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RxJava retryWhen操作符實現錯誤重試機制

來源：程序員人生發布時間：2016-06-23 08:08:56 閱讀次數：3912次

業務需求

當我們在app里發起網絡要求時，可能會由于各種問題致使失敗。如何利用RxJava來實現出現毛病后重試若干次，并且可以設定重試的時間間隔。

具體實現

網絡要求使用Retrofit來做，還是使用上篇博客中的要求用戶信息接口

    @GET("/userinfo?noToken=1")
    Observable<Response> getUserInfoNoToken();

下面是要求用戶信息接口的邏輯代碼

userApi.getUserInfoNoToken()
                        //總共重試3次，重試間隔3000毫秒
                        .retryWhen(new RetryWithDelay(3, 3000))
                        .observeOn(AndroidSchedulers.mainThread())
                        .subscribeOn(Schedulers.io())
                        .subscribe(new Action1<Response>() {
                            @Override
                            public void call(Response response) {
                                String content = new String(((TypedByteArray) response.getBody()).getBytes());
                                printLog(tvLogs, "", content);
                            }
                        }, new Action1<Throwable>() {
                            @Override
                            public void call(Throwable throwable) {
                                throwable.printStackTrace();
                            }
                        });

RetryWithDelay

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

        private final int maxRetries;
        private final int retryDelayMillis;
        private int retryCount;

        public RetryWithDelay(int maxRetries, int retryDelayMillis) {
            this.maxRetries = maxRetries;
            this.retryDelayMillis = retryDelayMillis;
        }

        @Override
        public Observable<?> call(Observable<? extends Throwable> attempts) {
            return attempts
                    .flatMap(new Func1<Throwable, Observable<?>>() {
                        @Override
                        public Observable<?> call(Throwable throwable) {
                            if (++retryCount <= maxRetries) {
                                // When this Observable calls onNext, the original Observable will be retried (i.e. re-subscribed).
                                printLog(tvLogs, "", "get error, it will try after " + retryDelayMillis
                                        + " millisecond, retry count " + retryCount);
                                return Observable.timer(retryDelayMillis,
                                        TimeUnit.MILLISECONDS);
                            }
                            // Max retries hit. Just pass the error along.
                            return Observable.error(throwable);
                        }
                    });
        }
    }

如何摹擬重試呢？

方法1：把服務器關閉，關閉服務器后，客戶端要求接口的必定會報錯，看看是否是重試3次。

運行輸出：

'get error, it will try after 3000 millisecond, retry count 1'
Main Thread:false, Thread Name:Retrofit-Idle

'get error, it will try after 3000 millisecond, retry count 2'
Main Thread:false, Thread Name:Retrofit-Idle

'get error, it will try after 3000 millisecond, retry count 3'
Main Thread:false, Thread Name:Retrofit-Idle

上面是重試3次了，但是我們怎樣知道，如果在服務器啟動后，在接下的重試中要求成功呢？接下來試試方法2。

方法2：先把服務器關閉，當點擊按鈕要求的同時，啟動Tomcat服務器。

運行輸出：

'get error, it will try after 3000 millisecond, retry count 1'
Main Thread:false, Thread Name:Retrofit-Idle

'get error, it will try after 3000 millisecond, retry count 2'
Main Thread:false, Thread Name:Retrofit-Idle

'username:chiclaim,age:007'
Main Thread:true, Thread Name:main