String getSignature(URL url, Invocation invocation, String secretKey, String time) {
        String requestString = String.format(
                Constants.SIGNATURE_STRING_FORMAT,
                url.getColonSeparatedKey(),
                RpcUtils.getMethodName(invocation),
                secretKey,
                time);
        boolean parameterEncrypt = url.getParameter(Constants.PARAMETER_SIGNATURE_ENABLE_KEY, false);
        if (parameterEncrypt) {
            return SignatureUtils.sign(invocation.getArguments(), requestString, secretKey);
        }
        return SignatureUtils.sign(requestString, secretKey);
    }
@Test
    void testGetSignatureNoParameter() {
        URL url = mock(URL.class);
        Invocation invocation = mock(Invocation.class);
        String secretKey = "123456";
        AccessKeyAuthenticator helper = new AccessKeyAuthenticator(ApplicationModel.defaultModel());
        String signature = helper.getSignature(url, invocation, secretKey, String.valueOf(System.currentTimeMillis()));
        assertNotNull(signature);
    }