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javaapihttppostreddit

Reddit api Oauth: Server returned HTTP response code: 411 for URL error

I'm trying to get an access token from https://www.reddit.com/api/v1/access_token. To do so I need to send a CLIENT_ID and a CLIENT_SECRET to the above URL. I did so using Postman:

enter image description here

As highlighted on the screenshot, I've sent a grant_type as a GET parameter with value client_credentials and an Authorization parameter with value Basic heregoestheencodedkeyandid. The reuest type was set as POST. It worked correctly - I got an access token in a JSON response.

However, when I try to do the same thing by means of Java, I receieve a Server returned HTTP response code: 411 error:

public class RedditExample {
        private static String loginLink = "https://www.reddit.com/api/v1/access_token";

 public static void main(String[] args)  {
                RedditExample redditExample = new RedditExample ();

                redditExample.login();
        }

public boolean login()  {
            try  {
                URL loginURL = new URL(loginLink + "?grant_type=client_credentials");
                HttpURLConnection connection = (HttpURLConnection) loginURL.openConnection();
                setupPOSTConnection(connection);

                InputStream input = connection.getInputStream();
                String inputString = new Scanner(input, "UTF-8").useDelimiter("\\Z").next();

                System.out.println(inputString);
            }

            catch (Exception e) {
                System.out.println(e.toString());
            }

            return true;
        }

private static void setupPOSTConnection(HttpURLConnection connection) throws Exception  {
            connection.setDoOutput(true);
            connection.setRequestMethod("POST");

            connection.setRequestProperty("Authorization", "Basic heregoestheencodedkeyandid");
            connection.connect();
        }
}

I'm not sure what I'm doing different here, compared to Postman, so any help would be appreciated.

EDIT: Here is what I tried adding:

connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");

connection.setDoInput(true); connection.setDoOutput(true); connection.setRequestProperty("Content-Length", "0"); connection.setRequestProperty("Content-Length", "10");

String userAgent = "test /u/someuser";
connection.setRequestProperty("User-Agent", userAgent);

Unfortunately, neither worked - the error is still the same.

Solution

  • Setting content-length explicitly is not taken by HttpUrlConnection. So just provide request body with no content.

    StringBuilder postDataBuilder = new StringBuilder();
        byte[] postData = postDataBuilder.toString().getBytes("UTF-8");

        OutputStream out = conn.getOutputStream();
        out.write(postData);
        out.close();

    So the method will be like this:-

    private static void setupPOSTConnection(HttpURLConnection connection) throws Exception  {
            connection.setDoOutput(true);
            connection.setRequestMethod("POST");

            connection.setRequestProperty("Authorization", "Basic heregoestheencodedkeyandid");
StringBuilder postDataBuilder = new StringBuilder();
        byte[] postData = postDataBuilder.toString().getBytes("UTF-8");

        OutputStream out = conn.getOutputStream();
        out.write(postData);
        out.close();
            connection.connect();
        }

    also i found another way of simply adding one line:- 

    private static void setupPOSTConnection(HttpURLConnection connection) throws Exception  {
                connection.setDoOutput(true);
                connection.setRequestMethod("POST");

                connection.setRequestProperty("Authorization", "Basic heregoestheencodedkeyandid");
    conn.setFixedLengthStreamingMode(0);
                connection.connect();
            }