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1 /* |
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2 * Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved. |
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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4 * |
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5 * This code is free software; you can redistribute it and/or modify it |
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6 * under the terms of the GNU General Public License version 2 only, as |
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7 * published by the Free Software Foundation. Oracle designates this |
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8 * particular file as subject to the "Classpath" exception as provided |
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9 * by Oracle in the LICENSE file that accompanied this code. |
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10 * |
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11 * This code is distributed in the hope that it will be useful, but WITHOUT |
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12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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14 * version 2 for more details (a copy is included in the LICENSE file that |
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15 * accompanied this code). |
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16 * |
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17 * You should have received a copy of the GNU General Public License version |
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18 * 2 along with this work; if not, write to the Free Software Foundation, |
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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20 * |
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21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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22 * or visit www.oracle.com if you need additional information or have any |
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23 * questions. |
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24 */ |
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25 |
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26 package java.net; |
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27 |
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28 import java.io.*; |
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29 |
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30 /** |
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31 * Utility class for HTML form decoding. This class contains static methods |
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32 * for decoding a String from the <CODE>application/x-www-form-urlencoded</CODE> |
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33 * MIME format. |
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34 * <p> |
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35 * The conversion process is the reverse of that used by the URLEncoder class. It is assumed |
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36 * that all characters in the encoded string are one of the following: |
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37 * "{@code a}" through "{@code z}", |
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38 * "{@code A}" through "{@code Z}", |
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39 * "{@code 0}" through "{@code 9}", and |
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40 * "{@code -}", "{@code _}", |
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41 * "{@code .}", and "{@code *}". The |
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42 * character "{@code %}" is allowed but is interpreted |
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43 * as the start of a special escaped sequence. |
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44 * <p> |
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45 * The following rules are applied in the conversion: |
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46 * |
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47 * <ul> |
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48 * <li>The alphanumeric characters "{@code a}" through |
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49 * "{@code z}", "{@code A}" through |
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50 * "{@code Z}" and "{@code 0}" |
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51 * through "{@code 9}" remain the same. |
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52 * <li>The special characters "{@code .}", |
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53 * "{@code -}", "{@code *}", and |
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54 * "{@code _}" remain the same. |
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55 * <li>The plus sign "{@code +}" is converted into a |
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56 * space character " " . |
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57 * <li>A sequence of the form "<i>{@code %xy}</i>" will be |
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58 * treated as representing a byte where <i>xy</i> is the two-digit |
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59 * hexadecimal representation of the 8 bits. Then, all substrings |
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60 * that contain one or more of these byte sequences consecutively |
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61 * will be replaced by the character(s) whose encoding would result |
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62 * in those consecutive bytes. |
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63 * The encoding scheme used to decode these characters may be specified, |
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64 * or if unspecified, the default encoding of the platform will be used. |
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65 * </ul> |
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66 * <p> |
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67 * There are two possible ways in which this decoder could deal with |
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68 * illegal strings. It could either leave illegal characters alone or |
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69 * it could throw an {@link java.lang.IllegalArgumentException}. |
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70 * Which approach the decoder takes is left to the |
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71 * implementation. |
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72 * |
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73 * @author Mark Chamness |
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74 * @author Michael McCloskey |
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75 * @since 1.2 |
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76 */ |
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77 |
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78 public class URLDecoder { |
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79 |
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80 // The platform default encoding |
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81 static String dfltEncName = URLEncoder.dfltEncName; |
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82 |
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83 /** |
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84 * Decodes a {@code x-www-form-urlencoded} string. |
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85 * The platform's default encoding is used to determine what characters |
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86 * are represented by any consecutive sequences of the form |
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87 * "<i>{@code %xy}</i>". |
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88 * @param s the {@code String} to decode |
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89 * @deprecated The resulting string may vary depending on the platform's |
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90 * default encoding. Instead, use the decode(String,String) method |
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91 * to specify the encoding. |
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92 * @return the newly decoded {@code String} |
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93 */ |
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94 @Deprecated |
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95 public static String decode(String s) { |
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96 |
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97 String str = null; |
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98 |
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99 try { |
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100 str = decode(s, dfltEncName); |
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101 } catch (UnsupportedEncodingException e) { |
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102 // The system should always have the platform default |
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103 } |
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104 |
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105 return str; |
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106 } |
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107 |
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108 /** |
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109 * Decodes an {@code application/x-www-form-urlencoded} string using |
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110 * a specific encoding scheme. |
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111 * The supplied encoding is used to determine |
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112 * what characters are represented by any consecutive sequences of the |
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113 * form "<i>{@code %xy}</i>". |
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114 * <p> |
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115 * <em><strong>Note:</strong> The <a href= |
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116 * "http://www.w3.org/TR/html40/appendix/notes.html#non-ascii-chars"> |
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117 * World Wide Web Consortium Recommendation</a> states that |
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118 * UTF-8 should be used. Not doing so may introduce |
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119 * incompatibilities.</em> |
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120 * |
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121 * @param s the {@code String} to decode |
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122 * @param enc The name of a supported |
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123 * <a href="../lang/package-summary.html#charenc">character |
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124 * encoding</a>. |
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125 * @return the newly decoded {@code String} |
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126 * @exception UnsupportedEncodingException |
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127 * If character encoding needs to be consulted, but |
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128 * named character encoding is not supported |
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129 * @see URLEncoder#encode(java.lang.String, java.lang.String) |
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130 * @since 1.4 |
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131 */ |
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132 public static String decode(String s, String enc) |
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133 throws UnsupportedEncodingException{ |
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134 |
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135 boolean needToChange = false; |
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136 int numChars = s.length(); |
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137 StringBuilder sb = new StringBuilder(numChars > 500 ? numChars / 2 : numChars); |
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138 int i = 0; |
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139 |
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140 if (enc.length() == 0) { |
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141 throw new UnsupportedEncodingException ("URLDecoder: empty string enc parameter"); |
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142 } |
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143 |
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144 char c; |
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145 byte[] bytes = null; |
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146 while (i < numChars) { |
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147 c = s.charAt(i); |
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148 switch (c) { |
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149 case '+': |
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150 sb.append(' '); |
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151 i++; |
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152 needToChange = true; |
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153 break; |
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154 case '%': |
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155 /* |
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156 * Starting with this instance of %, process all |
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157 * consecutive substrings of the form %xy. Each |
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158 * substring %xy will yield a byte. Convert all |
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159 * consecutive bytes obtained this way to whatever |
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160 * character(s) they represent in the provided |
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161 * encoding. |
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162 */ |
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163 |
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164 try { |
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165 |
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166 // (numChars-i)/3 is an upper bound for the number |
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167 // of remaining bytes |
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168 if (bytes == null) |
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169 bytes = new byte[(numChars-i)/3]; |
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170 int pos = 0; |
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171 |
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172 while ( ((i+2) < numChars) && |
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173 (c=='%')) { |
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174 int v = Integer.parseInt(s, i + 1, i + 3, 16); |
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175 if (v < 0) |
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176 throw new IllegalArgumentException("URLDecoder: Illegal hex characters in escape (%) pattern - negative value"); |
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177 bytes[pos++] = (byte) v; |
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178 i+= 3; |
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179 if (i < numChars) |
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180 c = s.charAt(i); |
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181 } |
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182 |
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183 // A trailing, incomplete byte encoding such as |
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184 // "%x" will cause an exception to be thrown |
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185 |
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186 if ((i < numChars) && (c=='%')) |
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187 throw new IllegalArgumentException( |
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188 "URLDecoder: Incomplete trailing escape (%) pattern"); |
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189 |
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190 sb.append(new String(bytes, 0, pos, enc)); |
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191 } catch (NumberFormatException e) { |
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192 throw new IllegalArgumentException( |
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193 "URLDecoder: Illegal hex characters in escape (%) pattern - " |
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194 + e.getMessage()); |
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195 } |
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196 needToChange = true; |
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197 break; |
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198 default: |
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199 sb.append(c); |
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200 i++; |
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201 break; |
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202 } |
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203 } |
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204 |
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205 return (needToChange? sb.toString() : s); |
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206 } |
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207 } |