Encode a path as required by the URL specification : URLDecoder « Network « Java Tutorial

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2. Network
3. URLDecoder

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.util.BitSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Map;
import java.util.StringTokenizer;

/*

 Derby - Class org.apache.derby.iapi.util.PropertyUtil

 Licensed to the Apache Software Foundation (ASF) under one or more
 contributor license agreements.  See the NOTICE file distributed with
 this work for additional information regarding copyright ownership.
 The ASF licenses this file to you under the Apache License, Version 2.0
 (the "License"); you may not use this file except in compliance with
 the License.  You may obtain a copy of the License at

 http://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.

 */

public class Main {


  /**
   * Array containing the safe characters set as defined by RFC 1738
   */
  private static BitSet safeCharacters;

  private static final char[] hexadecimal =
  {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
   'A', 'B', 'C', 'D', 'E', 'F'};

  static {
      safeCharacters = new BitSet(256);
      int i;
      // 'lowalpha' rule
      for (i = 'a'; i <= 'z'; i++) {
          safeCharacters.set(i);
      }
      // 'hialpha' rule
      for (i = 'A'; i <= 'Z'; i++) {
          safeCharacters.set(i);
      }
      // 'digit' rule
      for (i = '0'; i <= '9'; i++) {
          safeCharacters.set(i);
      }

      // 'safe' rule
      safeCharacters.set('$');
      safeCharacters.set('-');
      safeCharacters.set('_');
      safeCharacters.set('.');
      safeCharacters.set('+');

      // 'extra' rule
      safeCharacters.set('!');
      safeCharacters.set('*');
      safeCharacters.set('\'');
      safeCharacters.set('(');
      safeCharacters.set(')');
      safeCharacters.set(',');

      // special characters common to http: file: and ftp: URLs ('fsegment' and 'hsegment' rules)
      safeCharacters.set('/');
      safeCharacters.set(':');
      safeCharacters.set('@');
      safeCharacters.set('&');
      safeCharacters.set('=');
  }


  /**
   * Encode a path as required by the URL specification (<a href="http://www.ietf.org/rfc/rfc1738.txt">
   * RFC 1738</a>). This differs from <code>java.net.URLEncoder.encode()</code> which encodes according
   * to the <code>x-www-form-urlencoded</code> MIME format.
   *
   * @param path the path to encode
   * @return the encoded path
   */
  public static String encodePath(String path) {
     // stolen from org.apache.catalina.servlets.DefaultServlet ;)

      /**
       * Note: Here, ' ' should be encoded as "%20"
       * and '/' shouldn't be encoded.
       */

      int maxBytesPerChar = 10;
      StringBuffer rewrittenPath = new StringBuffer(path.length());
      ByteArrayOutputStream buf = new ByteArrayOutputStream(maxBytesPerChar);
      OutputStreamWriter writer;
      try {
          writer = new OutputStreamWriter(buf, "UTF8");
      } catch (Exception e) {
          e.printStackTrace();
          writer = new OutputStreamWriter(buf);
      }

      for (int i = 0; i < path.length(); i++) {
          int c = path.charAt(i);
          if (safeCharacters.get(c)) {
              rewrittenPath.append((char)c);
          } else {
              // convert to external encoding before hex conversion
              try {
                  writer.write(c);
                  writer.flush();
              } catch(IOException e) {
                  buf.reset();
                  continue;
              }
              byte[] ba = buf.toByteArray();
              for (int j = 0; j < ba.length; j++) {
                  // Converting each byte in the buffer
                  byte toEncode = ba[j];
                  rewrittenPath.append('%');
                  int low = (toEncode & 0x0f);
                  int high = ((toEncode & 0xf0) >> 4);
                  rewrittenPath.append(hexadecimal[high]);
                  rewrittenPath.append(hexadecimal[low]);
              }
              buf.reset();
          }
      }
      return rewrittenPath.toString();
  }




}