001    /* URLEncoder.java -- Class to convert strings to a properly encoded URL
002       Copyright (C) 1998, 1999, 2001, 2002, 2003 Free Software Foundation, Inc.
003    
004    This file is part of GNU Classpath.
005    
006    GNU Classpath is free software; you can redistribute it and/or modify
007    it under the terms of the GNU General Public License as published by
008    the Free Software Foundation; either version 2, or (at your option)
009    any later version.
010    
011    GNU Classpath is distributed in the hope that it will be useful, but
012    WITHOUT ANY WARRANTY; without even the implied warranty of
013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014    General Public License for more details.
015    
016    You should have received a copy of the GNU General Public License
017    along with GNU Classpath; see the file COPYING.  If not, write to the
018    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019    02110-1301 USA.
020    
021    Linking this library statically or dynamically with other modules is
022    making a combined work based on this library.  Thus, the terms and
023    conditions of the GNU General Public License cover the whole
024    combination.
025    
026    As a special exception, the copyright holders of this library give you
027    permission to link this library with independent modules to produce an
028    executable, regardless of the license terms of these independent
029    modules, and to copy and distribute the resulting executable under
030    terms of your choice, provided that you also meet, for each linked
031    independent module, the terms and conditions of the license of that
032    module.  An independent module is a module which is not derived from
033    or based on this library.  If you modify this library, you may extend
034    this exception to your version of the library, but you are not
035    obligated to do so.  If you do not wish to do so, delete this
036    exception statement from your version. */
037    
038    package java.net;
039    
040    import gnu.java.lang.CPStringBuilder;
041    
042    import java.io.UnsupportedEncodingException;
043    
044    
045    /*
046     * Written using on-line Java Platform 1.2/1.4 API Specification, as well
047     * as "The Java Class Libraries", 2nd edition (Addison-Wesley, 1998).
048     * Status:  Believed complete and correct.
049     */
050    
051    /**
052     * This utility class contains static methods that converts a
053     * string into a fully encoded URL string in x-www-form-urlencoded
054     * format.  This format replaces certain disallowed characters with
055     * encoded equivalents.  All upper case and lower case letters in the
056     * US alphabet remain as is, the space character (' ') is replaced with
057     * '+' sign, and all other characters are converted to a "%XX" format
058     * where XX is the hexadecimal representation of that character in a
059     * certain encoding (by default, the platform encoding, though the
060     * standard is "UTF-8").
061     * <p>
062     * This method is very useful for encoding strings to be sent to CGI scripts
063     *
064     * @author Aaron M. Renn (arenn@urbanophile.com)
065     * @author Warren Levy (warrenl@cygnus.com)
066     * @author Mark Wielaard (mark@klomp.org)
067     */
068    public class URLEncoder
069    {
070      /**
071       * This method translates the passed in string into x-www-form-urlencoded
072       * format using the default encoding.  The standard encoding is
073       * "UTF-8", and the two-argument form of this method should be used
074       * instead.
075       *
076       * @param s The String to convert
077       *
078       * @return The converted String
079       *
080       * @deprecated
081       */
082      public static String encode(String s)
083      {
084        try
085          {
086            // We default to 8859_1 for compatibility with the same
087            // default elsewhere in the library.
088            return encode(s, System.getProperty("file.encoding", "8859_1"));
089          }
090        catch (UnsupportedEncodingException uee)
091          {
092            // Should never happen since default should always be supported
093            return s;
094          }
095      }
096    
097      /**
098       * This method translates the passed in string into x-www-form-urlencoded
099       * format using the character encoding to hex-encode the unsafe characters.
100       *
101       * @param s The String to convert
102       * @param encoding The encoding to use for unsafe characters
103       *
104       * @return The converted String
105       *
106       * @exception UnsupportedEncodingException If the named encoding is not
107       * supported
108       *
109       * @since 1.4
110       */
111      public static String encode(String s, String encoding)
112        throws UnsupportedEncodingException
113      {
114        int length = s.length();
115        int start = 0;
116        int i = 0;
117    
118        CPStringBuilder result = new CPStringBuilder(length);
119        while (true)
120          {
121            while (i < length && isSafe(s.charAt(i)))
122              i++;
123    
124            // Safe character can just be added
125            result.append(s.substring(start, i));
126    
127            // Are we done?
128            if (i >= length)
129              return result.toString();
130            else if (s.charAt(i) == ' ')
131              {
132                result.append('+'); // Replace space char with plus symbol.
133                i++;
134              }
135            else
136              {
137                // Get all unsafe characters
138                start = i;
139                char c;
140                while (i < length && (c = s.charAt(i)) != ' ' && ! isSafe(c))
141                  i++;
142    
143                // Convert them to %XY encoded strings
144                String unsafe = s.substring(start, i);
145                byte[] bytes = unsafe.getBytes(encoding);
146                for (int j = 0; j < bytes.length; j++)
147                  {
148                    result.append('%');
149                    int val = bytes[j];
150                    result.append(hex.charAt((val & 0xf0) >> 4));
151                    result.append(hex.charAt(val & 0x0f));
152                  }
153              }
154            start = i;
155          }
156      }
157    
158      /**
159       * Private static method that returns true if the given char is either
160       * a uppercase or lowercase letter from 'a' till 'z', or a digit froim
161       * '0' till '9', or one of the characters '-', '_', '.' or '*'. Such
162       * 'safe' character don't have to be url encoded.
163       */
164      private static boolean isSafe(char c)
165      {
166        return ((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')
167               || (c >= '0' && c <= '9') || c == '-' || c == '_' || c == '.'
168               || c == '*');
169      }
170    
171      /**
172       * Private constructor that does nothing. Included to avoid a default
173       * public constructor being created by the compiler.
174       */
175      private URLEncoder()
176      {
177      }
178    
179      /**
180       * Used to convert to hex.  We don't use Integer.toHexString, since
181       * it converts to lower case (and the Sun docs pretty clearly
182       * specify upper case here), and because it doesn't provide a
183       * leading 0.
184       */
185      private static final String hex = "0123456789ABCDEF";
186    }