Parsing URL query parameters

Question

Hi all, I keep running into situations where I need to parse the parameters from the query string of a URL. I'm not using Servlets or anything like that.
After much frustration with not being able to find a decent parser, I wrote one myself, and thought I would offer it to others who might be fighting the same thing. If you use these, please keep the source code comments in place!
Here it is:
* Written by: Kevin Day, Trumpet, Inc. (c) 2003
* You are free to use this code as long as these comments
* remain in tact.
* Parse parameters from the query segment of a URL
* Pass in the query segment, and it returnes a MAP
* containing entries for each Name.
* Each map entry is a List of values (it is legal to
* have multiple name-value pairs in a URL query
* that have the same name!
     static public Map getParamsFromQuery(String q) throws InvalidParameterException{
          * Query, q, can be of the form:
          * <blank>
          * name
          * name=
          * name="value"
          * name="value"&
          * name="value"&name2
          * name="value"&name2="value2"
          * name="value"&name="value"
          * name="value & more"&name2="value"
          Map params = new HashMap();
          StringBuffer name = new StringBuffer();
          StringBuffer val = new StringBuffer();
          StringBuffer out = null;
          boolean inString = false;
          boolean readingName = true; // are we reading the name or the value?
          int i = -1;
          int qlen = q.length();
          out = name;
          while (i < qlen){
               char c = ++i < qlen ? q.charAt(i) : '&';
               if (inString){
                    if (c != '\"')
                         out.append(c);
                    else
                         inString = false;
               } else if (c == '&') {
                    String nameStr = cleanEscapes(name.toString());
                    String valStr = cleanEscapes(val.toString());
                    List valList = (List)params.get(nameStr);
                    if (valList == null){
                         valList = new LinkedList();
                         params.put(nameStr, valList);
                    valList.add(valStr);
                    name.setLength(0);
                    val.setLength(0);
                    out = name;
               } else if (c == '=') {
                    out = val;
               } else if (c == '\"') {
                    inString = true;
               } else {
                    out.append(c);
          if (inString) throw new InvalidParameterException("Unexpected end of query string " + q + " - Expected '\"' at position " + i);
          return params;
     static private String cleanEscapes(String s){
          try {
               return URLDecoder.decode(s, "UTF-8");
          } catch (UnsupportedEncodingException e) {
               e.printStackTrace();
          return s;
You'll also need to create a new Exception class called InvalidParameterException.
Cheers,
- Kevin

Answer 1

Because javax.servlet.* is not included in the
standard Java distribution. I am writing my own
mini-web server interface for applications and don'tSounds like an interesting project, have you thought about implementing the Servlet API (or a subset)? It is well known to developers, and I dont think it would require that much extra work, but that would depend on mini mini is of course =).
want to add that dependency nastiness just to get a
parser...OK, I was just curious.