Accessing Poloniex HTTP API with Java

Question

I try to connect to the poloniex.com API https://poloniex.com/support/api/ which says:

(All calls to the trading API are sent via HTTP POST to https://poloniex.com/tradingApi and must contain the following headers:

• Key - Your API key.
• Sign - The query's POST data signed by your key's "secret" according to the HMAC-SHA512 method.

Additionally, all queries must include a "nonce" POST parameter. The nonce parameter is an integer which must always be greater than the previous nonce used.)

But I always get

{"error":"Invalid
API key\/secret pair."}

My hmac512Digest works fine, I've checked it.

There must be something wrong in my code.

Can someone please Help?

   public class Pol2 {

    public static String POLONIEX_SECRET_KEY = "12345"; 
    public static String POLONIEX_API_KEY = "ABX"; 


    public static void main(String[] args) {
        try {
            accessPoloniex();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }


    public static final void accessPoloniex() throws IOException {

        final String nonce = String.valueOf(System.currentTimeMillis());

        String connectionString = "https://poloniex.com/tradingApi";

        String queryArgs = "command=returnBalances";

        String hmac512 = hmac512Digest(queryArgs, POLONIEX_SECRET_KEY);

        // Produce the output
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        Writer writer = new OutputStreamWriter(out, "UTF-8");
        writer.append(queryArgs);
        writer.flush();

        CloseableHttpClient httpClient = HttpClients.createDefault();
        HttpPost post = new HttpPost(connectionString);
        post.addHeader("Key", POLONIEX_API_KEY); //or setHeader?
        post.addHeader("Sign", hmac512);  //or setHeader?

        post.setEntity(new ByteArrayEntity(out.toByteArray()));
        List<NameValuePair> params = new ArrayList<>();

        params.add(new BasicNameValuePair("command", "returnBalances"));
        params.add(new BasicNameValuePair("nonce", nonce));

        CloseableHttpResponse response = null;
        Scanner in = null;
        try {
            post.setEntity(new UrlEncodedFormEntity(params));
            response = httpClient.execute(post);
            HttpEntity entity = response.getEntity();
            in = new Scanner(entity.getContent());
            while (in.hasNext()) {
                System.out.println(in.next());
            }
            EntityUtils.consume(entity);
        } finally {
            in.close();
            response.close();
        }
    }
}

Answer 1

I struggled with this myself and finally got it to work. Here's a very basic, working example:

public class PoloTest {

  public static void main(String[] args) throws NoSuchAlgorithmException, InvalidKeyException, ClientProtocolException, IOException {

    String key = "YOUR API KEY HERE";
    String secret = "YOUR API SECRET HERE";
    String url = "https://poloniex.com/tradingApi";
    String nonce = String.valueOf(System.currentTimeMillis());
    String queryArgs = "command=returnBalances&nonce=" + nonce;

    Mac shaMac = Mac.getInstance("HmacSHA512");
    SecretKeySpec keySpec = new SecretKeySpec(secret.getBytes(), "HmacSHA512");
    shaMac.init(keySpec);
    final byte[] macData = shaMac.doFinal(queryArgs.getBytes());
    String sign = Hex.encodeHexString(macData);

    CloseableHttpClient httpClient = HttpClients.createDefault();
    HttpPost post = new HttpPost(url);
    post.addHeader("Key", key); 
    post.addHeader("Sign", sign);

    List<NameValuePair> params = new ArrayList<NameValuePair>();
    params.add(new BasicNameValuePair("command", "returnBalances"));
    params.add(new BasicNameValuePair("nonce", nonce));
    post.setEntity(new UrlEncodedFormEntity(params));

    CloseableHttpResponse response = httpClient.execute(post);
    HttpEntity responseEntity = response.getEntity();
    System.out.println(response.getStatusLine());
    System.out.println(EntityUtils.toString(responseEntity));
  }

}