Query String Manipulation in Java

Question

Does anyone have, or know of, a java class that I can use to manipulate query strings?

Essentially I'd like a class that I can simply give a query string to and then delete, add and modify query string KVP's.

Thanks in advance.

EDIT

In response to a comment made to this question, the query string will look something like this;

N=123+456+112&Ntt=koala&D=abc

So I'd like to pass this class the query string and say something like;

String[] N = queryStringClass.getParameter("N");

and then maybe

queryStringClass.setParameter("N", N);

and maybe queryStringClass.removeParameter("N");

Or something to that effect.

Answer 1

SOmething like this

 public static Map<String, String> getQueryMap(String query)  
 {  
     String[] params = query.split("&");  
     Map<String, String> map = new HashMap<String, String>();  
     for (String param : params)  
     {  
         String name = param.split("=")[0];  
         String value = param.split("=")[1];  
         map.put(name, value);  
     }  
     return map;  
 }  

To iterate the map simply:

 String query = url.getQuery();  
 Map<String, String> map = getQueryMap(query);  
 Set<String> keys = map.keySet();  
 for (String key : keys)  
 {  
    System.out.println("Name=" + key);  
    System.out.println("Value=" + map.get(key));  
 }  

Answer 2

You can also use Google Guava's Splitter.

String queryString = "variableA=89&variableB=100";
Map<String,String> queryParameters = Splitter
    .on("&")
    .withKeyValueSeparator("=")
    .split(queryString);
System.out.println(queryParameters.get("variableA"));

prints out

89

This I think is a very readable alternative to parsing it yourself.

Edit: As @raulk pointed out, this solution does not account for escaped characters. However, this may not be an issue because before you URL-Decode, the query string is guaranteed to not have any escaped characters that conflict with '=' and '&'. You can use this to your advantage in the following way.

Say that you must decode the following query string:

a=%26%23%25!)%23(%40!&b=%23%24(%40)%24%40%40))%24%23%5E*%26

which is URL encoded, then you are guaranteed that the '&' and '=' are specifically used for separating pairs and key from value, respectively, at which point you can use the Guava splitter to get:

a = %26%23%25!)%23(%40!
b = %23%24(%40)%24%40%40))%24%23%5E*%26

Once you have obtained the key-value pairs, then you can URL decode them separately.

a = &#%!)#(@!
b = #$(@)$@@))$#^*&

That should cover all cases.