Repeat Network API call if some condition is true using RXjava

Question

I am new In RX-JAVA, Now I am facing one problem I just want to repeat one method till certain condition is not true. I am using Retrofit for network call. I'll hit one Google Calendar API, from this API response I'll get one token if That token value is not empty or Non null than I need to use this token to call the same API with this token.

public void getGoogleCalenderEvents(String auth, String calenderId, String token) {
        auth = AUTH_HEADER_PREFIX + auth;
        String orderBy = "updated";
        Pair<Calendar, Calendar> pair = getCalendarStartAndEndTime();
        String finalAuth = auth;
        mCalenderApiRequest.getAllEvent(auth, calenderId, pair.first, pair.second, orderBy)
                .map(response -> {
                    FileLogUtils.d(TAG, "getGoogleCalenderEvents():: deleting the previous data and storing into DB: response:" + response);
                    EventsRepository.getInstance().deleteAllData();
                    EventsRepository.getInstance().insert(response.toString());
                    return response;
                }).subscribe(response-> {
                    if (TextUtils.isEmpty(response.getToken)){
                        getGoogleCalenderEvents(finalAuth, calenderId,response.getToken());
                    } else {
                        // Nothing ToDo
                    }
        }, ErrorHandler::logError);
    }

Answer 1

In order to have a proper code I need to know the signature of mCalenderApiRequest.getAllEvent. For the code below I'm assuming it returns a Single:

       mCalenderApiRequest.getAllEvent(auth, calenderId, pair.first, pair.second, orderBy)
                // same as your original code but with doOnSuccess instead of flatMap
                .doOnSuccess(response -> {
                    FileLogUtils.d(TAG, "getGoogleCalenderEvents():: deleting the previous data and storing into DB: response:" + response);
                    EventsRepository.getInstance().deleteAllData();
                    EventsRepository.getInstance().insert(response.toString());
                })
                // check if response has empty token and throw EmptyTokenException
                .flatMap(response -> {
                    if (response.getToken().isEmpty()) {
                        return Single.error(new EmptyTokenException());
                    } else {
                        return Single.just(response);
                    }
                })
                // check if error thrown is EmptyTokenException and retry
                .retryWhen(errors -> errors.flatMap(error -> {
                            if (error instanceof EmptyTokenException) {
                                // the value returned is irrelevant
                                return Flowable.just("retry me!");
                            }

                            // don't retry if error thrown is different than EmptyTokenException
                            return Flowable.error(error);
                        }
                ))
                .subscribe(response -> {
                    // nothing to do
                }, ErrorHandler::logError);

and create this auxiliary class:

class EmptyTokenException extends Exception {}