001 /* URLDecoder.java -- Class to decode URL's from encoded form.
002 Copyright (C) 1998, 1999, 2000, 2001 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 java.io.UnsupportedEncodingException;
041
042
043 /**
044 * This utility class contains static methods that converts a
045 * string encoded in the x-www-form-urlencoded format to the original
046 * text. The x-www-form-urlencoded format replaces certain disallowed
047 * characters with encoded equivalents. All upper case and lower case
048 * letters in the US alphabet remain as is, the space character (' ')
049 * is replaced with '+' sign, and all other characters are converted to a
050 * "%XX" format where XX is the hexadecimal representation of that character
051 * in a given character encoding (default is "UTF-8").
052 * <p>
053 * This method is very useful for decoding strings sent to CGI scripts
054 *
055 * Written using on-line Java Platform 1.2/1.4 API Specification.
056 * Status: Believed complete and correct.
057 *
058 * @since 1.2
059 *
060 * @author Warren Levy (warrenl@cygnus.com)
061 * @author Aaron M. Renn (arenn@urbanophile.com) (documentation comments)
062 * @author Mark Wielaard (mark@klomp.org)
063 */
064 public class URLDecoder
065 {
066 /**
067 * Public contructor. Note that this class has only static methods.
068 */
069 public URLDecoder()
070 {
071 }
072
073 /**
074 * This method translates the passed in string from x-www-form-urlencoded
075 * format using the default encoding "UTF-8" to decode the hex encoded
076 * unsafe characters.
077 *
078 * @param s the String to convert
079 *
080 * @return the converted String
081 *
082 * @deprecated
083 */
084 public static String decode(String s)
085 {
086 try
087 {
088 return decode(s, "UTF-8");
089 }
090 catch (UnsupportedEncodingException uee)
091 {
092 // Should never happen since UTF-8 encoding should always be supported
093 return s;
094 }
095 }
096
097 /**
098 * This method translates the passed in string from x-www-form-urlencoded
099 * format using the given character encoding to decode the hex encoded
100 * unsafe characters.
101 *
102 * This implementation will decode the string even if it contains
103 * unsafe characters (characters that should have been encoded) or if the
104 * two characters following a % do not represent a hex encoded byte.
105 * In those cases the unsafe character or the % character will be added
106 * verbatim to the decoded result.
107 *
108 * @param s the String to convert
109 * @param encoding the character encoding to use the decode the hex encoded
110 * unsafe characters
111 *
112 * @return the converted String
113 *
114 * @exception UnsupportedEncodingException If the named encoding is not
115 * supported
116 *
117 * @since 1.4
118 */
119 public static String decode(String s, String encoding)
120 throws UnsupportedEncodingException
121 {
122 // First convert all '+' characters to spaces.
123 String str = s.replace('+', ' ');
124
125 // Then go through the whole string looking for byte encoded characters
126 int i;
127 int start = 0;
128 byte[] bytes = null;
129 int length = str.length();
130 StringBuffer result = new StringBuffer(length);
131 while ((i = str.indexOf('%', start)) >= 0)
132 {
133 // Add all non-encoded characters to the result buffer
134 result.append(str.substring(start, i));
135 start = i;
136
137 // Get all consecutive encoded bytes
138 while ((i + 2 < length) && (str.charAt(i) == '%'))
139 i += 3;
140
141 // Decode all these bytes
142 if ((bytes == null) || (bytes.length < ((i - start) / 3)))
143 bytes = new byte[((i - start) / 3)];
144
145 int index = 0;
146 try
147 {
148 while (start < i)
149 {
150 String sub = str.substring(start + 1, start + 3);
151 bytes[index] = (byte) Integer.parseInt(sub, 16);
152 index++;
153 start += 3;
154 }
155 }
156 catch (NumberFormatException nfe)
157 {
158 // One of the hex encoded strings was bad
159 }
160
161 // Add the bytes as characters according to the given encoding
162 result.append(new String(bytes, 0, index, encoding));
163
164 // Make sure we skip to just after a % sign
165 // There might not have been enough encoded characters after the %
166 // or the hex chars were not actually hex chars (NumberFormatException)
167 if (start < length && s.charAt(start) == '%')
168 {
169 result.append('%');
170 start++;
171 }
172 }
173
174 // Add any characters left
175 if (start < str.length())
176 result.append(str.substring(start));
177
178 return result.toString();
179 }
180 } // class URLDecoder