How to stream a JSON object to a HttpURLConnection POST request

Question

I can not see what is wrong with this code:

JSONObject msg;  //passed in as a parameter to this method

HttpURLConnection httpCon = (HttpURLConnection) url.openConnection();
httpCon.setDoOutput(true);
httpCon.setDoInput(true);
httpCon.setUseCaches(false);
httpCon.setRequestProperty( "Content-Type", "application/json" );
httpCon.setRequestProperty("Accept", "application/json");
httpCon.setRequestMethod("POST");
OutputStream os = httpCon.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os, "UTF-8");
msg.write(osw);
osw.flush();
osw.close();    
os.close();     //probably overkill

On the server, I am getting no post content at all, a zero length string.

Answer 1

Try

...
httpCon.setRequestMethod("POST");
httpCon.connect(); // Note the connect() here
...
OutputStream os = httpCon.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os, "UTF-8");
...    
osw.write(msg.toString());
osw.flush();
osw.close();

to send data.

to retrieve data try:

BufferedReader br = new BufferedReader(new InputStreamReader( httpCon.getInputStream(),"utf-8"));
String line = null;
while ((line = br.readLine()) != null) {
    sb.append(line + "\n");
}
br.close();
System.out.println(""+sb.toString());

Answer 2

 public String sendHTTPData(String urlpath, JSONObject json) {
        HttpURLConnection connection = null;
        try {
            URL url=new URL(urlpath);
            connection = (HttpURLConnection) url.openConnection();
            connection.setDoOutput(true);
            connection.setDoInput(true);
            connection.setRequestMethod("POST");
            connection.setRequestProperty("Content-Type", "application/json");
            connection.setRequestProperty("Accept", "application/json");
            OutputStreamWriter streamWriter = new OutputStreamWriter(connection.getOutputStream());
            streamWriter.write(json.toString());
            streamWriter.flush();
            StringBuilder stringBuilder = new StringBuilder();
            if (connection.getResponseCode() == HttpURLConnection.HTTP_OK){
                InputStreamReader streamReader = new InputStreamReader(connection.getInputStream());
                BufferedReader bufferedReader = new BufferedReader(streamReader);
                String response = null;
                while ((response = bufferedReader.readLine()) != null) {
                    stringBuilder.append(response + "\n");
                }
                bufferedReader.close();

                Log.d("test", stringBuilder.toString());
                return stringBuilder.toString();
            } else {
                Log.e("test", connection.getResponseMessage());
                return null;
            }
        } catch (Exception exception){
            Log.e("test", exception.toString());
            return null;
        } finally {
            if (connection != null){
                connection.disconnect();
            }
        }
    }`

call this methopd in doitbackground in asynctask

Answer 3

HttpURLConnection is cumbersome to use. With DavidWebb, a tiny wrapper around HttpURLConnection, you can write it like this:

JSONObject msg;  //passed in as a parameter to this method

Webb webb = Webb.create();
JSONObject result = webb.post("http://my-url/path/to/res")
    .useCaches(false)
    .body(msg)
    .ensureSuccess()
    .asJsonObject()
    .getBody();

If you don't like it, there is a list of alternative libraries on the link provided.

Why should we all write the same boilerplate code every day? BTW the code above is more readable and less error-prone. HttpURLConnection has an awful interface. This has to be wrapped!