Package java.net

Source Code of java.net.URLEncoder

/*
* @(#)URLEncoder.java  1.32 06/04/22
*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/

package java.net;

import java.io.ByteArrayOutputStream;
import java.io.BufferedWriter;
import java.io.OutputStreamWriter;
import java.io.IOException;
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.security.AccessController;
import java.security.PrivilegedAction;
import sun.security.action.GetBooleanAction;
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:
*
* <p>
* <ul>
* <li>The alphanumeric characters &quot;<code>a</code>&quot; through
*     &quot;<code>z</code>&quot;, &quot;<code>A</code>&quot; through
*     &quot;<code>Z</code>&quot; and &quot;<code>0</code>&quot;
*     through &quot;<code>9</code>&quot; remain the same.
* <li>The special characters &quot;<code>.</code>&quot;,
*     &quot;<code>-</code>&quot;, &quot;<code>*</code>&quot;, and
*     &quot;<code>_</code>&quot; remain the same.
* <li>The space character &quot;<code>&nbsp;</code>&quot; is
*     converted into a plus sign &quot;<code>+</code>&quot;.
* <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
*     &quot;<code>%<i>xy</i></code>&quot;, 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 &quot;The
* string &#252;@foo-bar&quot; would get converted to
* &quot;The+string+%C3%BC%40foo-bar&quot; because in UTF-8 the character
* &#252; is encoded as two bytes C3 (hex) and BC (hex), and the
* character @ is encoded as one byte 40 (hex).
*
* @author  Herb Jellinek
* @version 1.32, 04/22/06
* @since   JDK1.0
*/
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, 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")
      );
    }

    /**
     * You can't call the constructor.
     */
    private URLEncoder() { }

    /**
     * Translates a string into <code>x-www-form-urlencoded</code>
     * format. This method uses the platform's default encoding
     * as the encoding scheme to obtain the bytes for unsafe characters.
     *
     * @param   s   <code>String</code> 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</code>.
     */
    @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</code>
     * format using a specific encoding scheme. This method uses the
     * supplied encoding scheme 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
     * incompatibilites.</em>
     *
     * @param   s   <code>String</code> 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</code>.
     * @exception  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 {

  boolean needToChange = false;
        StringBuffer out = new StringBuffer(s.length());
  Charset charset;
  CharArrayWriter charArrayWriter = new CharArrayWriter();

  if (enc == null)
      throw new NullPointerException("charsetName");

  try {
      charset = Charset.forName(enc);
  } catch (IllegalCharsetNameException e) {
            throw new UnsupportedEncodingException(enc);
        } catch (UnsupportedCharsetException e) {
      throw new UnsupportedEncodingException(enc);
  }

  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 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");
        */
              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);
    }
}
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