Java URL Decode decodeIfNeeded(String s)

Description

Unfortunately we have code that mindlessly decoded URLs (FileDownloadWindow) which borked (in the case I discovered) magnet uris with encoded parameters (e.g.

License

Open Source License

Parameter

Parameter	Description
s	a parameter

Declaration

public static String decodeIfNeeded(String s) 

Method Source Code

//package com.java2s;
/*/* w ww.  j  av  a 2s. c o m*/
 * Created on Mar 21, 2006 3:09:00 PM
 * Copyright (C) Azureus Software, Inc, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program 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 for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

import java.io.UnsupportedEncodingException;
import java.net.*;

public class Main {
    /**
     * Unfortunately we have code that mindlessly decoded URLs (FileDownloadWindow) which borked (in the case I discovered) magnet uris with encoded
     * parameters (e.g. the &tr= parameter) - doing so screws stuff up later if, for example, the parameter included an encoded '&'
     * @param s
     * @return
     */

    public static String decodeIfNeeded(String s) {
        if (s == null) {

            return ("");
        }

        try {
            // of course someone prolly added the blind URLDecode for a reason so try and just deal with the borkage
            // which means looking for &a=b elements and ensure we don't URLDecode the 'b'

            // only have issues if there's a naked '?' there

            int q_pos = s.indexOf('?');
            int a_pos = s.indexOf('&');

            if (q_pos == -1 && a_pos == -1) {

                return (decode(s));
            }

            int start = Math.min(q_pos, a_pos);

            return (decode(s.substring(0, start)) + s.substring(start));

        } catch (Throwable e) {

            return (s);
        }
    }

    public static String decode(String s) {
        if (s == null) {
            return "";
        }
        try {
            try {
                return (URLDecoder.decode(s, "UTF-8"));

            } catch (IllegalArgumentException e) {

                // handle truncated encodings somewhat gracefully

                int pos = s.lastIndexOf("%");

                if (pos >= s.length() - 2) {

                    return (URLDecoder.decode(s.substring(0, pos), "UTF-8"));
                }

                throw (e);
            }
        } catch (UnsupportedEncodingException e) {

            return (URLDecoder.decode(s));
        }
    }
}

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