验证回调请求

Dabank 发起回调时，你的服务器端需要对回调参数签名进行验证

Map<String, String> m = parseRequest(); //将请求解析为map

String ret = DabankClient.verifyCallbackDataWithPublicKey(m, "your_app_public_key__downloaded_from_dabank_open_platform");
assertNull(ret);