Java tutorial
/* * Copyright (c) 1995, 2017, 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 * or visit www.oracle.com if you need additional information or have any * questions. */ 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 sun.security.action.GetPropertyAction; /** * 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 encoding of the platform 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). * * @author Herb Jellinek * @since 1.0 */ public class URLEncoder { static BitSet dontNeedEncoding; static final int caseDiff = ('a' - 'A'); static String dfltEncName = null; 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 = GetPropertyAction.privilegedGetProperty("file.encoding"); } /** * You can't call the constructor. */ private URLEncoder() { } /** * Translates a string into {@code x-www-form-urlencoded} * format. This method uses the platform's default encoding * 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 platform's * default encoding. 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 platform default } 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 java.nio.charset.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 java.nio.charset.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, java.nio.charset.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 = (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); 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 = (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"); */ charArrayWriter.write(d); i++; } } } i++; } while (i < s.length() && !dontNeedEncoding.get((c = (int) s.charAt(i)))); charArrayWriter.flush(); String str = new String(charArrayWriter.toCharArray()); byte[] ba = str.getBytes(charset); 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); } charArrayWriter.reset(); needToChange = true; } } return (needToChange ? out.toString() : s); } }