data要加密的数据，key密钥

public static String HMACSHA256(String data, String key) throws Exception {

       Mac sha256_HMAC = Mac.getInstance("HmacSHA256");

       SecretKeySpec secret_key = new SecretKeySpec(key.getBytes("UTF-8"), "HmacSHA256");

       sha256_HMAC.init(secret_key);

       byte[] array = sha256_HMAC.doFinal(data.getBytes("UTF-8"));

       StringBuilder sb = new StringBuilder();

       for (byte item : array) {

           sb.append(Integer.toHexString((item & 0xFF) | 0x100).substring(1, 3));

       }

       return sb.toString().toUpperCase();

   }