URLDecoderpublic class URLDecoder extends Object Utility class for HTML form decoding. This class contains static methods
for decoding a String from the application/x-www-form-urlencoded
MIME format.
To 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:
"a" through "z",
"A" through "Z",
"0" through "9", and
"-", "_",
".", and "*". The
character "%" is allowed but is interpreted
as the start of a special escaped sequence.
The following rules are applied in the conversion:
- The alphanumeric characters "
a" through
"z", "A" through
"Z" and "0"
through "9" remain the same.
- The special characters "
.",
"-", "*", and
"_" remain the same.
- The plus sign "
+" is converted into a
space character " " .
- A sequence of the form "
%xy" will be
treated as representing a byte where xy is the two-digit
hexadecimal representation of the 8 bits. Then, all substrings
that contain one or more of these byte sequences consecutively
will be replaced by the character(s) whose encoding would result
in those consecutive bytes.
The encoding scheme used to decode these characters may be specified,
or if unspecified, the default encoding of the platform will be used.
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 {@link java.lang.IllegalArgumentException}.
Which approach the decoder takes is left to the
implementation. |
| Fields Summary |
|---|
| static String | dfltEncName |
| Methods Summary |
|---|
| public static java.lang.String | decode(java.lang.String s)Decodes a 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
"%xy".
String str = null;
try {
str = decode(s, dfltEncName);
} catch (UnsupportedEncodingException e) {
// The system should always have the platform default
}
return str;
| | public static java.lang.String | decode(java.lang.String s, java.lang.String enc)Decodes a 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 "%xy".
Note: The
World Wide Web Consortium Recommendation states that
UTF-8 should be used. Not doing so may introduce
incompatibilites.
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=='%")) {
bytes[pos++] =
(byte)Integer.parseInt(s.substring(i+1,i+3),16);
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);
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