RxJava - 等到 retryWhen 完成其他活动/片段中的其他可观察对象

Question

用例：我正在开发一个 Android 应用程序，它有一个带有 4 个标签的 viewpager，它们都是 Fragments。对于每个选项卡/片段，我必须每 5 分钟使用 Oauth 和令牌过期连接到 REST Api。

当前解决方案： 使用 RxJava 和 retryWhen 运算符我可以在收到 401 HTTP 错误时重新进行身份验证。对于每个订阅和消费的 Observable 流并使用：

retryWhen(refreshTokenAuthenticator)

因此，当令牌过期时，流会使用它，然后执行真正的 api 调用。

问题：这仅适用于一个订阅中消耗的一个 observable，但考虑到 401 错误可能随时出现，我需要允许用户在标签之间切换而不阻止他/她在任何 Api 调用的任何片段中。

问题：有没有办法让 observables 等待其他 observables 用 onNext() 结束，它们不在同一个流/订阅者中？实际上在不同的片段中？所以api调用场景会是这样的：

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)

几乎同时...

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 调用看起来都差不多：

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);

}

还有我的 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

1) 使身份验证令牌的源缓存上一个成功的结果 + 提供方法使这个缓存的结果无效：

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

Answer 2

如果应用当前是否正在重新进行身份验证，最后只需添加一个全局（在我的 Application 类中）布尔值即可。它实际上允许两个 401 HTTP 错误，但第二个在 onNext() 中继续并重新执行初始 observable。我想做一些更具反应性的事情，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);
                }
            });
}

}