{
  "openId": "OPENID",
  "nickName": "NICKNAME",
  "gender": GENDER,
  "city": "CITY",
  "province": "PROVINCE",
  "country": "COUNTRY",
  "avatarUrl": "AVATARURL",
  "unionId": "UNIONID",
  "watermark":
  {
    "appid":"APPID",
    "timestamp":TIMESTAMP
  }
}

@RequestMapping(value = "/web/wechatapp/jscode2session", method = RequestMethod.POST)
  @ResponseBody
  public String getSessionByCode(@RequestBody String jsonStr, HttpServletRequest request) {
    JSONObject jsonObj = JSONObject.fromObject(jsonStr);
    String code = (String) jsonObj.get("code");
    JSONObject wechatAppUserInfo = jsonObj.getJSONObject("wechatAppUserInfo");
    String encryptedData = (String) wechatAppUserInfo.get("encryptedData");
    String iv = (String) wechatAppUserInfo.get("iv");

    WechatUserInfo wechatUserInfo = wechatAppManager.doOAuth(code, encryptedData, iv);
    if (wechatUserInfo == null) {
      throw new BusinessException(BusinessException.Code.WECHAT_OAUTH_ERROR, "微信小程序授权失败！！！");
    }
    HttpSession session = request.getSession(true);
    User user = wechatUserInfo.getUser();
    logger.debug("微信小程序用户 union id: {}, 对应车车用户{}", wechatUserInfo.getUnionid(), user.getId());
    session.setAttribute(WebConstants.SESSION_KEY_USER, CacheUtil.doJacksonSerialize(user));
    ClientTypeUtil.cacheClientType(request, ClientType.WE_CHAT_APP);
    return session.getId();
}

public static byte[] decrypt(String dataStr,String keyStr, String ivStr) throws Exception{
    Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());
    byte[] encryptedData = Base64.decode(dataStr);
    byte[] keyBytes = Base64.decode(keyStr);
    AlgorithmParameters iv = WechatAppDecryptor.generateIV(Base64.decode(ivStr));
    Key key = convertToKey(keyBytes);
    Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
    //设置为解密模式
    cipher.init(Cipher.DECRYPT_MODE, key,iv);
    return cipher.doFinal(encryptedData);
  }