Merchant API

{
  "outTradeNo": "ORD20240101001",
  "amount": 500.00,
  "currency": "EUR",
  "payType": "CREDIT_CARD",
  "notifyUrl": "https://merchant.com/notify",
  "returnUrl": "https://merchant.com/return",
  "customerName": "John",
  "customerPhone": "9876543210",
  "customerEmail": "john@example.com",
  "cardInfo": {
    "number": "4111111111111111",
    "expireMonth": "12",
    "expireYear": "2026",
    "cvv": "123",
    "name": "John"
  }
}

{
  "outTradeNo": "ORD20240101001"
}

{
  "currency": "INR"
}

// POST to notifyUrl
{
  "tradeId": "T20240101120000001",
  "outTradeNo": "ORD20240101001",
  "tradeStatus": "SUCCESS",
  "tradeAmount": 500.00,
  "merchantAmount": 485.00,
  "currency": "INR"
}

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.*;
import java.security.spec.PKCS8EncodedKeySpec;
import java.util.Arrays;
import java.util.Base64;

public class OpenApiClient {

    /** AES/CBC/PKCS5Padding encrypt */
    public static String aesEncrypt(String plainText, String aesKeyBase64) throws Exception {
        byte[] keyBytes = Base64.getDecoder().decode(aesKeyBase64);
        SecretKeySpec keySpec = new SecretKeySpec(keyBytes, "AES");
        IvParameterSpec iv = new IvParameterSpec(Arrays.copyOf(keyBytes, 16));
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, keySpec, iv);
        return Base64.getEncoder().encodeToString(
            cipher.doFinal(plainText.getBytes("UTF-8")));
    }

    /** AES/CBC/PKCS5Padding decrypt */
    public static String aesDecrypt(String cipherBase64, String aesKeyBase64) throws Exception {
        byte[] keyBytes = Base64.getDecoder().decode(aesKeyBase64);
        SecretKeySpec keySpec = new SecretKeySpec(keyBytes, "AES");
        IvParameterSpec iv = new IvParameterSpec(Arrays.copyOf(keyBytes, 16));
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.DECRYPT_MODE, keySpec, iv);
        return new String(
            cipher.doFinal(Base64.getDecoder().decode(cipherBase64)), "UTF-8");
    }

    /** SHA256withRSA sign */
    public static String rsaSign(String data, String privateKeyPem) throws Exception {
        String key = privateKeyPem
            .replace("-----BEGIN PRIVATE KEY-----", "")
            .replace("-----END PRIVATE KEY-----", "")
            .replaceAll("\\s+", "");
        byte[] keyBytes = Base64.getDecoder().decode(key);
        PKCS8EncodedKeySpec spec = new PKCS8EncodedKeySpec(keyBytes);
        PrivateKey privKey = KeyFactory.getInstance("RSA").generatePrivate(spec);
        Signature signature = Signature.getInstance("SHA256withRSA");
        signature.initSign(privKey);
        signature.update(data.getBytes("UTF-8"));
        return Base64.getEncoder().encodeToString(signature.sign());
    }

    /** Build and send API request */
    public static void example() throws Exception {
        String merchantNo    = "M20240101001";
        String aesKey        = "your-aes-key-base64";
        String merchantPK    = "-----BEGIN PRIVATE KEY-----\n...\n-----END PRIVATE KEY-----";

        // 1. Business parameters
        String bizJson = "{\"outTradeNo\":\"ORD001\",\"amount\":500,\"currency\":\"EUR\"}";

        // 2. AES encrypt
        String encryptedBody = aesEncrypt(bizJson, aesKey);

        // 3. Build sign string
        String requestId = "req_" + System.currentTimeMillis();
        String timestamp = String.valueOf(System.currentTimeMillis());
        String signData  = String.join("|",
            merchantNo, "1.0", requestId, timestamp, encryptedBody);

        // 4. RSA sign
        String sign = rsaSign(signData, merchantPK);

        // 5. Send HTTP POST with headers; Body is {"payload": "<encrypted string>"}
        String requestBody = "{\"payload\":\"" + encryptedBody + "\"}";
        // Send requestBody as the HTTP POST body
    }
}