Android Retrofit POST request cache

Question

Which is best way to store retrofit POST request cache ?

I will store response and using that response while user is offline. I was referred this link.
1) Can Retrofit with OKHttp use cache data when offline
2) Cache POST requests with OkHttp

But in this link cache mechanism work only GET method.
- It is possible to store cache in post request using retrofit ?
- Is any library to handle network cache?

Thanks

possible or not, POST requests are meant to change data in the server, are you sure you want to cache them? — lelloman, Aug 19 '16 at 14:15
Hello @lelloman in my case I will get response from cache while user is offline — Mitesh Vanaliya, Aug 20 '16 at 06:01

score 2 · Accepted Answer · answered Aug 19 '16 at 13:53

2

OkHttp have support for file cache

answered Aug 19 '16 at 13:53

Alex Shutov

3,217
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4

OKHttp does NOT support caching of POST requests, only GET – galaxigirl Oct 04 '17 at 07:31

score 0 · Answer 2 · answered Dec 08 '17 at 06:06

This is the solution we ended up with

public class OnErrorRetryCache<T> {

    public static <T> Observable<T> from(Observable<T> source) {
         return new OnErrorRetryCache<>(source).deferred;
    }

    private final Observable<T> deferred;
    private final Semaphore singlePermit = new Semaphore(1);

    private Observable<T> cache = null;
    private Observable<T> inProgress = null;

    private OnErrorRetryCache(Observable<T> source) {
        deferred = Observable.defer(() -> createWhenObserverSubscribes(source));
    }

    private Observable<T> createWhenObserverSubscribes(Observable<T> source) 
    {
        singlePermit.acquireUninterruptibly();

        Observable<T> cached = cache;
        if (cached != null) {
            singlePermit.release();
            return cached;
        }

        inProgress = source
                .doOnCompleted(this::onSuccess)
                .doOnTerminate(this::onTermination)
                .replay()
                .autoConnect();

        return inProgress;
    }

    private void onSuccess() {
        cache = inProgress;
    }

    private void onTermination() {
        inProgress = null;
        singlePermit.release();
    }
}

We needed to cache the result of an HTTP request from Retrofit. So this was created, with an observable that emits a single item in mind.

If an observer subscribed while the HTTP request was being executed, we wanted it to wait and not execute the request twice, unless the in-progress one failed. To do that the semaphore allows single access to the block that creates or returns the cached observable, and if a new observable is created, we wait until that one terminates.

Android Retrofit POST request cache

2 Answers2