How to get Facebook Rate Limit Header using Facebook4J?

Question

According to Facebook Docs

If your app is making enough calls to be considered for rate limiting by our system, we return an X-App-Usage HTTP header. [...] When any of these metrics exceed 100 the app will be rate limited.

I am using Facebook4J to connect my application to the Facebook API. But I could not find any documentation about how I can get the X-App-Usage HTTP header after a Facebook call, in order to avoid being rate limited. I want to use this header to know dinamically if I need to increase or decrease the time between each API call.

So, my question is: using Facebook4J, is possible to check if Facebook returned the X-App-Usage HTTP header and get it? How?

Answer 1

There is a getResponseHeader method for the response of BatchRequests in facebook4j see Facebook4j code examples

You could try getResponseHeader("X-App-Usage")

// Executing "me" and "me/friends?limit=50" endpoints
BatchRequests<BatchRequest> batch = new BatchRequests<BatchRequest>();
batch.add(new BatchRequest(RequestMethod.GET, "me"));
batch.add(new BatchRequest(RequestMethod.GET, "me/friends?limit=50"));
List<BatchResponse> results = facebook.executeBatch(batch);

BatchResponse result1 = results.get(0);
BatchResponse result2 = results.get(1);

// You can get http status code or headers
int statusCode1 = result1.getStatusCode();
String contentType = result1.getResponseHeader("Content-Type");

// You can get body content via as****() method
String jsonString = result1.asString();
JSONObject jsonObject = result1.asJSONObject();
ResponseList<JSONObject> responseList = result2.asResponseList();

// You can map json to java object using DataObjectFactory#create****()
User user = DataObjectFactory.createUser(jsonString);
Friend friend1 = DataObjectFactory.createFriend(responseList.get(0).toString());
Friend friend2 = DataObjectFactory.createFriend(responseList.get(1).toString());