Pos Payment

                            
                                import com.google.gson.Gson;
                                import org.apache.commons.codec.binary.Hex;
                                import javax.crypto.Mac;
                                import javax.crypto.spec.SecretKeySpec;
                                import java.io.BufferedReader;
                                import java.io.InputStreamReader;
                                import java.io.OutputStream;
                                import java.net.HttpURLConnection;
                                import java.net.URL;
                                import java.nio.charset.StandardCharsets;
                                import java.util.TreeMap;
                                import java.util.UUID;

                                public class Pos {

                                    private static final String privateKey = "OPAYPRV1641***********926";

                                    private static final String endpoint = "https://testapi.opaycheckout.com";

                                    private static final String merchantId = "256622011275597";

                                    public static void main(String[] args) throws Exception {
                                        String addr = endpoint + "/api/v1/international/payment/create";
                                        Gson gson = new Gson();
                                        TreeMap order = new TreeMap<>();
                                        TreeMap amount = new TreeMap<>();
                                        amount.put("currency","NGN");
                                        amount.put("total",400);
                                        order.put("amount",amount);
                                        order.put("callbackUrl","https://testapi.opaycheckout.com/api/v1/international/print");
                                        order.put("country","NG");
                                        order.put("customerName","customerName");
                                        order.put("payMethod","Pos");
                                        TreeMap product = new TreeMap<>();
                                        product.put("description","dd");
                                        product.put("name","name");
                                        order.put("product",product);
                                        order.put("reference", UUID.randomUUID().toString());
                                        order.put("sn","N78101818218");
                                        order.put("userPhone","+1234567879");

                                        String requestBody = gson.toJson(order);
                                        System.out.println("--request:");
                                        System.out.println(requestBody);
                                        String oPaySignature = hmacSHA512(requestBody, privateKey);
                                        System.out.println("--signature:");
                                        System.out.println(oPaySignature);

                                        URL url = new URL(addr);
                                        HttpURLConnection con = (HttpURLConnection)url.openConnection();
                                        con.setRequestMethod("POST");
                                        con.setRequestProperty("Content-Type", "application/json; utf-8");
                                        con.setRequestProperty("Authorization", "Bearer "+oPaySignature);
                                        con.setRequestProperty("MerchantId", merchantId);
                                        con.setDoOutput(true);
                                        OutputStream os = con.getOutputStream();
                                        byte[] input = requestBody.getBytes(StandardCharsets.UTF_8);
                                        os.write(input, 0, input.length);
                                        BufferedReader br = new BufferedReader(new InputStreamReader(con.getInputStream(), StandardCharsets.UTF_8));
                                        StringBuilder response = new StringBuilder();
                                        String responseLine = null;
                                        while ((responseLine = br.readLine()) != null) {
                                            response.append(responseLine.trim());
                                        }

                                        System.out.println("--response:");
                                        System.out.println(response.toString());
                                        //close your stream and connection
                                    }

                                    public static String hmacSHA512(final String data, final String secureKey) throws Exception{
                                        byte[] bytesKey = secureKey.getBytes();
                                        final SecretKeySpec secretKey = new SecretKeySpec(bytesKey, "HmacSHA512");
                                        Mac mac = Mac.getInstance("HmacSHA512");
                                        mac.init(secretKey);
                                        final byte[] macData = mac.doFinal(data.getBytes());
                                        byte[] hex = new Hex().encode(macData);
                                        return new String(hex, StandardCharsets.UTF_8);
                                    }
                                }