Retrofit fetch authorization token based on specific error message using RxAndroid

Question

I have a bunch of retrofit observables that require authorization token in the header for every request. Token has an expiry time of an hour.

@GET("objects/abc")
    Observable<List<Object>> apiCustomView(@Query("isMobileViews") boolean isMobileViews);

This is my Retrofit service class where authorization token is provided for each request.

class Factory {
        public static RetrofitService create() {
            Interceptor interceptor = chain -> {
                Request newRequest = chain.request().newBuilder().addHeader("Authorization",
                        "Bearer "+ Util.getSharedPref("token")).build();
                return chain.proceed(newRequest);
            };

            OkHttpClient.Builder builder = new OkHttpClient.Builder();
            builder.interceptors().add(interceptor);
            OkHttpClient client = builder.build();

            Retrofit retrofit = new Retrofit.Builder()
                    .baseUrl("http://url.com/api/")
                    .client(client)
                    .addConverterFactory(GsonConverterFactory.create())
                    .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
                    .build();
            return retrofit.create(RetrofitService.class);
        }
    }

Here is consuming the service to get the data -

retrofitService.apiCustomView(isMobileViews)
   .observeOn(AndroidSchedulers.mainThread())
   .subscribeOn(application.defaultSubscribeScheduler())
   .subscribe(new Subscriber < List < Object >> () {
    @Override
    public void onCompleted() {
     if (!mObjects.isEmpty()) {
      // Add to database and present data
     }
    }

    @Override
    public void onError(Throwable error) {
     // Present Data from Database
    }

    @Override
    public void onNext(List < Object > objectList) {
    mObjects = objectList;
    }
 });

I want to modify the request in such a way that whenever I receive authorization failed error, I will fetch the authorization token and resume the same request. On any other type of error, I want to show saved data.

Jahnold Jahnold · Accepted Answer · 2016-06-02T13:03:36

You can access the network response from Retrofit by changing the return type of your Observable:

@GET("objects/abc")
Observable<Response<List<Object>>> apiCustomView(@Query("isMobileViews") boolean isMobileViews);

Then you can check the error type in a flatmap:

retrofitService.apiCustomView(isMobileViews)
   .flatMap(new Func1<Response<List<Object>>, Observable<List<Object>() {
        @Override
        public Observable<List<Object>> call(Response<List<Object>> response) {

            if (response.isSuccess()) {
                return Observable.just(response.body());
            }
            else if (response.code() == 403) {
                // get new auth token and try again
                return getNewAuthKeyAndTryAgain();
            }
            else {
                return Observable.error(/* create an exception*/)
            }
        }
   })
   .subscribeOn(application.defaultSubscribeScheduler())
   .observeOn(AndroidSchedulers.mainThread())
   .subscribe(...);

To get the new auth token and run the request again I would create a function which does this:

private Observable<List<Object>> getNewAuthKeyAndTryAgain() {

    return retrofitService
                .getNewKey()
                .flatMap(new Func1<String, Observable<Response<List<Object>>>>() {
                    @Override
                    public Observable<Response<List<Object>>> call(String s) {

                        // save key where you need to
                        return retrofitService.apiCustomView(isMobileViews);
                    }
                })
                .flatMap(new Func1<Response<List<Object>>, Observable<List<Object>>>() {
                    @Override
                    public Observable<List<Object>> call(Response<List<Object> response) {
                        return response.body();
                    }
                });
}

Retrofit fetch authorization token based on specific error message using RxAndroid

2 Answers