访问Google oAuth给出无效的grant_type(错误的请求)

Question

我在SO中搜索了很多，浏览了许多关于相同错误的问题，应用了他们提出的任何建议，但没有任何结果。

我正在学习如何调用谷歌API(说谷歌日历API)。我正在通过谷歌开发人员教程从https://developers.google.com/identity/protocols/OAuth2ServiceAccount

所以我在google中创建了一个服务帐户，创建了凭据(我想从我自己的应用程序调用google API)。然后，我创建JWT，用google共享的私钥签名JWT，并进行REST POST调用以获得oAuth。这是我的代码

public class TestGoogleAPI {
public static void main(String[] args) throws Exception{
    String header = "{"alg":"RS256","typ":"JWT"}";
    long time = Calendar.getInstance().getTimeInMillis()/1000;
    String claimSet = "{"iss":"xxxxxxxxxxxxxxxxxxxxxxxxxxxx.apps.googleusercontent.com"," +
                ""scope":"https://www.googleapis.com/auth/calendar"," +
                ""aud":"https://www.googleapis.com/oauth2/v3/token"," +
                ""exp":"+ (time+3600) +"," +
                ""iat":" + time +"}";

    String base64Header = new String(Base64.encodeBase64(header.getBytes()),"UTF-8");
    String base64ClaimSet = new String(Base64.encodeBase64(claimSet.getBytes()),"UTF-8");
    String input = base64Header + "." + base64ClaimSet;
    File f = new File("D:/downloads/privatekey.txt");
    FileInputStream fis = new FileInputStream(f);
    DataInputStream dis = new DataInputStream(fis);
    byte[] keyBytes = new byte[(int)f.length()];
    dis.readFully(keyBytes);
    dis.close();
    byte[] key = Base64.decodeBase64(keyBytes);
    PKCS8EncodedKeySpec spec = new PKCS8EncodedKeySpec(key);
    KeyFactory kf = KeyFactory.getInstance("RSA");
    PrivateKey privatekey =  kf.generatePrivate(spec);
    Signature signature = Signature.getInstance("SHA256withRSA"); 
    signature.initSign(privatekey);
    signature.update(input.getBytes());
    String base64Sign = new String(Base64.encodeBase64(signature.sign()),"UTF-8");
    doHttpPost("https://www.googleapis.com/oauth2/v3/token", input + "." + base64Sign);
}
public static void doHttpPost(String urlStr, String assertion) throws Exception{
    URL url = new URL(urlStr);
      HttpURLConnection conn = (HttpURLConnection) url.openConnection();
      conn.setRequestMethod("POST");
      conn.setDoOutput(true);
      conn.setDoInput(true);
      conn.setUseCaches(false);
      conn.setAllowUserInteraction(false);
      conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
      OutputStream out = conn.getOutputStream();
      Writer writer = new OutputStreamWriter(out, "UTF-8");
      writer.write("grant_type");
      writer.write("=");
      writer.write(URLEncoder.encode("urn:ietf:params:oauth:grant-type:jwt-bearer", "UTF-8"));
      writer.write("&");
      writer.write("assertion");
      writer.write("=");
      writer.write(URLEncoder.encode(assertion, "UTF-8"));
      writer.close();
      out.close();
      if (conn.getResponseCode() != 200) {
          System.out.println(conn.getResponseMessage());
      }
      BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream()));
      StringBuilder sb = new StringBuilder();
      String line;
      while ((line = rd.readLine()) != null) {
        sb.append(line);
      }
      rd.close();
      conn.disconnect();
      System.out.println(sb.toString());
}
}

我收到了400(错误的请求)。我尝试了同样的"Chrome的高级休息客户端"，但结果是一样的，无效的grant_type(坏请求)。

{
   error: "invalid_grant"
   error_description: "Bad Request"
}

我在这里错过了什么吗?请帮帮我

谢谢

Answer 1

最后我得到了分辨率。当我编码头和声明集时，我正在做base64编码，而不是base64safeURL编码。更换

后

Base64.encodeBase64(some_data);

Base64.encodeBase64URLSafe(some_data);

在上述代码中出现时，一切正常。我正在获得访问令牌，并能够击中谷歌API与oAuth令牌