RxJava-等待其他活动/片段中的其他可观察对象的retryWhen完成

Question

用例：我正在开发一个Android应用程序，它有一个带有4个选项卡的视图页码，所有这些选项卡都是片段。对于每个选项卡/片段，我必须连接到具有 Oauth 的 REST Api，并且令牌每 5 分钟过期一次。

当前解决方案：使用RxJava和retryWhen操作符，我可以在收到401 HTTP错误时重新进行身份验证。对于订阅和消费的每个可观察流，使用：

retryWhen(refreshTokenAuthenticator)

因此，当令牌到期时，流将使用它，然后执行真正的api调用。

问题：这仅适用于一个订阅中使用的一个可观察量，但我需要允许用户在不阻止他/她的情况下在选项卡之间切换，同时考虑到401错误可能随时出现在任何API调用的任何片段中。

问题：有没有一种方法可以让可观察对象等待其他可观察对象使用不在同一流/订阅者中的onNext（）完成？事实上在不同的Fragments中？所以api调用场景将如下所示：

Api Call Fragment A --> request
Api Call Fragment A <-- response 200 Code

Api Call Fragment B --> request
Api Call Fragment B <-- response 401 Code (retryWhen in action)
Api Call Fragment B --> request (refreshToken)
Api Call Fragment B <-- response 200 (with new access token saved in the app)

几乎在同一时间...

Api Call Fragment C --> request
Api Call Fragment C <-- response 401 Code (retryWhen in action)

Observable in Fragment C Waits till Observable in Fragment B finish (onNext())

Api Call Fragment C --> request
Api Call Fragment C <-- response 200

这是我已经拥有的，每个API调用看起来几乎相同：

public void getDashboardDetail() {

    Subscription subscription = repository.getDashboard()
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())
            .retryWhen(tokenAuthenticator)
            .subscribe(new RestHttpObserver<UserDataDto>() {
                @Override
                public void onUnknownError(Throwable e) {
                    getMvpView().onError(e);
                }

                @Override
                public void onHostUnreachable() {
                    getMvpView().onHostUnreachable();
                }

                @Override
                public void onHttpErrorCode(int errorCode, ErrorDto errorDto) {
                    getMvpView().onHttpErrorCode(errorCode, errorDto);
                }

                @Override
                public void onCompleted() {
                    //Do nothing...
                }

                @Override
                public void onNext(UserDataDto response) {
                    getMvpView().onReceiveUserData(response);
                }
            });

    this.compositeSubscription.add(subscription);

}

和我的RefreshTokenAuthenticator：

public class RefreshTokenAuthenticator implements Func1<Observable<? extends Throwable>, Observable<?>> {

private static final int RETRY_COUNT = 1;

private static final int HTTP_ERROR_CODE = 401;

@Inject
private UserRepository repository;

@Inject
private SessionManager sessionManager;

@Inject
private MyApplication application;


@Inject
private RefreshTokenAuthenticator() {
}

@Override
public synchronized Observable<?> call(Observable<? extends Throwable> observable) {
    return observable
            .flatMap(new Func1<Throwable, Observable<?>>() {
                int retryCount = 0;

                @Override
                public Observable<?> call(final Throwable throwable) {

                    retryCount++;
                    if (retryCount <= RETRY_COUNT && throwable instanceof HttpException) {
                        int errorCode = ((HttpException) throwable).code();
                        if (errorCode == HTTP_ERROR_CODE) {
                            return repository
                                    .refreshToken(sessionManager.getAuthToken().getRefreshToken())
                                    .observeOn(AndroidSchedulers.mainThread())
                                    .subscribeOn(Schedulers.io())

                                    .doOnNext(tokenDto -> sessionManager.saveAuthToken(tokenDto))
                                    .doOnError(throwable1 -> {
                                        Log.e("RefreshTokenAuth", "DoOnError", throwable1);
                                        application.logout();
                                    });

                        }
                    }
                    // No more retries. Pass the original Retrofit error through.
                    return Observable.error(throwable);
                }
            });
}

}

Answer 1

最后，只需添加一个全局（在我的应用程序类中）布尔值（如果应用当前是否重新进行身份验证），即可使其正常工作。它实际上允许两个401 HTTP错误，但第二个错误继续在onNext（）中并重新执行初始可观察量。我想做一些更被动的事情，但至少这解决了我的主要问题。

public class RefreshTokenAuthenticator implements Func1<Observable<? extends Throwable>, Observable<?>> {

private static final int RETRY_COUNT = 1;

private static final int HTTP_ERROR_CODE = 401;

@Inject
private UserRepository repository;

@Inject
private SessionManager sessionManager;

@Inject
private MyApplication application;


@Inject
private RefreshTokenAuthenticator() {
}

@Override
public Observable<?> call(Observable<? extends Throwable> observable) {
    return observable
            .flatMap(new Func1<Throwable, Observable<?>>() {
                int retryCount = 0;

                @Override
                public Observable<?> call(final Throwable throwable) {

                    retryCount++;
                    if (retryCount <= RETRY_COUNT && throwable instanceof HttpException) {
                        int errorCode = ((HttpException) throwable).code();

                        if (errorCode == HTTP_ERROR_CODE) {

                            Log.i("RefreshTokenAuth", "APPLICATION IS AUTHENTICATING = " + application.isAuthenticating);
                            if (!application.isAuthenticating) {
                                application.isAuthenticating = true;

                                String refreshToken = sessionManager.getAuthToken().getRefreshToken();

                                return repository
                                        .refreshToken(refreshToken)
                                        .observeOn(AndroidSchedulers.mainThread())
                                        .subscribeOn(Schedulers.io())
                                        .doOnCompleted(() -> application.isAuthenticating = false)
                                        .doOnNext(tokenDto -> sessionManager.saveAuthToken(tokenDto))
                                        .doOnError(throwable1 -> {
                                            Log.e("RefreshTokenAuth", "DoOnError", throwable1);
                                            application.logout();
                                        });
                            } else {
                                return Observable.just(1).doOnNext(o -> Log.i("RefreshTokenAuth", "Let's try another shot!"));
                            }
                        }
                    }
                    // No more retries. Pass the original Retrofit error through.
                    return Observable.error(throwable);
                }
            });
}

}

Answer 2

1） 使身份验证令牌的源缓存上一个成功结果提供使此缓存结果无效的方法：

class Auth {
    private Observable<AuthToken> validToken;

    synchronized void invalidateAuthToken() {
        validToken = null;
    }

    synchronized Observable<AuthToken> getAuthToken() {
        if (validToken == null) {
            validToken = repository
                .refreshToken(...) // start async request
                .doOnError(e -> invalidateAuthToken())
                .replay(1); // cache result
        }
        return validToken; // share among all subscribers
    }
}

2） 要访问web服务，请使用以下模式：

Observable<Data1> dataSource1 = 
    Observable.defer(auth.getAuthToken()) // always start from token
        .flatMap(token ->
            repository.fetchData1(token, ...)) // use token to call web service
        .doOnError(e -> auth.invalidateAuthToken())
        .retry(N); // retry N times