter = entrySet ().iterator ();
    int i = size ();
    StringBuilder s = new StringBuilder (); // Reuse the same buffer.
    while (--i >= 0)
      {
        Map.Entry entry = (Map.Entry) iter.next ();
        formatForOutput ((String) entry.getKey (), s, true);
        s.append ('=');
        formatForOutput ((String) entry.getValue (), s, false);
        writer.println (s);
      }

    writer.flush ();
  }

  /**
   * Gets the property with the specified key in this property list.
   * If the key is not found, the default property list is searched.
   * If the property is not found in the default, null is returned.
   *
   * @param key The key for this property
   * @return the value for the given key, or null if not found
   * @throws ClassCastException if this property contains any key or
   *         value that isn't a string
   * @see #defaults
   * @see #setProperty(String, String)
   * @see #getProperty(String, String)
   */
  public String getProperty(String key)
  {
    Properties prop = this;
    // Eliminate tail recursion.
    do
      {
        String value = (String) prop.get(key);
        if (value != null)
          return value;
        prop = prop.defaults;
      }
    while (prop != null);
    return null;
  }

  /**
   * Gets the property with the specified key in this property list.  If
   * the key is not found, the default property list is searched.  If the
   * property is not found in the default, the specified defaultValue is
   * returned.
   *
   * @param key The key for this property
   * @param defaultValue A default value
   * @return The value for the given key
   * @throws ClassCastException if this property contains any key or
   *         value that isn't a string
   * @see #defaults
   * @see #setProperty(String, String)
   */
  public String getProperty(String key, String defaultValue)
  {
    String prop = getProperty(key);
    if (prop == null)
      prop = defaultValue;
    return prop;
  }

  /**
   * Returns an enumeration of all keys in this property list, including
   * the keys in the default property list.
   *
   * @return an Enumeration of all defined keys
   */
  public Enumeration propertyNames()
  {
    // We make a new Set that holds all the keys, then return an enumeration
    // for that. This prevents modifications from ruining the enumeration,
    // as well as ignoring duplicates.
    Properties prop = this;
    Set s = new HashSet();
    // Eliminate tail recursion.
    do
      {
        s.addAll(prop.keySet());
        prop = prop.defaults;
      }
    while (prop != null);
    return Collections.enumeration(s);
  }

  /**
   * Prints the key/value pairs to the given print stream.  This is 
   * mainly useful for debugging purposes.
   *
   * @param out the print stream, where the key/value pairs are written to
   * @throws ClassCastException if this property contains a key or a
   *         value that isn't a string
   * @see #list(PrintWriter)
   */
  public void list(PrintStream out)
  {
    PrintWriter writer = new PrintWriter (out);
    list (writer);
  }

  /**
   * Prints the key/value pairs to the given print writer.  This is
   * mainly useful for debugging purposes.
   *
   * @param out the print writer where the key/value pairs are written to
   * @throws ClassCastException if this property contains a key or a
   *         value that isn't a string
   * @see #list(PrintStream)
   * @since 1.1
   */
  public void list(PrintWriter out)
  {
    out.println ("-- listing properties --");

    Iterator iter = entrySet ().iterator ();
    int i = size ();
    while (--i >= 0)
      {
        Map.Entry entry = (Map.Entry) iter.next ();
        out.print ((String) entry.getKey () + "=");

        // JDK 1.3/1.4 restrict the printed value, but not the key,
        // to 40 characters, including the truncating ellipsis.
        String s = (String ) entry.getValue ();
        if (s != null && s.length () > 40)
          out.println (s.substring (0, 37) + "...");
        else
          out.println (s);
      }
    out.flush ();
  }

  /**
   * Formats a key or value for output in a properties file.
   * See store for a description of the format.
   *
   * @param str the string to format
   * @param buffer the buffer to add it to
   * @param key true if all ' ' must be escaped for the key, false if only
   *        leading spaces must be escaped for the value
   * @see #store(OutputStream, String)
   */
  private void formatForOutput(String str, StringBuilder buffer, boolean key)
  {
    if (key)
      {
        buffer.setLength(0);
        buffer.ensureCapacity(str.length());
      }
    else
      buffer.ensureCapacity(buffer.length() + str.length());
    boolean head = true;
    int size = str.length();
    for (int i = 0; i < size; i++)
      {
        char c = str.charAt(i);
        switch (c)
          {
          case '\n':
            buffer.append("\\n");
            break;
          case '\r':
            buffer.append("\\r");
            break;
          case '\t':
            buffer.append("\\t");
            break;
          case ' ':
            buffer.append(head ? "\\ " : " ");
            break;
          case '\\':
          case '!':
          case '#':
          case '=':
          case ':':
            buffer.append('\\').append(c);
            break;
          default:
            if (c < ' ' || c > '~')
              {
                String hex = Integer.toHexString(c);
                buffer.append("\\u0000".substring(0, 6 - hex.length()));
                buffer.append(hex);
              }
            else
              buffer.append(c);
          }
        if (c != ' ')
          head = key;
      }
  }

  /**
   * <p>
   * Encodes the properties as an XML file using the UTF-8 encoding.
   * The format of the XML file matches the DTD
   * <a href="http://java.sun.com/dtd/properties.dtd">
   * http://java.sun.com/dtd/properties.dtd</a>.
   * </p>
   * <p>
   * Invoking this method provides the same behaviour as invoking
   * <code>storeToXML(os, comment, "UTF-8")</code>.
   * </p>
   * 
   * @param os the stream to output to.
   * @param comment a comment to include at the top of the XML file, or
   *                <code>null</code> if one is not required.
   * @throws IOException if the serialization fails.
   * @throws NullPointerException if <code>os</code> is null.
   * @since 1.5
   */
  public void storeToXML(OutputStream os, String comment)
    throws IOException
  {
    storeToXML(os, comment, "UTF-8");
  }

  /**
   * <p>
   * Encodes the properties as an XML file using the supplied encoding.
   * The format of the XML file matches the DTD
   * <a href="http://java.sun.com/dtd/properties.dtd">
   * http://java.sun.com/dtd/properties.dtd</a>.
   * </p>
   * 
   * @param os the stream to output to.
   * @param comment a comment to include at the top of the XML file, or
   *                <code>null</code> if one is not required.
   * @param encoding the encoding to use for the XML output.
   * @throws IOException if the serialization fails.
   * @throws NullPointerException if <code>os</code> or <code>encoding</code>
   *                              is null.
   * @since 1.5
   */
  public void storeToXML(OutputStream os, String comment, String encoding)
    throws IOException
  {
    if (os == null)
      throw new NullPointerException("Null output stream supplied.");
    if (encoding == null)
      throw new NullPointerException("Null encoding supplied.");
    try
      {
	DOMImplementationRegistry registry = 
	  DOMImplementationRegistry.newInstance();
	DOMImplementation domImpl = registry.getDOMImplementation("LS 3.0");
	DocumentType doctype =
	  domImpl.createDocumentType("properties", null,
				     "http://java.sun.com/dtd/properties.dtd");
	Document doc = domImpl.createDocument(null, "properties", doctype);
	Element root = doc.getDocumentElement();
	if (comment != null)
	  {
	    Element commentElement = doc.createElement("comment");
	    commentElement.appendChild(doc.createTextNode(comment));
	    root.appendChild(commentElement);
	  }
	Iterator iterator = entrySet().iterator();
	while (iterator.hasNext())
	  {
	    Map.Entry entry = (Map.Entry) iterator.next();
	    Element entryElement = doc.createElement("entry");
	    entryElement.setAttribute("key", (String) entry.getKey());
	    entryElement.appendChild(doc.createTextNode((String)
							entry.getValue()));
	    root.appendChild(entryElement);
	  }
	DOMImplementationLS loadAndSave = (DOMImplementationLS) domImpl;
	LSSerializer serializer = loadAndSave.createLSSerializer();
	LSOutput output = loadAndSave.createLSOutput();
	output.setByteStream(os);
	output.setEncoding(encoding);
	serializer.write(doc, output);
      }
    catch (ClassNotFoundException e)
      {
	throw (IOException) 
	  new IOException("The XML classes could not be found.").initCause(e);
      }
    catch (InstantiationException e)
      {
	throw (IOException)
	  new IOException("The XML classes could not be instantiated.")
	  .initCause(e);
      }
    catch (IllegalAccessException e)
      {
	throw (IOException)
	  new IOException("The XML classes could not be accessed.")
	  .initCause(e);
      }
  }

  /**
   * <p>
   * Decodes the contents of the supplied <code>InputStream</code> as
   * an XML file, which represents a set of properties.  The format of
   * the XML file must match the DTD
   * <a href="http://java.sun.com/dtd/properties.dtd">
   * http://java.sun.com/dtd/properties.dtd</a>.
   * </p>
   *
   * @param in the input stream from which to receive the XML data.
   * @throws IOException if an I/O error occurs in reading the input data.
   * @throws InvalidPropertiesFormatException if the input data does not
   *                                          constitute an XML properties
   *                                          file.
   * @throws NullPointerException if <code>in</code> is null.
   * @since 1.5
   */
  public void loadFromXML(InputStream in)
    throws IOException, InvalidPropertiesFormatException
  {
    if (in == null)
      throw new NullPointerException("Null input stream supplied.");
    try
      {
        XMLInputFactory factory = XMLInputFactory.newInstance();
        // Don't resolve external entity references
        factory.setProperty("javax.xml.stream.isSupportingExternalEntities",
                            Boolean.FALSE);
        XMLStreamReader reader = factory.createXMLStreamReader(in);
        String name, key = null;
        StringBuffer buf = null;
        while (reader.hasNext())
          {
            switch (reader.next())
              {
              case XMLStreamConstants.START_ELEMENT:
                name = reader.getLocalName();
                if (buf == null && "entry".equals(name))
                  {
                    key = reader.getAttributeValue(null, "key");
                    if (key == null)
                      {
                        String msg = "missing 'key' attribute";
                        throw new InvalidPropertiesFormatException(msg);
                      }
                    buf = new StringBuffer();
                  }
                else if (!"properties".equals(name) && !"comment".equals(name))
                  {
                    String msg = "unexpected element name '" + name + "'";
                    throw new InvalidPropertiesFormatException(msg);
                  }
                break;
              case XMLStreamConstants.END_ELEMENT:
                name = reader.getLocalName();
                if (buf != null && "entry".equals(name))
                  {
                    put(key, buf.toString());
                    buf = null;
                  }
                else if (!"properties".equals(name) && !"comment".equals(name))
                  {
                    String msg = "unexpected element name '" + name + "'";
                    throw new InvalidPropertiesFormatException(msg);
                  }
                break;
              case XMLStreamConstants.CHARACTERS:
              case XMLStreamConstants.SPACE:
              case XMLStreamConstants.CDATA:
                if (buf != null)
                  buf.append(reader.getText());
                break;
              }
          }
        reader.close();
      }
    catch (XMLStreamException e)
      {
	throw (InvalidPropertiesFormatException)
	  new InvalidPropertiesFormatException("Error in parsing XML.").
	  initCause(e);
      }
  }

} // class Properties