我在下面有这个简单的代码，模拟我正在尝试完成的场景
mApiService.api().postSomethingWithAccessToken(request, "some_invalid_access_token")
.subscribeOn(Schedulers.io())
.retryWhen(new Function<Observable<Throwable>, ObservableSource<AccessToken>>() {
@Override
public ObservableSource<AccessToken> apply(Observable<Throwable> throwableObservable) throws Exception {
return mApiService.api().getAccessToken();
}
})
.subscribeOn(Schedulers.io())
.subscribe(new Observer<Void>() {
@Override
public void onSubscribe(Disposable d) {
}
@Override
public void onNext(Void value) {
}
@Override
public void onError(Throwable e) {
e.printStackTrace();
onError(e);
}
@Override
public void onComplete() {
}
});
我只是列举它以明确我的目标：
基于上面的代码以及我目前对 .retryWhen（）的理解，如果原始可观察上发生错误，它将会执行（。 postSomethingWithAccessToken（）），并在必要时重试（根据你在重试中的条件），这里发生的是 .retryWhen（）首先在外部Observable之前执行，导致不需要的重复请求， 根据我目前的理解（代码），我怎样才能实现上面提到的那些东西？任何帮助将不胜感激。 ：（
编辑：当前解决方法：
mApiService.api().postSomethingWithAccessToken(request, preferences.getString("access_token", ""))
.subscribeOn(Schedulers.io())
.retryWhen(new Function<Observable<Throwable>, ObservableSource<?>>() {
@Override
public ObservableSource<?> apply(final Observable<Throwable> throwableObservable) throws Exception {
return throwableObservable.flatMap(new Function<Throwable, ObservableSource<?>>() {
@Override
public ObservableSource<?> apply(Throwable throwable) throws Exception {
if (throwable instanceof HttpException) {
HttpException httpException = (HttpException) throwable;
if (httpException.code() == 401) {
return mApiService.api().getAccessToken()
.doOnNext(new Consumer<Authentication>() {
@Override
public void accept(Authentication authentication) throws Exception {
update(authentication);
}
});
}
}
return Observable.error(throwable);
}
});
}
})
.subscribe(new Observer<Void>() {
@Override
public void onSubscribe(Disposable d) {
Log.e("subscribe", "TOKEN : " + preferences.getString("access_token", ""));
}
@Override
public void onNext(Void value) {
Log.e("onNext", "TOKEN : " + preferences.getString("access_token", ""));
}
@Override
public void onError(Throwable e) {
e.printStackTrace();
}
@Override
public void onComplete() {
Log.e("Complete", "____ COMPLETE");
}
});
通过共享偏好更新令牌的方法
public void update(Authentication authentication) {
preferences.edit().putString("access_token", authentication.getAccessToken()).commit();
}
我注意到（我把一个Log）外部observable的订阅和retryWhen在主线程上执行，但是重试/重新订阅的流正跳过不同的Scheduler的线程，看起来像竞争条件：（
onSubscrbie_outer_observable: Thread[main,5,main]
RetryWhen: Thread[main,5,main]
Throwable_FlatMap: Thread[RxCachedThreadScheduler-1,5,main]
doOnNext(Token_Refresh): Thread[RxCachedThreadScheduler-1,5,main]
Throwable_FlatMap: Thread[RxCachedThreadScheduler-2,5,main]
doOnNext(Token_Refresh): Thread[RxCachedThreadScheduler-2,5,main]
Throwable_FlatMap: Thread[RxCachedThreadScheduler-1,5,main]
doOnNext(Token_Refresh): Thread[RxCachedThreadScheduler-1,5,main]
// and so on...
答案 0 :(得分：3)
这里几乎没有问题：
postSomethingWithAccessToken方法，否则您只需使用相同的旧无效访问令牌重试。Observable并将你的重试逻辑放在那里。正如您所说的那样，首先执行此方法，而不是在发生错误时，throwableObservable是对错误的响应，它会将错误视为排放（onNext()），您可以flatMap()每个错误并且响应错误（用于向源流传递错误）完成，或者使用onNext()并使用某个对象发出信号进行重试。所以你需要：
1）将访问令牌存储在可以使用访问令牌刷新进行更改的地方
2）在逻辑正确响应错误时修复重试
以下是建议代码：
postSomethingWithAccessToken(request, accessToken)
.subscribeOn(Schedulers.io())
.retryWhen(new Function<Observable<Throwable>, ObservableSource<?>>() {
@Override
public ObservableSource<?> apply(
@NonNull Observable<Throwable> throwableObservable) throws Exception {
return throwableObservable.flatMap(
new Function<Throwable, ObservableSource<? extends R>>() {
@Override
public ObservableSource<? extends R> apply(
@NonNull Throwable throwable) throws Exception {
if (throwable.code == 401) { //or 404/403, just a pseudo-code, put your real error comparing logic here
return getAccessToken()
.doOnNext(refreshedToken -> accessToken.updateToken(refreshedToken));
//or keep accessToken on some field, the point to have mutable
//var that you can change and postSomethingWithAccessToken can see
}
return Observable.error(throwable);
}
});
}
}
)
.subscribeOn(Schedulers.io())
.subscribe(new Consumer<Result>() {
@Override
public void accept(@NonNull Result result) throws Exception {
//handle result
}
}
);
答案 1 :(得分：1)
非常感谢yosriz指出我正确的方向来解决我的磨牙问题，我必须使用defer。所以我最终在GitHub中遇到了这个问题，Why resubscribe the source observable emit same output when I use retryWhen operator?
这与我现在遇到的问题完全相同，因为在这里遇到同样问题的任何人都是我的解决方案。
Observable
.defer(new Callable<ObservableSource<?>>() {
@Override
public ObservableSource<?> call() throws Exception {
// return an observable source here, the observable that will be the source of the entire stream;
}
})
.subscribeOn( /*target thread to run*/ )
.retryWhen( {
// return a throwable observable here that will perform the logic when an error occurred
})
.subscribe( /*subscription here*/ )
或者这是我的解决方案的完整非lambda
Observable
.defer(new Callable<ObservableSource<?>>() {
@Override
public ObservableSource<?> call() throws Exception {
return mApiService.api().postSomethingWithAccessToken(
request, preferences.getString("access_token", ""));
}
})
.subscribeOn(Schedulers.io())
.retryWhen(new Function<Observable<Throwable>, ObservableSource<?>>() {
@Override
public ObservableSource<?> apply(final Observable<Throwable> throwableObservable) throws Exception {
return throwableObservable.flatMap(new Function<Throwable, ObservableSource<?>>() {
@Override
public ObservableSource<?> apply(Throwable throwable) throws Exception {
if (throwable instanceof HttpException) {
HttpException httpException = (HttpException) throwable;
if (httpException.code() == 401) {
return mApiService.api().getAccessToken().doOnNext(new Consumer<Authentication>() {
@Override
public void accept(Authentication authentication) throws Exception {
update(authentication);
}
});
}
}
return Observable.error(throwable);
}
});
}
})
.subscribe(new Observer<Void>() {
@Override
public void onSubscribe(Disposable d) {
Log.e("subscribe", "TOKEN : " + preferences.getString("access_token", ""));
}
@Override
public void onNext(Void value) {
Log.e("onNext", "TOKEN : " + preferences.getString("access_token", ""));
}
@Override
public void onError(Throwable e) {
e.printStackTrace();
}
@Override
public void onComplete() {
Log.e("Complete", "____ COMPLETE");
}
});
这里的关键点是“当.retryWhen()运算符重新订阅源可观察时，如何修改/更新现有的源可观察源”
答案 2 :(得分：0)
我试图在这里解决同样的问题，我试图复制上面的解决方案，它确实刷新了令牌，但是当我的令牌更新时没有尝试重试请求。
这是我没有lambda的代码：
public Observable<Estabelecimento> listarEstabelecimentos() {
return Observable.defer(new Callable<ObservableSource<? extends Estabelecimento>>() {
@Override
public ObservableSource<? extends Estabelecimento> call() throws Exception {
return mGetNetAPI.listarEstabelecimento()
.map(mNetworkErrorHandler::processError);
}
}).retryWhen(throwableObservable -> throwableObservable.flatMap(new Function<Throwable, ObservableSource<?>>() {
@Override
public ObservableSource<?> apply(@NonNull Throwable throwable) throws Exception {
if (throwable instanceof UnauthorizedException) {
return mRequestManager.getTokenObservable(AutoAtendimentoApplication.getContext())
.doOnNext(new Consumer<AuthResponse>() {
@Override
public void accept(@NonNull AuthResponse response) throws Exception {
Log.i("NEXT", "OK");
}
}).doOnError(new Consumer<Throwable>() {
@Override
public void accept(@NonNull Throwable throwable) throws Exception {
Log.i("ONERROR", "NOT OK");
}
});
}
return Observable.error(throwable);
}
}
));
}
任何想法我可能做错了吗？