1

我正在尝试使用 Retrofit 和 OkHttp 来实现缓存。这是我已经完成的：

private static final Interceptor REWRITE_CACHE_CONTROL_INTERCEPTOR = new Interceptor() {

        @Override public Response intercept(Interceptor.Chain chain) throws IOException {
            Request originalRequest = chain.request();
            Request.Builder request = originalRequest.newBuilder();
            Response response = chain.proceed(request.build());
            return response.newBuilder()
                    .removeHeader("Pragma")
                    .removeHeader("Cache-Control")
                    .header("Cache-Control", "max-age=2419200")
                    .build();
        }
    };

    @Provides
    @Singleton
    OkHttpClient provideHttpClient(Context context) {


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


        HttpLoggingInterceptor oggingInterceptor = new HttpLoggingInterceptor();
        oggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
        return new OkHttpClient.Builder()
                .cache(cache)
                .connectTimeout(3, TimeUnit.SECONDS)
                .writeTimeout(3, TimeUnit.SECONDS)
                .readTimeout(3, TimeUnit.SECONDS)
                .addInterceptor(REWRITE_CACHE_CONTROL_INTERCEPTOR)
                .addInterceptor(oggingInterceptor).build();
    }

然后我将此拦截器添加到 HTTP 客户端：

.addInterceptor(REWRITE_CACHE_CONTROL_INTERCEPTOR)

我的响应目录中有文件，但是当我尝试在没有互联网连接的情况下加载内容时，它给了我以下错误：

无法解析主机“example.com”：没有与主机名关联的地址

我只想将我的 http 响应存储在某处并在没有互联网连接的情况下加载它。

如果有互联网连接，我想重写缓存。

4

2 回答 2

4

我和你遇到了同样的问题，现在我找到了一篇文章并解决了我的问题，我认为它可以帮助你。

因为在获取缓存的时间之外，okhttp会清空缓存并再次请求服务器，现在缓存是空的，所以它会发送错误异常。

我们可以使用您的拦截器设置一些请求设置。

CacheControl.Builder cacheBuilder = new CacheControl.Builder();
            cacheBuilder.maxAge(0, TimeUnit.SECONDS);
            cacheBuilder.maxStale(365,TimeUnit.DAYS);
            CacheControl cacheControl = cacheBuilder.build();

            Request request = chain.request();
            if(!StateUtils.isNetworkAvailable(MyApp.mContext)){
                request = request.newBuilder()
                        .cacheControl(cacheControl)
                        .build();
            }

maxAge ：控制缓存寿命最大值

maxStale : 控制缓存过期时间

完整代码：

weiBoApiRetrofit() {

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

        OkHttpClient client = new OkHttpClient.Builder()
                .addNetworkInterceptor(REWRITE_CACHE_CONTROL_INTERCEPTOR)
                .cache(cache).build();

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

        WeiBoApiService = retrofit.create(WeiBoApi.class);
    }

    //cache
    Interceptor REWRITE_CACHE_CONTROL_INTERCEPTOR = new Interceptor() {
        @Override
        public Response intercept(Chain chain) throws IOException {

            CacheControl.Builder cacheBuilder = new CacheControl.Builder();
            cacheBuilder.maxAge(0, TimeUnit.SECONDS);
            cacheBuilder.maxStale(365,TimeUnit.DAYS);
            CacheControl cacheControl = cacheBuilder.build();

            Request request = chain.request();
            if(StateUtils.isNetworkAvailable(MyApp.mContext)){
                request = request.newBuilder()
                        .cacheControl(cacheControl)
                        .build();
            }
            Response originalResponse = chain.proceed(request);
            if (StateUtils.isNetworkAvailable(MyApp.mContext)) {
                int maxAge = 60  * 60; // read from cache
                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();
            }
        }
    };
}

我可以解决我的问题。

但我不知道为什么在 Interceptor Useless 的响应中设置标头，有人说“拦截器必须设置这两个请求和响应”

我希望我能帮助你。

于 2016-07-28T06:29:56.840 回答
3

以这种方式设置标题（正好是 50000）解决了这个问题。 

.header("Cache-Control", String.format("max-age=%d", 50000))
于 2016-04-20T08:50:54.330 回答