Twitter oauth Request Token Response code 401

I am working on a twitter oauth login. However, when I do the request_token, the very first step, the response code always return 401 Unauthorized.

I have searched a lot for a week, but I cannot find the solution, please help.

Here is my connection:

URL url = new URL("https://api.twitter.com/oauth/request_token");
HttpURLConnection conn = (HttpURLConnection)url.openConnection();
conn.setRequestProperty("Host","api.twitter.com");
conn.setRequestProperty("Authorization", data);
conn.setRequestMethod("POST");
conn.connect();

For my data:

String data = "OAuth oauth_nonce=\"" + oa开发者_运维知识库uth_nonce
    + "\", oauth_callback=\"" + oauth_callback
    + "\", oauth_signature_method=\"" + oauth_signature_method
    + "\", oauth_timestamp=\"" + oauth_timestamp
    + "\", oauth_consumer_key=\"" + oauth_consumer_key
    + "\", oauth_signature=\"" + oauth_signature
    + "\", oauth_version=\"" + oauth_version + "\"";  

Also, I am sure that my signature is right, because I used the parameter of twitter example, I can calculate the same result as its example, so I think my method is right.

Here is my calculation:

String oauth_para = "oauth_callback=" + oauth_callback
    + "&oauth_consumer_key=" + oauth_consumer_key
    + "&oauth_nonce=" + oauth_nonce
    + "&oauth_signature_method=" + oauth_signature_method
    + "&oauth_timestamp=" + oauth_timestamp
    + "&oauth_version=" + oauth_version;

String signingRequests = "POST&" + requestToken + "&" + URLEncoder.encode(oauth_para, "UTF-8");

String key = oauth_consumer_secret + "&";
SecretKeySpec signingKey = new SecretKeySpec(key.getBytes(), "HmacSHA1");

Mac mac = null;
try {
    mac = Mac.getInstance("HmacSHA1");
    mac.init(signingKey);
}
catch(Exception e) {
    System.err.println("Error: " + e);
}
byte[] rawHmac = mac.doFinal(signingRequests.getBytes());

String oauth_signature =  Base64.encodeBytes(rawHmac);
oauth_signature = URLEncoder.encode(oauth_signature);

I understand that the nonce and timestamp should be random and unique. So, my method is like that:

StringBuffer buffer = new StringBuffer("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"); 
StringBuffer sb = new StringBuffer(); 
Random r = new Random(); 
int range = buffer.length(); 
for (int i = 0; i < 43;i ++) { 
    sb.append(buffer.charAt(r.nextInt(range))); 
} 
long epoch = System.currentTimeMillis() / 1000;
String oauth_nonce = sb.toString();

Can somebody help me?

P.S: I have also removed my apps, and then create a new one. The result also is the same. Also, the apps is write and read already.

hey,,, I was getting the same problem 1 min ago, but I figured this out. My problem, at least, was that in the configuration of the application(inside twitter), my application type was Client, when should be Browser! So I changed to Browser, put a callback URL and worked fine!!