Youtube Analytics & Google Service Account

Objectives:Implement a program (java or python) to retrieve data from videos that I published on my Youtube channel. This program will be launched daily (1:00 AM).

Solutions:To retrieve data Youtube, including the number of views per day, YouTube Analytics API is in my opinion the best solution. I use the Google Account Service ("GoogleCredential") to authenticate me:

static {    // Build service account credential.    try {        // Create a listener for automatic refresh OAuthAccessToken        List<CredentialRefreshListener> list = new ArrayList<CredentialRefreshListener>();        list.add(new CredentialRefreshListener() {            public void onTokenResponse(Credential credential,                    TokenResponse tokenResponse) throws IOException {                System.out.println(tokenResponse.toPrettyString());            }            public void onTokenErrorResponse(Credential credential,                    TokenErrorResponse tokenErrorResponse)                    throws IOException {                System.err.println("Error: "+ tokenErrorResponse.toPrettyString());            }        });        // Create a GoogleCredential for authenticate with ServiceAccount        // service        credential = new GoogleCredential.Builder()                .setTransport(HTTP_TRANSPORT)                .setJsonFactory(JSON_FACTORY)                .setServiceAccountId(SERVICE_ACCOUNT_EMAIL)                .setServiceAccountScopes(SCOPES)                .setClock(Clock.SYSTEM)                .setServiceAccountPrivateKeyFromP12File(                        new File("key.p12"))                .setRefreshListeners(list).build();        credential.refreshToken();    } catch (GeneralSecurityException e) {        e.printStackTrace();    } catch (IOException e) {        e.printStackTrace();    }}

And I execute Youtube Analytics query:

YoutubeAnalytics youtubeAnalytics = new YoutubeAnalytics.Builder(HTTP_TRANSPORT, JSON_FACTORY, credential)        .setApplicationName("Test-YouTube-Analytics/1.0").build();    // Create request    credential.refreshToken();    YoutubeAnalyticsRequest<?> request = youtubeAnalytics.reports()            .query("channel=="+ channelId, "2012-10-01", "2012-12-01", "views")            .setAlt("json")            .setKey(API_KEY)            .setDimensions("month")            .setPrettyPrint(true);    System.out.println(request.buildHttpRequest().getUrl().toString());    ResultTable first = (ResultTable) request.execute();}

But I get the following error:

com.google.api.client.googleapis.json.GoogleJsonResponseException: 500 Internal Server Error{"code" : 500,"errors" : [ {"domain" : "global","message" : "Unknown error occurred on the server.","reason" : "internalError"  } ],"message" : "Unknown error occurred on the server."}

Thanks for your insight!