libjava/java/util/Properties.java

/* java.util.Properties
   Copyright (C) 1998, 1999, 2000 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 java.io.*;

/**
 * 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 character
 * <code>\</code><code>u00e4</code> is the german &auml;)
 * 
 * <pre>
 * s1=3
 * s2=MeineDisk
 * s3=3. M\<code></code>u00e4rz 96
 * s4=Die Diskette ''{1}'' enth\<code></code>u00e4lt {0} in {2}.
 * s5=0
 * s6=keine Dateien
 * s7=1
 * s8=eine Datei
 * s9=2
 * s10={0,number} Dateien
 * s11=Das Formatieren schlug fehl mit folgender Exception: {0}
 * s12=FEHLER
 * s13=Ergebnis
 * s14=Dialog
 * s15=Auswahlkriterium
 * s16=1,3
 * </pre>
 *
 * Although this is a sub class of a hash table, you should never
 * insert anything other than strings to this property, or several
 * methods, that need string keys and values, will fail.  To ensure
 * this, you should use the <code>get/setProperty</code> method instead
 * of <code>get/put</code>.
 *
 * @see PropertyResourceBundle
 * @author Jochen Hoenicke */
public class Properties extends Hashtable
{
  /**
   * The property list that contains default values for any keys not
   * in this property list.  
   */
  protected Properties defaults;

  private static final long serialVersionUID = 4112578634029874840L;

  /**
   * Creates a new empty property list.
   */
  public Properties()
  {
    this.defaults = null;
  }

  /**
   * Create a new empty property list with the specified default values.
   * @param defaults a Properties object containing the default values.
   */
  public Properties(Properties defaults)
  {
    this.defaults = defaults;
  }

  /**
   * Reads a property list from an input stream.  The stream should
   * have the following format: <br>
   *
   * An empty line or a line starting with <code>#</code> or
   * <code>!</code> is ignored.  An backslash (<code>\</code>) at the
   * end of the line makes the line continueing on the next line
   * (but make sure there is no whitespace after the backslash).
   * Otherwise, each line describes a key/value pair. <br>
   *
   * The chars up to the first whitespace, = or : are the key.  You
   * can include this caracters in the key, if you precede them with
   * a backslash (<code>\</code>). The key is followed by optional
   * whitespaces, optionally one <code>=</code> or <code>:</code>,
   * and optionally some more whitespaces.  The rest of the line is
   * the resource belonging to the key. <br>
   *
   * Escape sequences <code>\t, \n, \r, \\, \", \', \!, \#, \ </code>(a
   * space), and unicode characters with the
   * <code>\</code><code>u</code>xxxx notation are detected, and 
   * converted to the corresponding single character. <br>
   *
   * <pre>
   * # This is a comment
   * key     = value
   * k\:5      \ a string starting with space and ending with newline\n
   * # This is a multiline specification; note that the value contains
   * # no white space.
   * weekdays: Sunday,Monday,Tuesday,Wednesday,\
   *           Thursday,Friday,Saturday
   * # The safest way to include a space at the end of a value:
   * label   = Name:\<code></code>u0020
   * </pre>
   *
   * @param in the input stream
   * @exception IOException if an error occured when reading
   * from the input.  */
  public void load(InputStream inStream) throws IOException
  {
    BufferedReader reader =
      new BufferedReader(new InputStreamReader(inStream));
    String line;
    
    while ((line = reader.readLine()) != null)
      {
	char c = 0;
	int pos = 0;
	while (pos < line.length()
	       && Character.isWhitespace(c = line.charAt(pos)))
	  pos++;

	// If line is empty or begins with a comment character,
	// skip this line.
	if (pos == line.length() || c == '#' || c == '!')
	  continue;

	// The characaters up to the next Whitespace, ':', or '='
	// describe the key.  But look for escape sequences.
	StringBuffer key = new StringBuffer();
	while (pos < line.length()
	       && !Character.isWhitespace(c = line.charAt(pos++))
	       && c != '=' && c != ':')
	  {
	    if (c == '\\')
	      {
		if (pos == line.length())
		  {
		    // The line continues on the next line.
		    line = reader.readLine();
		    pos = 0;
		    while (pos < line.length()
			   && Character.isWhitespace(c = line.charAt(pos)))
		      pos++;
		  }
		else
		  {
		    c = line.charAt(pos++);
		    switch (c)
		      {
		      case 'n':
			key.append('\n');
			break;
		      case 't':
			key.append('\t');
			break;
		      case 'r':
			key.append('\r');
			break;
		      case 'u':
			if (pos + 4 <= line.length())
			  {
			    char uni = (char) Integer.parseInt
			      (line.substring(pos, pos + 4), 16);
			    key.append(uni);
			  }	// else throw exception?
			break;
		      default:
			key.append(c);
			break;
		      }
		  }
	      }
	    else
	      key.append(c);
	  }

	boolean isDelim = (c == ':' || c == '=');
	while (pos < line.length()
	       && Character.isWhitespace(c = line.charAt(pos)))
	  pos++;

	if (!isDelim && (c == ':' || c == '='))
	  {
	    pos++;
	    while (pos < line.length()
		   && Character.isWhitespace(c = line.charAt(pos)))
	      pos++;
	  }

	StringBuffer element = new StringBuffer(line.length() - pos);
	while (pos < line.length())
	  {
	    c = line.charAt(pos++);
	    if (c == '\\')
	      {
		if (pos == line.length())
		  {
		    // The line continues on the next line.
		    line = reader.readLine();
		    pos = 0;
		    while (pos < line.length()
			   && Character.isWhitespace(c = line.charAt(pos)))
		      pos++;
		    element.ensureCapacity(line.length() - pos +
					   element.length());
		  }
		else
		  {
		    c = line.charAt(pos++);
		    switch (c)
		      {
		      case 'n':
			element.append('\n');
			break;
		      case 't':
			element.append('\t');
			break;
		      case 'r':
			element.append('\r');
			break;
		      case 'u':
			if (pos + 4 <= line.length())
			  {
			    char uni = (char) Integer.parseInt
			      (line.substring(pos, pos + 4), 16);
			    element.append(uni);
			  }	// else throw exception?
			break;
		      default:
			element.append(c);
			break;
		      }
		  }
	      }
	    else
	      element.append(c);
	  }
	put(key.toString(), element.toString());
      }
  }

  /**
   * Calls <code>store(OutputStream out, String header)</code> and
   * ignores the IOException that may be thrown.
   * @deprecated use store instead.
   * @exception ClassCastException if this property contains any key or
   * value that isn't a string.
   */
  public void save(OutputStream out, String header)
  {
    try
      {
	store(out, header);
      }
    catch (IOException ex)
      {
      }
  }

  /**
   * Writes the key/value pairs to the given output stream. <br>
   *
   * If header is not null, this method writes a comment containing
   * the header as first line to the stream.  The next line (or first
   * line if header is null) contains a comment with the current date.
   * Afterwards the key/value pairs are written to the stream in the
   * following format. <br>
   *
   * Each line has the form <code>key = value</code>.  Newlines,
   * Returns and tabs are written as <code>\n,\t,\r</code> resp.
   * The characters <code>\, !, #, =</code> and <code>:</code> are
   * preceeded by a backslash.  Spaces are preceded with a backslash,
   * if and only if they are at the beginning of the key.  Characters
   * that are not in the ascii range 33 to 127 are written in the
   * <code>\</code><code>u</code>xxxx Form.
   *
   * @param out the output stream
   * @param header the header written in the first line, may be null.
   * @exception ClassCastException if this property contains any key or
   * value that isn't a string.
   */
  public void store(OutputStream out, String header) throws IOException
  {
    PrintWriter writer = new PrintWriter(out);
    if (header != null)
      writer.println("#" + header);
    writer.println("#" + new Date().toString());
    list(writer);
    writer.flush();
  }

  /**
   * Adds the given key/value pair to this properties.  This calls
   * the hashtable method put.
   * @param key the key for this property
   * @param value the value for this property
   * @return The old value for the given key.
   * @since JDK1.2 */
  public Object setProperty(String key, String value)
  {
    return put(key, value);
  }

  /**
   * 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 default or the default of
   * default, null is returned.
   * @param key The key for this property.
   * @param defaulValue A default value
   * @return The value for the given key, or null if not found. 
   * @exception ClassCastException if this property contains any key or
   * value that isn't a string.
   */
  public String getProperty(String key)
  {
    return getProperty(key, 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 default or the default of default, the 
   * specified defaultValue is returned.
   * @param key The key for this property.
   * @param defaulValue A default value
   * @return The value for the given key.
   * @exception ClassCastException if this property contains any key or
   * value that isn't a string.
   */
  public String getProperty(String key, String defaultValue)
  {
    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 defaultValue;
  }

  private final void addHashEntries(Hashtable base)
  {
    if (defaults != null)
      defaults.addHashEntries(base);
    Enumeration keys = keys();
    while (keys.hasMoreElements())
      base.put(keys.nextElement(), base);
  }

  /**
   * Returns an enumeration of all keys in this property list, including
   * the keys in the default property list.
   */
  public Enumeration propertyNames()
  {
    // We make a new Hashtable that holds all the keys.  Then we
    // return an enumeration for this hash.  We do this because we
    // don't want modifications to be reflected in the enumeration
    // (per JCL), and because there doesn't seem to be a
    // particularly better way to ensure that duplicates are
    // ignored.
    Hashtable t = new Hashtable();
    addHashEntries(t);
    return t.keys();
  }

  /**
   * Formats a key/value pair for output in a properties file.
   * See store for a description of the format.
   * @param key the key.
   * @param value the value.
   * @see #store
   */
  private String formatForOutput(String key, String value)
  {
    // This is a simple approximation of the expected line size.
    StringBuffer result =
      new StringBuffer(key.length() + value.length() + 16);
    boolean head = true;
    for (int i = 0; i < key.length(); i++)
      {
	char c = key.charAt(i);
	switch (c)
	  {
	  case '\n':
	    result.append("\\n");
	    break;
	  case '\r':
	    result.append("\\r");
	    break;
	  case '\t':
	    result.append("\\t");
	    break;
	  case '\\':
	    result.append("\\\\");
	    break;
	  case '!':
	    result.append("\\!");
	    break;
	  case '#':
	    result.append("\\#");
	    break;
	  case '=':
	    result.append("\\=");
	    break;
	  case ':':
	    result.append("\\:");
	    break;
	  case ' ':
	    result.append("\\ ");
	    break;
	  default:
	    if (c < 32 || c > '~')
	      {
		String hex = Integer.toHexString(c);
		result.append("\\u0000".substring(0, 6 - hex.length()));
		result.append(hex);
	      }
	    else
	        result.append(c);
	  }
	if (c != 32)
	  head = false;
      }
    result.append('=');
    head = true;
    for (int i = 0; i < value.length(); i++)
      {
	char c = value.charAt(i);
	switch (c)
	  {
	  case '\n':
	    result.append("\\n");
	    break;
	  case '\r':
	    result.append("\\r");
	    break;
	  case '\t':
	    result.append("\\t");
	    break;
	  case '\\':
	    result.append("\\\\");
	    break;
	  case '!':
	    result.append("\\!");
	    break;
	  case '#':
	    result.append("\\#");
	    break;
	  case ' ':
	    result.append(head ? "\\ " : " ");
	    break;
	  default:
	    if (c < 32 || c > '~')
	      {
		String hex = Integer.toHexString(c);
		result.append("\\u0000".substring(0, 6 - hex.length()));
		result.append(hex);
	      }
	    else
	      result.append(c);
	  }
	if (c != 32)
	  head = false;
      }
    return result.toString();
  }

  /**
   * Writes the key/value pairs to the given print stream.  They are
   * written in the way, described in the method store.
   * @param out the stream, where the key/value pairs are written to.
   * @exception ClassCastException if this property contains any key or
   * value that isn't a string.
   * @see #store
   */
  public void list(PrintStream out)
  {
    Enumeration keys = keys();
    Enumeration elts = elements();
    while (keys.hasMoreElements())
      {
	String key = (String) keys.nextElement();
	String elt = (String) elts.nextElement();
	String output = formatForOutput(key, elt);
	out.println(output);
      }
  }

  /**
   * Writes the key/value pairs to the given print writer.  They are
   * written in the way, described in the method store.
   * @param out the writer, where the key/value pairs are written to.
   * @exception ClassCastException if this property contains any key or
   * value that isn't a string.
   * @see #store
   * @see #list(java.io.PrintStream)
   * @since JDK1.1
   */
  public void list(PrintWriter out)
  {
    Enumeration keys = keys();
    Enumeration elts = elements();
    while (keys.hasMoreElements())
      {
	String key = (String) keys.nextElement();
	String elt = (String) elts.nextElement();
	String output = formatForOutput(key, elt);
	out.println(output);
      }
  }
}