RxJava中发生错误后如何更改重试请求中的参数

Question

我向具有改造2.0的服务器发送登录请求，并且服务器返回到客户端会话令牌，但我必须在其他请求中使用该令牌，但是此令牌的生存期有限，并且当它到期时，服务器将返回HTTP错误401。

遇到此错误后，我尝试通过以下代码进行重新登录：

    holder.getApi(GuideProfileApi.class)
      .getProfile(String.valueOf(holder.getServerId()), holder.getServerToken())
      .subscribeOn(Schedulers.io())
      .retryWhen(new Function<Observable<Throwable>, ObservableSource<?>>() {
         @Override
         public ObservableSource<?> apply(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)throwable).code() == 401) {
                 RegistryLoginResult loginResult = holder.login().blockingSingle();
                 return holder.getApi(GuideProfileApi.class)
                    .getProfile(String.valueOf(loginResult.getUserId()), loginResult.getSessionToken());
               }
               return Observable.error(throwable);
            }
        });
     }
  })
  .observeOn(AndroidSchedulers.mainThread())
  .subscribe(new Consumer<ProfileResult>() {
    @Override
    public void accept(ProfileResult profileResult) throws Exception {
      Log.d("Result", profileResult.toString());
    }
  }, new Consumer<Throwable>() {
      @Override
      public void accept(Throwable throwable) throws Exception {
        Log.e("Result", throwable.getLocalizedMessage());
      }
});

并且发送了重试请求，但是请求的参数与不正确的请求中的参数相同（重新登录之前）。如何在再次发送请求之前更改请求的参数？

Answer 1

您可以使用retryWhen，但是问题是您的retryWhen重试了您在惰性时间内创建的同一可观察对象。您的解决方案是使用运算符defer获取host（），因为延迟它不是在您定义可观察对象时创建可观察对象，而是在被订阅者使用时创建它。

Observable.defer(()-> holder.getApi(GuideProfileApi.class)
          .getProfile(String.valueOf(holder.getServerId()),holder.getServerToken()))
  .subscribeOn(Schedulers.io())
  .retryWhen(new Function<Observable<Throwable>, ObservableSource<?>>() {
     @Override
     public ObservableSource<?> apply(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)throwable).code() == 401) {
             RegistryLoginResult loginResult = holder.login().blockingSingle();
             return holder.getApi(GuideProfileApi.class)
                .getProfile(String.valueOf(loginResult.getUserId()), loginResult.getSessionToken());
           }
           return Observable.error(throwable);
        }
    });
 }
  })
  .observeOn(AndroidSchedulers.mainThread())
  .subscribe(new Consumer<ProfileResult>() {
    @Override
    public void accept(ProfileResult profileResult) throws Exception {
      Log.d("Result", profileResult.toString());
    }
      }, new Consumer<Throwable>() {
          @Override
          public void accept(Throwable throwable) throws Exception {
            Log.e("Result", throwable.getLocalizedMessage());
          }
    });

您可以在此处查看重试的一些示例https://github.com/politrons/reactive/blob/master/src/test/java/rx/observables/errors/ObservableExceptions.java

Answer 2

您使用了错误的运营商。如果遇到错误，retryWhen将重试您的原始可观察值。你需要的是onErrorResumeNext. 就像是

 holder.getApi(GuideProfileApi.class)
      .getProfile(String.valueOf(holder.getServerId()), holder.getServerToken())
      .subscribeOn(Schedulers.io())
      .onErrorResumeNext(new Function<Throwable, ObservableSource<?>>() {
        @Override
         public ObservableSource<?> apply(Throwable throwable) {
               if (throwable instanceof HttpException &&  ((HttpException)throwable).code() == 401) {
                 RegistryLoginResult loginResult = holder.login().blockingSingle();
                 return holder.getApi(GuideProfileApi.class)
                    .getProfile(String.valueOf(loginResult.getUserId()), loginResult.getSessionToken());
               }
               return Observable.error(throwable);
        }
    }) 
  .observeOn(AndroidSchedulers.mainThread())
  .subscribe(new Consumer<ProfileResult>() {
    @Override
    public void accept(ProfileResult profileResult) throws Exception {
      Log.d("Result", profileResult.toString());
    }
  }, new Consumer<Throwable>() {
      @Override
      public void accept(Throwable throwable) throws Exception {
        Log.e("Result", throwable.getLocalizedMessage());
      }
});