URLEncoderpublic class URLEncoder extends Object Utility class for HTML form encoding. This class contains static methods
for converting a String to the application/x-www-form-urlencoded MIME
format. For more information about HTML form encoding, consult the HTML
specification.
When encoding a String, the following rules apply:
- The alphanumeric characters "
a" through
"z", "A" through
"Z" and "0"
through "9" remain the same.
- The special characters "
.",
"-", "*", and
"_" remain the same.
- The space character "
" is
converted into a plus sign "+".
- All other characters are unsafe and are first converted into
one or more bytes using some encoding scheme. Then each byte is
represented by the 3-character string
"
%xy", where xy is the
two-digit hexadecimal representation of the byte.
The recommended encoding scheme to use is UTF-8. However,
for compatibility reasons, if an encoding is not specified,
then the default encoding of the platform is used.
For example using UTF-8 as the encoding scheme the string "The
string ü@foo-bar" would get converted to
"The+string+%C3%BC%40foo-bar" because in UTF-8 the character
ü is encoded as two bytes C3 (hex) and BC (hex), and the
character @ is encoded as one byte 40 (hex). |
| Fields Summary |
|---|
| static BitSet | dontNeedEncoding | | static final int | caseDiff | | static String | dfltEncName |
| Constructors Summary |
|---|
private URLEncoder()You can't call the constructor.
/* The list of characters that are not encoded has been
* determined as follows:
*
* RFC 2396 states:
* -----
* Data characters that are allowed in a URI but do not have a
* reserved purpose are called unreserved. These include upper
* and lower case letters, decimal digits, and a limited set of
* punctuation marks and symbols.
*
* unreserved = alphanum | mark
*
* mark = "-" | "_" | "." | "!" | "~" | "*" | "'" | "(" | ")"
*
* Unreserved characters can be escaped without changing the
* semantics of the URI, but this should not be done unless the
* URI is being used in a context that does not allow the
* unescaped character to appear.
* -----
*
* It appears that both Netscape and Internet Explorer escape
* all special characters from this list with the exception
* of "-", "_", ".", "*". While it is not clear why they are
* escaping the other characters, perhaps it is safest to
* assume that there might be contexts in which the others
* are unsafe if not escaped. Therefore, we will use the same
* list. It is also noteworthy that this is consistent with
* O'Reilly's "HTML: The Definitive Guide" (page 164).
*
* As a last note, Intenet Explorer does not encode the "@"
* character which is clearly not unreserved according to the
* RFC. We are being consistent with the RFC in this matter,
* as is Netscape.
*
*/
dontNeedEncoding = new BitSet(256);
int i;
for (i = 'a"; i <= 'z"; i++) {
dontNeedEncoding.set(i);
}
for (i = 'A"; i <= 'Z"; i++) {
dontNeedEncoding.set(i);
}
for (i = '0"; i <= '9"; i++) {
dontNeedEncoding.set(i);
}
dontNeedEncoding.set(' "); /* encoding a space to a + is done
* in the encode() method */
dontNeedEncoding.set('-");
dontNeedEncoding.set('_");
dontNeedEncoding.set('.");
dontNeedEncoding.set('*");
dfltEncName = (String)AccessController.doPrivileged (
new GetPropertyAction("file.encoding")
);
|
| Methods Summary |
|---|
| public static java.lang.String | encode(java.lang.String s)Translates a string into x-www-form-urlencoded
format. This method uses the platform's default encoding
as the encoding scheme to obtain the bytes for unsafe characters.
String str = null;
try {
str = encode(s, dfltEncName);
} catch (UnsupportedEncodingException e) {
// The system should always have the platform default
}
return str;
| | public static java.lang.String | encode(java.lang.String s, java.lang.String enc)Translates a string into application/x-www-form-urlencoded
format using a specific encoding scheme. This method uses the
supplied encoding scheme to obtain the bytes for unsafe
characters.
Note: The
World Wide Web Consortium Recommendation states that
UTF-8 should be used. Not doing so may introduce
incompatibilites.
boolean needToChange = false;
boolean wroteUnencodedChar = false;
int maxBytesPerChar = 10; // rather arbitrary limit, but safe for now
StringBuffer out = new StringBuffer(s.length());
ByteArrayOutputStream buf = new ByteArrayOutputStream(maxBytesPerChar);
OutputStreamWriter writer = new OutputStreamWriter(buf, enc);
for (int i = 0; i < s.length(); i++) {
int c = (int) s.charAt(i);
//System.out.println("Examining character: " + c);
if (dontNeedEncoding.get(c)) {
if (c == ' ") {
c = '+";
needToChange = true;
}
//System.out.println("Storing: " + c);
out.append((char)c);
wroteUnencodedChar = true;
} else {
// convert to external encoding before hex conversion
try {
if (wroteUnencodedChar) { // Fix for 4407610
writer = new OutputStreamWriter(buf, enc);
wroteUnencodedChar = false;
}
writer.write(c);
/*
* If this character represents the start of a Unicode
* surrogate pair, then pass in two characters. It's not
* clear what should be done if a bytes reserved in the
* surrogate pairs range occurs outside of a legal
* surrogate pair. For now, just treat it as if it were
* any other character.
*/
if (c >= 0xD800 && c <= 0xDBFF) {
/*
System.out.println(Integer.toHexString(c)
+ " is high surrogate");
*/
if ( (i+1) < s.length()) {
int d = (int) s.charAt(i+1);
/*
System.out.println("\tExamining "
+ Integer.toHexString(d));
*/
if (d >= 0xDC00 && d <= 0xDFFF) {
/*
System.out.println("\t"
+ Integer.toHexString(d)
+ " is low surrogate");
*/
writer.write(d);
i++;
}
}
}
writer.flush();
} catch(IOException e) {
buf.reset();
continue;
}
byte[] ba = buf.toByteArray();
for (int j = 0; j < ba.length; j++) {
out.append('%");
char ch = Character.forDigit((ba[j] >> 4) & 0xF, 16);
// converting to use uppercase letter as part of
// the hex value if ch is a letter.
if (Character.isLetter(ch)) {
ch -= caseDiff;
}
out.append(ch);
ch = Character.forDigit(ba[j] & 0xF, 16);
if (Character.isLetter(ch)) {
ch -= caseDiff;
}
out.append(ch);
}
buf.reset();
needToChange = true;
}
}
return (needToChange? out.toString() : s);
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