mari mari - 27 days ago 5
Java Question

How to send post request with x-www-form-urlencoded body

Request in postman

How in java send request with x-www-form-urlencoded header, actually I dont't undesrtand how to send body with a key-value, like at a screenshot.

I have tried this code:

String urlParameters =
cafedra_name+ data_to_send;
URL url;
HttpURLConnection connection = null;
try {
//Create connection
url = new URL(targetURL);
connection = (HttpURLConnection)url.openConnection();
connection.setRequestMethod("POST");
connection.setRequestProperty("Content-Type",
"application/x-www-form-urlencoded");

connection.setRequestProperty("Content-Length", "" +
Integer.toString(urlParameters.getBytes().length));
connection.setRequestProperty("Content-Language", "en-US");

connection.setUseCaches (false);
connection.setDoInput(true);
connection.setDoOutput(true);

//Send request
DataOutputStream wr = new DataOutputStream (
connection.getOutputStream ());
wr.writeBytes (urlParameters);
wr.flush ();
wr.close ();


But in responce i don't receive correct data.

Answer

As you set application/x-www-form-urlencoded as content type so data sent must be like this format.

String urlParameters  = "param1=data1&param2=data2&param3=data3";

Sending part now is quite straightforward.

byte[] postData = urlParameters.getBytes( StandardCharsets.UTF_8 );
int postDataLength = postData.length;
String request = "<Url here>";
URL url = new URL( request );
HttpURLConnection conn= (HttpURLConnection) url.openConnection();           
conn.setDoOutput(true);
conn.setInstanceFollowRedirects(false);
conn.setRequestMethod("POST");
conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); 
conn.setRequestProperty("charset", "utf-8");
conn.setRequestProperty("Content-Length", Integer.toString(postDataLength ));
conn.setUseCaches(false);
try(DataOutputStream wr = new DataOutputStream(conn.getOutputStream())) {
   wr.write( postData );
}

Or you can create a generic method to build key value pattern which is required for application/x-www-form-urlencoded.

 private String getDataString(HashMap<String, String> params) throws UnsupportedEncodingException{
        StringBuilder result = new StringBuilder();
        boolean first = true;
        for(Map.Entry<String, String> entry : params.entrySet()){
            if (first)
                first = false;
            else
                result.append("&");    
            result.append(URLEncoder.encode(entry.getKey(), "UTF-8"));
            result.append("=");
            result.append(URLEncoder.encode(entry.getValue(), "UTF-8"));
        }    
        return result.toString();
    }