1. 当java报错 JCE cannot authenticate the provider BC
   需要引入jar包，在pom文件中加入

<dependency>
     <groupId>org.bouncycastle</groupId>
     <artifactId>bcprov-jdk15on</artifactId>
     <version>1.59</version>
</dependency>

2. 解密过程

 public static String decryptRefundNotifyToString(String reqInfo,String apiKey)
            throws GeneralSecurityException, IOException {
        try {

            Security.addProvider(new BouncyCastleProvider());

            String apiKeyMD5 = MD5Util.encode(apiKey).toLowerCase();

            SecretKeySpec key = new SecretKeySpec(apiKeyMD5.getBytes(), "AES");

            Cipher cipher = Cipher.getInstance("AES/ECB/PKCS7Padding","BC");

            cipher.init(Cipher.DECRYPT_MODE,key);

            return new String(cipher.doFinal(Base64.getDecoder().decode(reqInfo)), StandardCharsets.UTF_8);
        } catch (NoSuchAlgorithmException | NoSuchPaddingException e) {
            throw new IllegalStateException(e);
        }
    }