可以用OKHttp使用缓存中的数据时，离线改造可以用OKHttp使用缓存中的数据时，离线改造(Can

2019-05-09 04:16发布

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我试图用翻新与OKHttp缓存HTTP响应。 我跟着这个要点 ，并结束了这段代码： 

File httpCacheDirectory = new File(context.getCacheDir(), "responses");

HttpResponseCache httpResponseCache = null;
try {
     httpResponseCache = new HttpResponseCache(httpCacheDirectory, 10 * 1024 * 1024);
} catch (IOException e) {
     Log.e("Retrofit", "Could not create http cache", e);
}

OkHttpClient okHttpClient = new OkHttpClient();
okHttpClient.setResponseCache(httpResponseCache);

api = new RestAdapter.Builder()
          .setEndpoint(API_URL)
          .setLogLevel(RestAdapter.LogLevel.FULL)
          .setClient(new OkClient(okHttpClient))
          .build()
          .create(MyApi.class);

这是MyApi与缓存控制头

public interface MyApi {
   @Headers("Cache-Control: public, max-age=640000, s-maxage=640000 , max-stale=2419200")
   @GET("/api/v1/person/1/")
   void requestPerson(
           Callback<Person> callback
   );

首先，我在网上申请和查询缓存文件。 正确的JSON响应和头在那里。 但是，当我尝试请求下线，我总是得到RetrofitError UnknownHostException 。 还有什么我应该做的，使改造读取缓存的响应？

编辑：既然OKHttp 2.0.x的HttpResponseCache是Cache ， setResponseCache是setCache

Answer 1:

编辑改造2.X：

OkHttp拦截器是访问缓存离线时正确的方式：

1）的拦截器： 

private static final Interceptor REWRITE_CACHE_CONTROL_INTERCEPTOR = new Interceptor() {
    @Override public Response intercept(Chain chain) throws IOException {
        Response originalResponse = chain.proceed(chain.request());
        if (Utils.isNetworkAvailable(context)) {
            int maxAge = 60; // read from cache for 1 minute
            return originalResponse.newBuilder()
                    .header("Cache-Control", "public, max-age=" + maxAge)
                    .build();
        } else {
            int maxStale = 60 * 60 * 24 * 28; // tolerate 4-weeks stale
            return originalResponse.newBuilder()
                    .header("Cache-Control", "public, only-if-cached, max-stale=" + maxStale)
                    .build();
        }
    }

2）安装的客户端： 

OkHttpClient client = new OkHttpClient();
client.networkInterceptors().add(REWRITE_CACHE_CONTROL_INTERCEPTOR);

//setup cache
File httpCacheDirectory = new File(context.getCacheDir(), "responses");
int cacheSize = 10 * 1024 * 1024; // 10 MiB
Cache cache = new Cache(httpCacheDirectory, cacheSize);

//add cache to the client
client.setCache(cache);

3）添加客户端改造

Retrofit retrofit = new Retrofit.Builder()
        .baseUrl(BASE_URL)
        .client(client)
        .addConverterFactory(GsonConverterFactory.create())
        .build();

同时检查@kosiara -巴尔托什Kosarzycki的答案 。 您可能需要从响应删除一些头。

OKHttp 2.0.x的（检查原来的答案）：

由于OKHttp 2.0.x的HttpResponseCache是Cache ， setResponseCache是setCache 。 所以，你应该setCache这样的： 

        File httpCacheDirectory = new File(context.getCacheDir(), "responses");

        Cache cache = null;
        try {
            cache = new Cache(httpCacheDirectory, 10 * 1024 * 1024);
        } catch (IOException e) {
            Log.e("OKHttp", "Could not create http cache", e);
        }

        OkHttpClient okHttpClient = new OkHttpClient();
        if (cache != null) {
            okHttpClient.setCache(cache);
        }
        String hostURL = context.getString(R.string.host_url);

        api = new RestAdapter.Builder()
                .setEndpoint(hostURL)
                .setClient(new OkClient(okHttpClient))
                .setRequestInterceptor(/*rest of the answer here */)
                .build()
                .create(MyApi.class);

原来的答案：

事实证明，服务器的响应必须具有Cache-Control: public作出OkClient从缓存中读取。

此外，如果你想从网络请求的时候用，你应该添加Cache-Control: max-age=0请求头。 这样的回答显示了如何做参数。 这是我如何使用它： 

RestAdapter.Builder builder= new RestAdapter.Builder()
   .setRequestInterceptor(new RequestInterceptor() {
        @Override
        public void intercept(RequestFacade request) {
            request.addHeader("Accept", "application/json;versions=1");
            if (MyApplicationUtils.isNetworkAvailable(context)) {
                int maxAge = 60; // read from cache for 1 minute
                request.addHeader("Cache-Control", "public, max-age=" + maxAge);
            } else {
                int maxStale = 60 * 60 * 24 * 28; // tolerate 4-weeks stale
                request.addHeader("Cache-Control", 
                    "public, only-if-cached, max-stale=" + maxStale);
            }
        }
});


Answer 2:

所有anwsers的上面并没有为我工作。 我试图实施改造2.0.0-β2脱机缓存。 我添加使用拦截器okHttpClient.networkInterceptors()方法，但收到java.net.UnknownHostException当我试图缓存脱机使用。 原来，我不得不添加okHttpClient.interceptors()为好。

但问题是，高速缓存未写入闪存，因为服务器返回Pragma:no-cache防止OkHttp从存储的响应。 离线缓存甚至修改请求标头值后没有工作。 经过一些试验和错误，我得到了缓存，而不由效应初探，而不是要求删除编译修改后端侧的工作- response.newBuilder().removeHeader("Pragma");

改造：2.0.0-β2; OkHttp：2.5.0 

OkHttpClient okHttpClient = createCachedClient(context);
Retrofit retrofit = new Retrofit.Builder()
        .client(okHttpClient)
        .baseUrl(API_URL)
        .addConverterFactory(GsonConverterFactory.create())
        .build();
service = retrofit.create(RestDataResource.class);

... 

private OkHttpClient createCachedClient(final Context context) {
    File httpCacheDirectory = new File(context.getCacheDir(), "cache_file");

    Cache cache = new Cache(httpCacheDirectory, 20 * 1024 * 1024);
    OkHttpClient okHttpClient = new OkHttpClient();
    okHttpClient.setCache(cache);
    okHttpClient.interceptors().add(
            new Interceptor() {
                @Override
                public Response intercept(Chain chain) throws IOException {
                    Request originalRequest = chain.request();
                    String cacheHeaderValue = isOnline(context) 
                        ? "public, max-age=2419200" 
                        : "public, only-if-cached, max-stale=2419200" ;
                    Request request = originalRequest.newBuilder().build();
                    Response response = chain.proceed(request);
                    return response.newBuilder()
                        .removeHeader("Pragma")
                        .removeHeader("Cache-Control")
                        .header("Cache-Control", cacheHeaderValue)
                        .build();
                }
            }
    );
    okHttpClient.networkInterceptors().add(
            new Interceptor() {
                @Override
                public Response intercept(Chain chain) throws IOException {
                    Request originalRequest = chain.request();
                    String cacheHeaderValue = isOnline(context) 
                        ? "public, max-age=2419200" 
                        : "public, only-if-cached, max-stale=2419200" ;
                    Request request = originalRequest.newBuilder().build();
                    Response response = chain.proceed(request);
                    return response.newBuilder()
                        .removeHeader("Pragma")
                        .removeHeader("Cache-Control")
                        .header("Cache-Control", cacheHeaderValue)
                        .build();
                }
            }
    );
    return okHttpClient;
}

... 

public interface RestDataResource {

    @GET("rest-data") 
    Call<List<RestItem>> getRestData();

}


Answer 3:

我的解决方案： 

private BackendService() {

    httpCacheDirectory = new File(context.getCacheDir(),  "responses");
    int cacheSize = 10 * 1024 * 1024; // 10 MiB
    Cache cache = new Cache(httpCacheDirectory, cacheSize);

    httpClient = new OkHttpClient.Builder()
            .addNetworkInterceptor(REWRITE_RESPONSE_INTERCEPTOR)
            .addInterceptor(OFFLINE_INTERCEPTOR)
            .cache(cache)
            .build();

    Retrofit retrofit = new Retrofit.Builder()
            .baseUrl("https://api.backend.com")
            .client(httpClient)
            .addConverterFactory(GsonConverterFactory.create())
            .build();

    backendApi = retrofit.create(BackendApi.class);
}

private static final Interceptor REWRITE_RESPONSE_INTERCEPTOR = chain -> {
    Response originalResponse = chain.proceed(chain.request());
    String cacheControl = originalResponse.header("Cache-Control");

    if (cacheControl == null || cacheControl.contains("no-store") || cacheControl.contains("no-cache") ||
            cacheControl.contains("must-revalidate") || cacheControl.contains("max-age=0")) {
        return originalResponse.newBuilder()
                .header("Cache-Control", "public, max-age=" + 10)
                .build();
    } else {
        return originalResponse;
    }
};

private static final Interceptor OFFLINE_INTERCEPTOR = chain -> {
    Request request = chain.request();

    if (!isOnline()) {
        Log.d(TAG, "rewriting request");

        int maxStale = 60 * 60 * 24 * 28; // tolerate 4-weeks stale
        request = request.newBuilder()
                .header("Cache-Control", "public, only-if-cached, max-stale=" + maxStale)
                .build();
    }

    return chain.proceed(request);
};

public static boolean isOnline() {
    ConnectivityManager cm = (ConnectivityManager) MyApplication.getApplication().getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo netInfo = cm.getActiveNetworkInfo();
    return netInfo != null && netInfo.isConnectedOrConnecting();
}


Answer 4:

答案是肯定的，基于上述的答案，我开始写单元测试，以验证所有可能的使用情况：

  • 离线时使用高速缓存
  • 首先使用缓存的响应，直至过期，则网络
  • 使用网络第一，然后缓存某些请求
  • 不要在高速缓存中存储了一些回应

我建立了一个小帮手LIB轻松配置OKHttp缓存，可以看到相关的单元测试这里Github上： https://github.com/ncornette/OkCacheControl/blob/master/okcache-control/src/test/java/com/ ncornette /缓存/ OkCacheControlTest.java

单元测试，演示如何使用缓存时离线： 

@Test
public void test_USE_CACHE_WHEN_OFFLINE() throws Exception {
    //given
    givenResponseInCache("Expired Response in cache", -5, MINUTES);
    given(networkMonitor.isOnline()).willReturn(false);

    //when
    //This response is only used to not block when test fails
    mockWebServer.enqueue(new MockResponse().setResponseCode(404));
    Response response = getResponse();

    //then
    then(response.body().string()).isEqualTo("Expired Response in cache");
    then(cache.hitCount()).isEqualTo(1);
}

正如你所看到的，高速缓存可以使用，即使它已过期。 希望这将有助于。



Answer 5:

在@ kosiara-巴尔托什-kasarzycki的建筑答案 ，我用改装，okhttp，rxjava和番石榴创建正确地从内存- >基于磁盘加载一个样本项目>网络。 https://github.com/digitalbuddha/StoreDemo



Answer 6:

缓存与Retrofit2和OkHTTP3： 

OkHttpClient client = new OkHttpClient
  .Builder()
  .cache(new Cache(App.sApp.getCacheDir(), 10 * 1024 * 1024)) // 10 MB
  .addInterceptor(new Interceptor() {
    @Override public Response intercept(Chain chain) throws IOException {
      Request request = chain.request();
      if (NetworkUtils.isNetworkAvailable()) {
        request = request.newBuilder().header("Cache-Control", "public, max-age=" + 60).build();
      } else {
        request = request.newBuilder().header("Cache-Control", "public, only-if-cached, max-stale=" + 60 * 60 * 24 * 7).build();
      }
      return chain.proceed(request);
    }
  })
  .build();

NetworkUtils.isNetworkAvailable（）静态方法： 

public static boolean isNetworkAvailable(Context context) {
        ConnectivityManager cm =
                (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
        return activeNetwork != null &&
                activeNetwork.isConnectedOrConnecting();
    }

然后，只需添加客户端改造建设者： 

Retrofit retrofit = new Retrofit.Builder()
                    .baseUrl(BASE_URL)
                    .client(client)
                    .addConverterFactory(GsonConverterFactory.create())
                    .build();

原始来源： https://newfivefour.com/android-retrofit2-okhttp3-cache-network-request-offline.html



文章来源: Can Retrofit with OKHttp use cache data when offline
标签： caching retrofit okhttp offline-caching retrofit2
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