Получить токен доступа из Azure AD Java

Я хочу получить ответ Azure RateCard Json через Billing REST API. Для этого я использую следующий код в eclipse:

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonToken;

public class RateCardRest {

public static String getAccessToken(String tenantId, String clientId, String clientSecret)
        throws MalformedURLException, IOException {
    String endpoint = String.format("https://login.microsoftonline.com/%s/oauth2/token", tenantId);
    String postBody = String.format("grant_type=client_credentials&client_id=%s&client_secret=%s&resource=%s",
            clientId, clientSecret, "https://management.azure.com/");
    HttpURLConnection conn = (HttpURLConnection) new URL(endpoint).openConnection();
    conn.setRequestMethod("POST");
    conn.addRequestProperty("Content-Type", "application/x-www-form-urlencoded");
    conn.setDoOutput(true);
    conn.getOutputStream().write(postBody.getBytes());
    conn.connect();
//      If you want to see the response content, please use the commented code below.
//      BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
//      StringBuilder builder = new StringBuilder();
//      String line = null;
//      while ((line = reader.readLine()) != null) {
//          builder.append(line);
//      }
//      reader.close();
//      System.out.println(builder.toString());
//      The output for access token is {"token_type":"Bearer","expires_in":"3600","ext_expires_in":"3600","expires_on":"1550660092","not_before":"1550656192","resource":"https://management.azure.com/","access_token":"eyJ0eXAiOiJKV1QiL...."}
    JsonFactory factory = new JsonFactory();
    JsonParser parser = factory.createParser(conn.getInputStream());
    String accessToken = null;
    while (parser.nextToken() != JsonToken.END_OBJECT) {
        String name = parser.getCurrentName();
        if ("access_token".equals(name)) {
            parser.nextToken();
            accessToken = parser.getText();
        }
    }
    return accessToken;
}

public static String getRateCard(String subscriptionId, String apiVersion, String offerId, String currency,
        String locale, String region, String accessToken) throws MalformedURLException, IOException {
    String endpoint = String.format(
            "https://management.azure.com/subscriptions/%s/providers/Microsoft.Commerce/RateCard?api-version=%s&$filter=OfferDurableId eq '%s' and Currency eq '%s' and Locale eq '%s' and RegionInfo eq '%s'",
            subscriptionId, apiVersion, offerId, currency, locale, region).replaceAll(" ", "%20");
    HttpURLConnection conn = (HttpURLConnection) new URL(endpoint).openConnection();
    conn.setRequestMethod("GET");
    conn.addRequestProperty("Authorization", "Bearer " + accessToken);
    conn.addRequestProperty("Content-Type", "application/json");
    conn.connect();
    BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
    StringBuilder builder = new StringBuilder();
    String line = null;
    while ((line = reader.readLine()) != null) {
        builder.append(line);
    }
    reader.close();
    return builder.toString();
}

public static void main(String[] args) throws MalformedURLException, IOException {
    String tenantId = "<your tenant id like xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxxx";
    String clientId = "<your client id registed in AAD like xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxxx";
    String clientSecret = "<your client secret key generated in AAD>";
    String accessToken = getAccessToken(tenantId, clientId, clientSecret);
    System.out.println(accessToken);
    String subscriptionId = "<your subscription id like xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxxx";
    String apiVersion = "2015-06-01-preview";
    String offerId = "<your offer id like XX-AZR-XXXXX";
    String currency = "USD";
    String locale = "en-US";
    String region = "US";
    String rateCardResp = getRateCard(subscriptionId, apiVersion, offerId, currency, locale, region, accessToken);
    System.out.println(rateCardResp);
}

 }

Это вызывает следующую ошибку:

Exception in thread "main" java.io.IOException: Server returned HTTP response code: 401 for URL: https://login.microsoftonline.com/"myTenantID"/oauth2/token
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(Unknown Source)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
    at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(Unknown Source)
    at com.nttdata.altemista.RateCardRest.getAccessToken(RateCardRest.java:38)
    at com.nttdata.altemista.RateCardRest.main(RateCardRest.java:74)

Когда я ищу URL-адрес, я получаю следующее сообщение:

AADSTS900561: The endpoint only accepts POST, OPTIONS requests. Received a GET request.