将POST请求发送到https://accounts.google.com/o/oauth2/token时出现400错误

Question

我正在尝试实现Google Play开发者API，以便从服务器端获取我的用户的所有IAP和订阅详细信息（到期，用户退款等）。

我遵循了https://developers.google.com/android-publisher/authorization的指南和Am I getting the steps right for verifying a user's Android in-app subscription?的步骤，直到我必须向https://accounts.google.com/o/oauth2/token url发送POST请求为止。

我尝试根据https://webdevdesigner.com/q/invalid-grant-trying-to-get-oauth-token-from-google-6945/上的用户，用我的服务帐户电子邮件（app-name@api-1234-56789.iam.gserviceaccount.com）替换客户端ID，以重新启动整个步骤。他说Google文档对客户ID产生误导。这给了我“错误400：redirect_uri_mismatch”，并且没有选择将重定向uri添加到Google Cloud控制台上的服务帐户的选项。 然后，我尝试在https://reqbin.com/上发送请求，但得到的响应与下面的Java源代码相同。

I/System.out: Resp Code: 400
    Resp Message:Bad Request
I/System.out: {
      "error": "invalid_grant",
      "error_description": "Bad Request"

    private void testOAuth()
    {
        try
        {
            String query = "client_id="+URLEncoder.encode("***-***.apps.googleusercontent.com","UTF-8");
            query += "&";
            query += "client_secret="+ URLEncoder.encode("***-***","UTF-8") ;
            query += "&";
            query += "code="+ URLEncoder.encode("4/***","UTF-8") ;
            query += "&";
            query += "grant_type="+ URLEncoder.encode("authorization_code","UTF-8") ;
            query += "&";
            query += "redirect_uri="+ URLEncoder.encode("https://www.google.com","UTF-8") ;
            /*query += "&";
            query += "scope="+ URLEncoder.encode("https://www.googleapis.com/auth/androidpublisher","UTF-8") ;*/

            URL url=new URL("https://accounts.google.com/o/oauth2/token");
            HttpsURLConnection httpsURLConnection=(HttpsURLConnection) url.openConnection();
            httpsURLConnection.setRequestMethod("POST");


            httpsURLConnection.setRequestProperty("Content-length", String.valueOf(query.length()));
            httpsURLConnection.setRequestProperty("Content-Type","application/json");
            //httpsURLConnection.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0;Windows98;DigExt)");
            //httpsURLConnection.setDoInput(true);
            httpsURLConnection.setDoOutput(true);
            httpsURLConnection.setInstanceFollowRedirects(true);

            DataOutputStream dataOutputStream = new DataOutputStream(httpsURLConnection.getOutputStream());
            dataOutputStream.writeBytes(query);
            dataOutputStream.close();

            /*DataInputStream dataInputStream=new DataInputStream(httpsURLConnection.getInputStream());
            for( int c = dataInputStream.read(); c != -1; c = dataInputStream.read() ){System.out.print( (char)c );}
            dataInputStream.close();*/

            int responseCode=httpsURLConnection.getResponseCode();
            System.out.println("Resp Code: "+responseCode);
            System.out.println("Resp Message:"+ httpsURLConnection.getResponseMessage());
            if(responseCode>=400)
            {
                DataInputStream errorStream=new DataInputStream(httpsURLConnection.getErrorStream());
                for( int c = errorStream.read(); c != -1; c = errorStream.read() ){System.out.print( (char)c );}
                errorStream.close();
            }
        }
        catch(MalformedURLException e){e.printStackTrace();}
        catch (IOException e){e.printStackTrace();}
        }
        catch(MalformedURLException e){e.printStackTrace();}
        catch (IOException e){e.printStackTrace();}
    }