Can't decode query in URL!!!

Question

On HTML page I have java script like this:
function subApp()
window.open("test.jsp?param="+escape("������������"));
When in test.jsp page I try to get query using java.util.Decoder.decode(request.getQueryString(), 'utf-8') I've got following exception: URLDecoder: Illegal hex characters in escape (%) pattern - For input string: "u0"
What is wrong in this example?

Answer 1

I have tried to get this parameter using request.getParameter("param") but i have got only NULL.
I looked src for java.net.URLDecoder and i think this problem occur because:
1. As you can see in JavaScript reference function "escape" doing following:
The escape method returns a string value (in Unicode format) that contains the contents of charstring. All spaces, punctuation, accented characters, and any other non-ASCII characters are replaced with %xx encoding, where xx is equivalent to the hexadecimal number representing the character. For example, a space is returned as "%20."
Characters with a value greater than 255 are stored using the %uxxxx format.
(This means if i input : location.href = "test.jsp?param="+escape(привет); in address bar i will have following url: test.jsp?param=%u0407%u0430%u0401%u045E%u0490%u0432 )
2. As you can see in src of java.net.URLDecoder sequence %uFFFF will throws exception:
     case '%':
          * Starting with this instance of %, process all
          * consecutive substrings of the form %xy. Each
          * substring %xy will yield a byte. Convert all
          * consecutive bytes obtained this way to whatever
          * character(s) they represent in the provided
          * encoding.
          try {
          // (numChars-i)/3 is an upper bound for the number
          // of remaining bytes
          byte[] bytes = new byte[(numChars-i)/3];
          int pos = 0;
          while ( ((i+2) < numChars) &&
               (c=='%')) {
               bytes[pos++] =
               (byte)Integer.parseInt(s.substring(i+1,i+3),16);
               i+= 3;
               if (i < numChars)
               c = s.charAt(i);
          // A trailing, incomplete byte encoding such as
          // "%x" will cause an exception to be thrown
          if ((i < numChars) && (c=='%'))
               throw new IllegalArgumentException(
          "URLDecoder: Incomplete trailing escape (%) pattern");
          sb.append(new String(bytes, 0, pos, enc));
          } catch (NumberFormatException e) {
          throw new IllegalArgumentException(
"URLDecoder: Illegal hex characters in escape (%) pattern - "
          + e.getMessage());
I think we have some mistakes or javaScript function is wrong or URLDecoder is wrong.