Java - Send array of key-value pairs via HttpURLConnection

Question

I need to send an array of key-value pairs via HttpURLConnection and here's the catch - there could be many pairs having the same key and/or the same value, like so:

{[key1,val1], [key1,val2], [key2,val2] ... }

I tried the following but the problem is that it does not accommodate for multiple pairs having the same key but different values:

    Map<String, String> params) throws IOException {
    URL url = new URL(requestURL);
    httpConn = (HttpURLConnection) url.openConnection();
    httpConn.setUseCaches(false);

    httpConn.setDoInput(true); // true indicates the server returns response

    StringBuffer requestParams = new StringBuffer();

    if (params != null && params.size() > 0) {

        httpConn.setDoOutput(true); // true indicates POST request

        // creates the params string, encode them using URLEncoder
        Iterator<String> paramIterator = params.keySet().iterator();
        while (paramIterator.hasNext()) {
            String key = paramIterator.next();
            String value = params.get(key);
            requestParams.append(URLEncoder.encode(key, "UTF-8"));
            requestParams.append("=").append(
                    URLEncoder.encode(value, "UTF-8"));
            requestParams.append("&");
        }

        // sends POST data
        OutputStreamWriter writer = new OutputStreamWriter(
                httpConn.getOutputStream());
        writer.write(requestParams.toString());
        writer.flush();
    }

Any suggestions on how this array of key-value pairs can be sent via POST?

NOTE: For reasons, I do not want to use anything from the org.apache.http package.

I guess you need a map which accepts multiple values for the same key. Try with Map<String, List<String>> map = new HashMap<String, List<String>>(); — Kvk
– Kvk, Commented Feb 21, 2015 at 4:32
I've also been looking for an answer in this regard. How do you add this key-value pairs to the request so that you can access them using something like php's $_POST — Oniya Daniel
– Oniya Daniel, Commented Jan 9, 2017 at 12:55

Astra Bear · Accepted Answer · 2015-02-21 05:19:32Z

1

send them as a numbered list of pairs eg

Iterator<String> paramIterator = params.keySet().iterator();
        int i = 0;
        while (paramIterator.hasNext()) {
            String key = "k"+i;
            String value = paramIterator.next()+","+params.get(key);
            requestParams.append(URLEncoder.encode(key, "UTF-8"));
            requestParams.append("=").append(
                    URLEncoder.encode(value, "UTF-8"));
            requestParams.append("&");
            i++;

        }

what you do at the server end is another matter and depends on what you are trying to achieve.

answered Feb 21, 2015 at 5:19

Astra Bear

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