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 gnu.java.lang.CPStringBuilder;
041
042 import java.io.UnsupportedEncodingException;
043
044
045 /**
046 * This utility class contains static methods that converts a
047 * string encoded in the x-www-form-urlencoded format to the original
048 * text. The x-www-form-urlencoded format replaces certain disallowed
049 * characters with encoded equivalents. All upper case and lower case
050 * letters in the US alphabet remain as is, the space character (' ')
051 * is replaced with '+' sign, and all other characters are converted to a
052 * "%XX" format where XX is the hexadecimal representation of that character
053 * in a given character encoding (default is "UTF-8").
054 * <p>
055 * This method is very useful for decoding strings sent to CGI scripts
056 *
057 * Written using on-line Java Platform 1.2/1.4 API Specification.
058 * Status: Believed complete and correct.
059 *
060 * @since 1.2
061 *
062 * @author Warren Levy (warrenl@cygnus.com)
063 * @author Aaron M. Renn (arenn@urbanophile.com) (documentation comments)
064 * @author Mark Wielaard (mark@klomp.org)
065 */
066 public class URLDecoder
067 {
068 /**
069 * Public contructor. Note that this class has only static methods.
070 */
071 public URLDecoder()
072 {
073 }
074
075 /**
076 * This method translates the passed in string from x-www-form-urlencoded
077 * format using the default encoding "UTF-8" to decode the hex encoded
078 * unsafe characters.
079 *
080 * @param s the String to convert
081 *
082 * @return the converted String
083 *
084 * @deprecated
085 */
086 public static String decode(String s)
087 {
088 try
089 {
090 return decode(s, "UTF-8");
091 }
092 catch (UnsupportedEncodingException uee)
093 {
094 // Should never happen since UTF-8 encoding should always be supported
095 return s;
096 }
097 }
098
099 /**
100 * This method translates the passed in string from x-www-form-urlencoded
101 * format using the given character encoding to decode the hex encoded
102 * unsafe characters.
103 *
104 * This implementation will decode the string even if it contains
105 * unsafe characters (characters that should have been encoded) or if the
106 * two characters following a % do not represent a hex encoded byte.
107 * In those cases the unsafe character or the % character will be added
108 * verbatim to the decoded result.
109 *
110 * @param s the String to convert
111 * @param encoding the character encoding to use the decode the hex encoded
112 * unsafe characters
113 *
114 * @return the converted String
115 *
116 * @exception UnsupportedEncodingException If the named encoding is not
117 * supported
118 *
119 * @since 1.4
120 */
121 public static String decode(String s, String encoding)
122 throws UnsupportedEncodingException
123 {
124 // First convert all '+' characters to spaces.
125 String str = s.replace('+', ' ');
126
127 // Then go through the whole string looking for byte encoded characters
128 int i;
129 int start = 0;
130 byte[] bytes = null;
131 int length = str.length();
132 CPStringBuilder result = new CPStringBuilder(length);
133 while ((i = str.indexOf('%', start)) >= 0)
134 {
135 // Add all non-encoded characters to the result buffer
136 result.append(str.substring(start, i));
137 start = i;
138
139 // Get all consecutive encoded bytes
140 while ((i + 2 < length) && (str.charAt(i) == '%'))
141 i += 3;
142
143 // Decode all these bytes
144 if ((bytes == null) || (bytes.length < ((i - start) / 3)))
145 bytes = new byte[((i - start) / 3)];
146
147 int index = 0;
148 try
149 {
150 while (start < i)
151 {
152 String sub = str.substring(start + 1, start + 3);
153 bytes[index] = (byte) Integer.parseInt(sub, 16);
154 index++;
155 start += 3;
156 }
157 }
158 catch (NumberFormatException nfe)
159 {
160 // One of the hex encoded strings was bad
161 }
162
163 // Add the bytes as characters according to the given encoding
164 result.append(new String(bytes, 0, index, encoding));
165
166 // Make sure we skip to just after a % sign
167 // There might not have been enough encoded characters after the %
168 // or the hex chars were not actually hex chars (NumberFormatException)
169 if (start < length && s.charAt(start) == '%')
170 {
171 result.append('%');
172 start++;
173 }
174 }
175
176 // Add any characters left
177 if (start < str.length())
178 result.append(str.substring(start));
179
180 return result.toString();
181 }
182 } // class URLDecoder