application/x-www-form-urlencoded
* MIME format.
* * The conversion process is the reverse of that used by the URLEncoder class. It is assumed * that all characters in the encoded string are one of the following: * "{@code a}" through "{@code z}", * "{@code A}" through "{@code Z}", * "{@code 0}" through "{@code 9}", and * "{@code -}", "{@code _}", * "{@code .}", and "{@code *}". The * character "{@code %}" is allowed but is interpreted * as the start of a special escaped sequence. *
* The following rules are applied in the conversion: * *
* There are two possible ways in which this decoder could deal with * illegal strings. It could either leave illegal characters alone or * it could throw an {@code {@link java.lang.IllegalArgumentException}}. * Which approach the decoder takes is left to the * implementation. * * @author Mark Chamness * @author Michael McCloskey * @since 1.2 */ public class URLDecoder { // The platform default encoding static String dfltEncName = URLEncoder.dfltEncName; /** * Decodes a {@code x-www-form-urlencoded} string. * The platform's default encoding is used to determine what characters * are represented by any consecutive sequences of the form * "{@code %xy}". * @param s the {@code String} to decode * @deprecated The resulting string may vary depending on the platform's * default encoding. Instead, use the decode(String,String) method * to specify the encoding. * @return the newly decoded {@code String} */ @Deprecated public static String decode(String s) { String str = null; try { str = decode(s, dfltEncName); } catch (UnsupportedEncodingException e) { // The system should always have the platform default } return str; } /** * Decodes a {@code application/x-www-form-urlencoded} string using a specific * encoding scheme. * The supplied encoding is used to determine * what characters are represented by any consecutive sequences of the * form "{@code %xy}". *
* Note: The * World Wide Web Consortium Recommendation states that * UTF-8 should be used. Not doing so may introduce * incompatibilities. * * @param s the {@code String} to decode * @param enc The name of a supported * character * encoding. * @return the newly decoded {@code String} * @exception UnsupportedEncodingException * If character encoding needs to be consulted, but * named character encoding is not supported * @see URLEncoder#encode(java.lang.String, java.lang.String) * @since 1.4 */ public static String decode(String s, String enc) throws UnsupportedEncodingException{ boolean needToChange = false; int numChars = s.length(); StringBuffer sb = new StringBuffer(numChars > 500 ? numChars / 2 : numChars); int i = 0; if (enc.length() == 0) { throw new UnsupportedEncodingException ("URLDecoder: empty string enc parameter"); } char c; byte[] bytes = null; while (i < numChars) { c = s.charAt(i); switch (c) { case '+': sb.append(' '); i++; needToChange = true; break; case '%': /* * Starting with this instance of %, process all * consecutive substrings of the form %xy. Each * substring %xy will yield a byte. Convert all * consecutive bytes obtained this way to whatever * character(s) they represent in the provided * encoding. */ try { // (numChars-i)/3 is an upper bound for the number // of remaining bytes if (bytes == null) bytes = new byte[(numChars-i)/3]; int pos = 0; while ( ((i+2) < numChars) && (c=='%')) { // BEGIN Android-changed if (!isValidHexChar(s.charAt(i+1)) || !isValidHexChar(s.charAt(i+2))) { throw new IllegalArgumentException("URLDecoder: Illegal hex characters in escape (%) pattern : " + s.substring(i, i + 3)); } // END Android-changed int v = Integer.parseInt(s.substring(i+1,i+3),16); if (v < 0) throw new IllegalArgumentException("URLDecoder: Illegal hex characters in escape (%) pattern - negative value : " + s.substring(i, i + 3)); bytes[pos++] = (byte) v; i+= 3; if (i < numChars) c = s.charAt(i); } // A trailing, incomplete byte encoding such as // "%x" will cause an exception to be thrown if ((i < numChars) && (c=='%')) throw new IllegalArgumentException( "URLDecoder: Incomplete trailing escape (%) pattern"); sb.append(new String(bytes, 0, pos, enc)); } catch (NumberFormatException e) { throw new IllegalArgumentException( "URLDecoder: Illegal hex characters in escape (%) pattern - " + e.getMessage()); } needToChange = true; break; default: sb.append(c); i++; break; } } return (needToChange? sb.toString() : s); } // BEGIN Android-changed private static boolean isValidHexChar(char c) { return ('0' <= c && c <= '9') || ('a' <= c && c <= 'f') || ('A' <= c && c <= 'F'); } // END Android-changed }