Why does the Facebook Graph API respond with the same "next" URL over and over? - facebook

Question

I am using Volley to submit POST requests to the Facebook Graph API in order to retrieve information about photos and videos from a user account using their BATCH facility so I get it all in one go (rather than making one call for photos, one for videos). The first call works perfectly:
request = new StringRequest(Request.Method.POST,
"https://graph.facebook.com",
future,
new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
Timber.e("Got VolleyError: %s", error.getMessage());
}
}) {
#Override
public String getBodyContentType() {
return "application/x-www-form-urlencoded; charset=" + getParamsEncoding();
}
#Override
protected Map<String, String> getParams() throws AuthFailureError {
Map<String,String> params = new HashMap<>();
JSONArray batchRequest = new JSONArray();
JSONObject photoRequest = new JSONObject();
JSONObject videoRequest = new JSONObject();
try {
photoRequest.put("method", "GET");
photoRequest.put("relative_url",facebookUserID + String.format("?fields=photos.limit(%1$s){id,created_time,images{source},picture}",batchSize));
videoRequest.put("method", "GET");
videoRequest.put("relative_url",facebookUserID + String.format("?fields=videos.limit(%1$s){id,created_time,source,picture}",batchSize));
batchRequest.put(photoRequest);
batchRequest.put(videoRequest);
} catch (JSONException e) {
Timber.d("Lifecycle: Exception constructing batch request: %s", e.getMessage());
return null;
}
//try {
// Timber.d("Lifecycle: batchRequest: %s", batchRequest.toString(2));
//} catch (JSONException e) {
// e.printStackTrace();
//}
params.put("batch", batchRequest.toString());
params.put("include_headers", "false");
params.put(FB_BASE_ACCESSTOKEN_KEY, facebookToken);
return params;
}
};
InTouchUtils.addToRequestQueue(request);
// Using a blocking volley request, this chain has been called on a separate async task
// See SO: https://stackoverflow.com/questions/16904741/can-i-do-a-synchronous-request-with-volley
facebookRetval = future.get(VOLLEY_REQUEST_DEFAULT_TIMEOUT, TimeUnit.SECONDS);
returnResult = parseBatchRequest(facebookRetval);
The returned JSON has all the fields I've requested, as well as the pagination block with cursors, and a "next" and/or "previous" url, per the Facebook documentation.
A "next" URL looks something like:
https://graph.facebook.com/v7.0/FACEBOOK_ID_HERE/photos?access_token=ACCESS_TOKEN_HERE&fields=id,created_time,images{source},picture&limit=5&after=AFTER_TOKEN_HERE
There is one of these that gets passed back from the batch operation for each of the original GET operations (assuming both photos and videos have greater than LIMIT items).
Again, this part works fine.
But when I try and use that "next" URL to create another BATCH call, it fails with an "unsupported GET operation" error. This is true even though I can use a standard Volley GET using that exact same URL and it works perfectly.
I have tried using the "https://graph.facebook.com" portion of the above URL as the root of the POST (like what worked in the initial call), and everything after that as the "relative_url" parameter. No go.
Then I tried parsing out just the "after" portion of the "next" url, and constructing a new relative_url that was exactly like the first one, but tacking on a "&after=" + AFTER_VALUE to it as the relative_url. No go - in fact, while this succeeded in making the call, I keep getting the initial batch over and over and over. It is like it is ignoring the "&after=" parameter.
For now I am back to making two GET calls (one for photos, one for videos) just using the NEXT url as long as it keeps being passed back to me. This works fine, but obviously I'm making two network calls instead of the single batch one.
Ideas?

Answer 1

A little more examination revealed that I had made a string parsing error on the subsequent batch operation, and was inadvertently including a forward slash when I should not have been.
For those new to using the batch API, the lesson is that you need "https://graph.facebook.com" as the POST url (no trailing forward slash), then your relative url should NOT start with a forward slash. So the URL I was trying to utilize on calls 2..N like this:
https://graph.facebook.com/v7.0/FACEBOOK_ID_HERE/photos?access_token=ACCESS_TOKEN_HERE&fields=id,created_time,images{source},picture&limit=5&after=AFTER_TOKEN_HERE
should be broken out as:
photoRequest.put("relative_url", "v7.0/FACEBOOK_ID_HERE/photos?access_token=ACCESS_TOKEN_HERE&fields=id,created_time,images{source},picture&limit=5&after=AFTER_TOKEN_HERE");
The API handles putting in the forward slash between the root and the relative url.