cURL and HttpURLConnection - Post JSON Data

Question

How to post JSON data using HttpURLConnection? I am trying this:

HttpURLConnection httpcon = (HttpURLConnection) ((new URL("a url").openConnection()));
httpcon.setDoOutput(true);
httpcon.setRequestProperty("Content-Type", "application/json");
httpcon.setRequestProperty("Accept", "application/json");
httpcon.setRequestMethod("POST");
httpcon.connect();

StringReader reader = new StringReader("{'value': 7.5}");
OutputStream os = httpcon.getOutputStream();

char[] buffer = new char[4096];
int bytes_read;    
while((bytes_read = reader.read(buffer)) != -1) {
    os.write(buffer, 0, bytes_read);// I am getting compilation error here
}
os.close();

I am getting compilation error in line 14.

The cURL request is:

curl -H "Accept: application/json" \
-H "Content-Type: application/json" \
-d "{'value': 7.5}" \
"a URL"

Is this the way to handle cURL request? Any information will be very helpful to me.

Thanks.

Solution 1

OutputStream expects to work with bytes, and you're passing it characters. Try this:

HttpURLConnection httpcon = (HttpURLConnection) ((new URL("a url").openConnection()));
httpcon.setDoOutput(true);
httpcon.setRequestProperty("Content-Type", "application/json");
httpcon.setRequestProperty("Accept", "application/json");
httpcon.setRequestMethod("POST");
httpcon.connect();

byte[] outputBytes = "{'value': 7.5}".getBytes("UTF-8");
OutputStream os = httpcon.getOutputStream();
os.write(outputBytes);

os.close();

Solution 2

You may want to use the OutputStreamWriter class.

final String toWriteOut = "{'value': 7.5}";
final OutputStreamWriter osw = new OutputStreamWriter(connection.getOutputStream());
osw.write(toWriteOut);
osw.close();

Comments

[crowmagnumb]

Is it not possible to send a complex json object in this manner? For instance ... "{"points":[{"point":{"latitude":40.8195085182092,"longitude‌​":-73.75127574479318‌​},"description":"tes‌​t"},{"point":{"latit‌​ude":40.219508518209‌​2,"longitude":-74.75‌​127574479318},"descr‌​iption":"test2"}],"m‌​ode":"WALKING"}" ... is an object that I'm sending via this method and I get an HTTP Response Code of 500.

[user1002601]

@CrowMagnumb You should post a separate question. 500 means that the server has an internal error trying to process your request.

[crowmagnumb]

OK, I've done so here Thanks for the suggestion.

[Darpan]

what would be the benefit over OutputStream?