Parsing query strings on Android

Question

Java EE has ServletRequest.getParameterValues().

On non-EE platforms, URL.getQuery() simply returns a string.

What\'s the normal way to properly parse the qu

Answer 1

I don't think there is one in JRE. You can find similar functions in other packages like Apache HttpClient. If you don't use any other packages, you just have to write your own. It's not that hard. Here is what I use,

public class QueryString {

 private Map<String, List<String>> parameters;

 public QueryString(String qs) {
  parameters = new TreeMap<String, List<String>>();

  // Parse query string
     String pairs[] = qs.split("&");
     for (String pair : pairs) {
            String name;
            String value;
            int pos = pair.indexOf('=');
            // for "n=", the value is "", for "n", the value is null
         if (pos == -1) {
          name = pair;
          value = null;
         } else {
       try {
        name = URLDecoder.decode(pair.substring(0, pos), "UTF-8");
              value = URLDecoder.decode(pair.substring(pos+1, pair.length()), "UTF-8");            
       } catch (UnsupportedEncodingException e) {
        // Not really possible, throw unchecked
           throw new IllegalStateException("No UTF-8");
       }
         }
         List<String> list = parameters.get(name);
         if (list == null) {
          list = new ArrayList<String>();
          parameters.put(name, list);
         }
         list.add(value);
     }
 }

 public String getParameter(String name) {        
  List<String> values = parameters.get(name);
  if (values == null)
   return null;

  if (values.size() == 0)
   return "";

  return values.get(0);
 }

 public String[] getParameterValues(String name) {        
  List<String> values = parameters.get(name);
  if (values == null)
   return null;

  return (String[])values.toArray(new String[values.size()]);
 }

 public Enumeration<String> getParameterNames() {  
  return Collections.enumeration(parameters.keySet()); 
 }

 public Map<String, String[]> getParameterMap() {
  Map<String, String[]> map = new TreeMap<String, String[]>();
  for (Map.Entry<String, List<String>> entry : parameters.entrySet()) {
   List<String> list = entry.getValue();
   String[] values;
   if (list == null)
    values = null;
   else
    values = (String[]) list.toArray(new String[list.size()]);
   map.put(entry.getKey(), values);
  }
  return map;
 } 
}