Twitter API状态更新总是返回“不正确的签名”

我在用 Signpost 作为OAuth实现,用于发布到Twitter。并实现了 GoogleAppEngineOAuthConsumer 和 GoogleAppEngineOAuthProvider 类,但由于它们很琐碎,所以我现在不提供它们的源代码。

这是我的身份验证部分,看起来工作得很好。

LoginServlet.java:

// fetching the request token
OAuthConsumer consumer = new GoogleAppEngineOAuthConsumer(CONSUMER_KEY, CONSUMER_SECRET);
OAuthProvider provider = new GoogleAppEngineOAuthProvider(REQUEST_TOKEN_URL, ACCESS_TOKEN_URL, AUTHORIZATION_URL);
String redirectUrl = provider.retrieveRequestToken(consumer, CALLBACK_URL);
// cache the request token and request token secret
response.sendRedirect(redirectUrl);

CallbackServlet.java

// fetching the access token
String verifier = (String) req.getParameter("oauth_verifier");
// retrieve request token and request token secret from cache
OAuthConsumer consumer = new GoogleAppEngineOAuthConsumer(CONSUMER_KEY, CONSUMER_SECRET);
OAuthProvider provider = new GoogleAppEngineOAuthProvider(REQUEST_TOKEN_URL, 
consumer.setTokenWithSecret(token, tokenSecret);
provider.setOAuth10a(true);
provider.retrieveAccessToken(consumer, verifier);
// store access token and access token secret

这是真正有问题的部分。

TweetServlet.java

OAuthConsumer consumer = new GoogleAppEngineOAuthConsumer(CONSUMER_KEY, CONSUMER_SECRET);
// retrieve access token and access token secret from storage
consumer.setTokenWithSecret(accessToken, accessTokenSecret);
final HTTPRequest updateStatus = new HTTPRequest(new URL("http://api.twitter.com/1/statuses/update.json"), HTTPMethod.POST);
updateStatus.setPayload(("status=" + URLEncoder.encode(message, "UTF-8")).getBytes());
consumer.sign(updateStatus);
logger.debug(new String(URLFetchServiceFactory.getURLFetchService().fetch(updateStatus).getContent()));

每次结果: {"request":"/1/statuses/update.json","error":"Incorrect signature"} .