JSONObject resultObject = JSONUtil.parseObj(body);

JSONObject resource = resultObject.getJSONObject("resource");

String cipherText = resource.getStr("ciphertext");

String nonceStr = resource.getStr("nonce");

String associatedData = resource.getStr("associated_data");

AesUtil aesUtil = new AesUtil(key.getBytes(StandardCharsets.UTF_8));

aesUtil.decryptToString(associatedData.getBytes(StandardCharsets.UTF_8), nonceStr.getBytes(StandardCharsets.UTF_8), cipherText);

每次到最后这一句这里，就报错 java.security.InvalidKeyException: Illegal key size，但是我完全是照搬的 https://pay.weixin.qq.com/wiki/doc/apiv3/wechatpay/wechatpay4_2.shtml 的解密函数啊，我验签这些也是成功的，支付也成功了。卡了两天了，要死了，求大伙儿帮帮俺