/*
* Copyright (c) 1995, 2021, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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*/
package java.net;
import java.io.UnsupportedEncodingException;
import java.io.CharArrayWriter;
import java.nio.charset.Charset;
import java.nio.charset.IllegalCharsetNameException;
import java.nio.charset.UnsupportedCharsetException ;
import java.util.BitSet;
import java.util.Objects;
import jdk.internal.util.StaticProperty;
/**
* Utility class for HTML form encoding. This class contains static methods
* for converting a String to the <CODE>application/x-www-form-urlencoded</CODE> MIME
* format. For more information about HTML form encoding, consult the HTML
* <A HREF="http://www.w3.org/TR/html4/">specification</A>.
*
* <p>
* When encoding a String, the following rules apply:
*
* <ul>
* <li>The alphanumeric characters "{@code a}" through
* "{@code z}", "{@code A}" through
* "{@code Z}" and "{@code 0}"
* through "{@code 9}" remain the same.
* <li>The special characters "{@code .}",
* "{@code -}", "{@code *}", and
* "{@code _}" remain the same.
* <li>The space character " " is
* converted into a plus sign "{@code +}".
* <li>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
* "<i>{@code %xy}</i>", where <i>xy</i> 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 charset is used.
* </ul>
*
* <p>
* 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).
*
* @see Charset#defaultCharset()
*
* @author Herb Jellinek
* @since 1.0
*/
public class URLEncoder {
static BitSet dontNeedEncoding;
static final int caseDiff = (
'a' -
'A');
static String dfltEncName;
static {
/* 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, Internet 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 = StaticProperty.fileEncoding();
}
/**
* You can't call the constructor.
*/
private URLEncoder() { }
/**
* Translates a string into {@code x-www-form-urlencoded}
* format. This method uses the default charset
* as the encoding scheme to obtain the bytes for unsafe characters.
*
* @param s {@code String} to be translated.
* @deprecated The resulting string may vary depending on the
* default charset. Instead, use the encode(String,String)
* method to specify the encoding.
* @return the translated {@code String}.
*/
@Deprecated
public static String encode(String s) {
String str =
null;
try {
str = encode(s, dfltEncName);
}
catch (UnsupportedEncodingException e) {
// The system should always have the default charset
}
return str;
}
/**
* Translates a string into {@code application/x-www-form-urlencoded}
* format using a specific encoding scheme.
* <p>
* This method behaves the same as {@linkplain #encode(String s, Charset charset)}
* except that it will {@linkplain Charset#forName look up the charset}
* using the given encoding name.
*
* @param s {@code String} to be translated.
* @param enc The name of a supported
* <a href="../lang/package-summary.html#charenc">character
* encoding</a>.
* @return the translated {@code String}.
* @throws UnsupportedEncodingException
* If the named encoding is not supported
* @see URLDecoder#decode(java.lang.String, java.lang.String)
* @since 1.4
*/
public static String encode(String s, String enc)
throws UnsupportedEncodingException {
if (enc ==
null) {
throw new NullPointerException(
"charsetName");
}
try {
Charset charset = Charset.forName(enc);
return encode(s, charset);
}
catch (IllegalCharsetNameException | UnsupportedCharsetException e) {
throw new UnsupportedEncodingException(enc);
}
}
/**
* Translates a string into {@code application/x-www-form-urlencoded}
* format using a specific {@linkplain Charset Charset}.
* This method uses the supplied charset to obtain the bytes for unsafe
* characters.
* <p>
* <em><strong>Note:</strong> The <a href=
* "http://www.w3.org/TR/html40/appendix/notes.html#non-ascii-chars">
* World Wide Web Consortium Recommendation</a> states that
* UTF-8 should be used. Not doing so may introduce incompatibilities.</em>
*
* @param s {@code String} to be translated.
* @param charset the given charset
* @return the translated {@code String}.
* @throws NullPointerException if {@code s} or {@code charset} is {@code null}.
* @see URLDecoder#decode(java.lang.String, Charset)
* @since 10
*/
public static String encode(String s, Charset charset) {
Objects.requireNonNull(charset,
"charset");
boolean needToChange =
false;
StringBuilder out =
new StringBuilder(s.length());
CharArrayWriter charArrayWriter =
new CharArrayWriter();
for (
int i = 0; i < s.length();) {
int c = 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);
i++;
}
else {
// convert to external encoding before hex conversion
do {
charArrayWriter.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 byte 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 = 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");
*/
charArrayWriter.write(d);
i++;
}
}
}
i++;
}
while (i < s.length() && !dontNeedEncoding.get((c = s.charAt(i))));
charArrayWriter.flush();
String str = charArrayWriter.toString();
byte[] ba = str.getBytes(charset);
for (
byte b : ba) {
out.append(
'%');
char ch = Character.forDigit((b >> 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(b & 0xF, 16);
if (Character.isLetter(ch)) {
ch -= caseDiff;
}
out.append(ch);
}
charArrayWriter.reset();
needToChange =
true;
}
}
return (needToChange? out.toString() : s);
}
}
