Retrofit2 - 如何仅缓存某些 API 调用

Question

我只想缓存某些调用，而不是全部。这是我现在拥有的代码，但它会影响所有改造调用：

int cacheSize = 10 * 1024 * 1024; // 10 MB  
Cache cache = new Cache(getCacheDir(), cacheSize);

OkHttpClient okHttpClient = new OkHttpClient.Builder()
    .cache(cache)
    .build();

Retrofit.Builder builder = new Retrofit.Builder()  
    .baseUrl("http://10.0.2.2:3000/")
    .client(okHttpClient)
    .addConverterFactory(GsonConverterFactory.create());

Retrofit retrofit = builder.build(); 

当我只想为那个调用做缓存时，我可以在标题中放入一些东西吗？

例如：

// 我在想我可以在标题中放一些东西。我只想缓存客户端（android）端的调用。所以我在想改造可以记住响应并将其缓存以供下一次调用，但我不希望它用于我所有的调用，只是我想要的那些，可能是 1 或 2。其余的可以一直连接到服务器。这是如何实现的？

@Headers("Cache-Control:????XXXXX) //is it possible this way ?, how ?
@GET("getBusiness.action")// Store information 
Call<RestaurantInfoModel> getRestaurantInfo(@Query("userId") String userId,@Query("businessId") String businessId);

更新：

这是我现在尝试过的：

这是我构建 okhttpclient 的方法：

final OkHttpClient.Builder builder = new OkHttpClient.Builder();
int cacheSize = 10 * 1024 * 1024; // 10 MB
Cache cache = new Cache(getCacheDir(), cacheSize);
if (BuildConfig.RETROFIT_LOG_ALL) {
    HttpLoggingInterceptor logging = new HttpLoggingInterceptor();
    logging.setLevel(HttpLoggingInterceptor.Level.BODY);
    builder.addInterceptor(logging);
}
builder.cache(cache);
return builder.build();

稍后我将它添加到改造中，它可以工作，但似乎没有缓存。让我们在不向 okhttp 添加缓存的情况下查看标头响应：

Content-Type: application/json; charset=utf-8
06-18 17:54:58.044 11233-11735/com.mobile.myapp.staging D/OkHttp: Connection: close
06-18 17:54:58.044 11233-11735/com.mobile.myapp.staging D/OkHttp: Transfer-Encoding: chunked
06-18 17:54:58.044 11233-11735/com.mobile.myapp.staging D/OkHttp: X-Powered-By: Express
06-18 17:54:58.044 11233-11735/com.mobile.myapp.staging D/OkHttp: Vary: Origin
06-18 17:54:58.044 11233-11735/com.mobile.myapp.staging D/OkHttp: Access-Control-Allow-Credentials: true
06-18 17:54:58.044 11233-11735/com.mobile.myapp.staging D/OkHttp: Cache-Control: public, max-age=0
06-18 17:54:58.044 11233-11735/com.mobile.myapp.staging D/OkHttp: ETag: W/"39ba-G9evSsiVDp9GAVGu1Mk4ag"
06-18 17:54:58.044 11233-11735/com.mobile.myapp.staging D/OkHttp: Date: Sun, 18 Jun 2017 10:54:58 GMT

所以这是我为查看缓存是否正常工作所做的测试。我使用这个向 api 发出请求：

public interface CountriesApi {
    @GET("countries")
    @Headers({"Content-Type:application/json"})
    Observable<List<CountryModel>> getCountries();
}

然后我在 android 设备上关闭互联网并尝试在应用程序中再次拨打相同的电话。但相反，我得到了改造，抱怨没有网络连接。相反，它应该刚刚从缓存中获取。知道有什么问题吗？

java.net.SocketException: Network is unreachable at
java.net.PlainSocketImpl.socketConnect(Native Method) at
java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:334) at
java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:196)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:178) at
java.net.SocksSocketImpl.connect(SocksSocketImpl.java:356) at
java.net.Socket.connect(Socket.java:586) at
okhttp3.internal.platform.AndroidPlatform.connectSocket(AndroidPlatform.java:63)
at
okhttp3.internal.connection.RealConnection.connectSocket(RealConnection.java:223)
at okhttp3.internal.connection.RealConnection.connect(RealConnection.java:149)
at
okhttp3.internal.connection.StreamAllocation.findConnection(StreamAllocation.java:192)
at
okhttp3.internal.connection.StreamAllocation.findHealthyConnection(StreamAllocation.java:121)
at
okhttp3.internal.connection.StreamAllocation.newStream(StreamAllocation.java:100)
at
okhttp3.internal.connection.ConnectInterceptor.intercept(ConnectInterceptor.java:42)
at
okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:92)
at
okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:67)
at okhttp3.internal.cache.CacheInterceptor.intercept(CacheInterceptor.java:93)
at
okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:92)
at
okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:67)
at okhttp3.internal.http.BridgeInterceptor.intercept(BridgeInterceptor.java:93)
at
okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:92)
at
okhttp3.internal.http.RetryAndFollowUpInterceptor.intercept(RetryAndFollowUpInterceptor.java:120)
at
okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:92)
at
okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:67)
at
okhttp3.logging.HttpLoggingInterceptor.intercept(HttpLoggingInterceptor.java:211)
at
okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:92)
at
okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:67)
at
com.mobile.retrofit.NetworkSessionManager.intercept(NetworkSessionManager.java:38)
at
okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:92)
at
okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:67)
at okhttp3.RealCall.getResponseWithInterceptorChain(RealCall.java:185) at
okhttp3.RealCall.execute(RealCall.java:69) at
retrofit2.OkHttpCall.execute(OkHttpCall.java:180) at
retrofit2.adapter.rxjava2.CallExecuteObservable.subscribeActual(CallExecuteObservable.java:41)
at io.reactivex.Observable.subscribe(Observable.java:10842) at
retrofit2.adapter.rxjava2.BodyObservable.subscribeActual(BodyObservable.java:34)
at io.reactivex.Observable.subscribe(Observable.java:10842) at
io.reactivex.internal.operators.observable.ObservableFlatMap.subscribeActual(ObservableFlatMap.java:55)
at io.reactivex.Observable.subscribe(Observable.java:10842) at
io.reactivex.internal.operators.observable.ObservableSubscribeOn$SubscribeTask.run(ObservableSubscribeOn.java:96)
at io.reactivex.Scheduler$DisposeTask.run(Scheduler.java:452) at
io.reactivex.internal.schedulers.ScheduledRunnable.run(ScheduledRunnable.java:61)
at
io.reactivex.internal.schedulers.ScheduledRunnable.call(ScheduledRunnable.java:52)
at java.util.concurrent.FutureTask.run(FutureTask.java:237) at
java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:272)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607)
at java.lang.Thread.run(Thread.java:761) 

Answer 1

我也在寻找相同的解决方案，他们想出了这个解决方案：

首先创建一个单例改造类：

public class RetrofitClient {

private static final String BASE_URL = "BASE URL HERE...";

private static RetrofitClient mInstance;

private final Retrofit retrofit;
private final Retrofit retrofitCache;

private static final String HEADER_CACHE_CONTROL = "Cache-Control";
private static final String HEADER_PRAGMA = "Pragma";
int cacheSize = 10 * 1024 * 1024; // 10 MB

public static synchronized RetrofitClient getInstance(Context context) {
    if (mInstance == null) {
        mInstance = new RetrofitClient(context);
    }
    return mInstance;
}

private RetrofitClient(Context context) {
    retrofit = new Retrofit.Builder()
            .baseUrl(BASE_URL)
            .addConverterFactory(GsonConverterFactory.create())
            .build();

    retrofitCache = new Retrofit.Builder()
            .baseUrl(BASE_URL)
            .client(okHttpClient(context))
            .addConverterFactory(GsonConverterFactory.create())
            .build();

}

public ApiInterface getApi() {
    return retrofit.create(ApiInterface.class);
}

public ApiInterface getCachedApi() {
    return retrofitCache.create(ApiInterface.class);
}

Interceptor networkInterceptor() {
    return chain -> {
        CacheControl cacheControl = new CacheControl.Builder()
                .maxAge(5, TimeUnit.MINUTES) //cache validity time
                .build();

        Response response = chain.proceed(chain.request());

        return response.newBuilder()
                .removeHeader(HEADER_PRAGMA)
                .removeHeader(HEADER_CACHE_CONTROL)
                .header(HEADER_CACHE_CONTROL, cacheControl.toString())
                .build();
    };
}

OkHttpClient okHttpClient(Context context) {
    Cache cache = new Cache(context.getCacheDir(), cacheSize);

    return new OkHttpClient.Builder()
            .cache(cache)
            .addNetworkInterceptor(networkInterceptor())
            .build();
}

}

然后像这样创建API接口：

public interface ApiInterface {

    @GET("apiEndPoint")
    Call<ResponseBody> getData();
}

然后像这样在Activity 中使用RetrofitClient：

//Without Cache
Call<AboutResponse> call =
            RetrofitClient.getInstance(this)
                    .getApi()
                    .getAbout();

/With Cache
Call<AboutResponse> call =
            RetrofitClient.getInstance(this)
                    .getCachedApi()
                    .getAbout();

Answer 2

使用自定义注释

@Target(AnnotationTarget.FUNCTION)
@Retention(AnnotationRetention.RUNTIME)
annotation class Cacheable

class MainInterceptor : Interceptor {

    override fun intercept(chain: Interceptor.Chain): Response {
        val request = chain.request()
        val builder = request.newBuilder()
        request.tag(Invocation::class.java)?.let {
            if (!it.method().isAnnotationPresent(Cacheable::class.java)) {
                builder.cacheControl(CacheControl.Builder()
                    .noStore()
                    .build())
                return chain.proceed(builder.build())
            }
            try {
                builder.cacheControl(CacheControl.FORCE_NETWORK)
                return chain.proceed(builder.build())
            } catch (e: Throwable) {
                e.printStackTrace()
            }
            builder.cacheControl(CacheControl.Builder()
                .maxStale(Int.MAX_VALUE, TimeUnit.DAYS)
                .build())
        }
        return chain.proceed(builder.build())
    }
}


interface ServerApi {

    @Cacheable
    @GET("some_path")
    fun getSmth(): Call<ResponseBody>
}

给okhttp实例添加缓存不要丢了

OkHttpClient.Builder()
    .cache(Cache(context.cacheDir, 10 * 1024 * 1024L))
    .addInterceptor(MainInterceptor())
//...

Answer 3

caching (doc) 是 OkHttp 库，它主要由响应头驱动。您应该检查它们并验证 API 响应是否被缓存。 OkHttp logging interceptor 应该有助于调试。

要检查网络请求是否正在发生，请使用 HttpLoggingInterceptor 作为网络拦截器，而不是应用程序拦截器（请参阅https://github.com/square/okhttp/wiki/Interceptors）：

HttpLoggingInterceptor interceptor = HttpLoggingInterceptor();
interceptor.setLevel(Level.BASIC);
OkHttpClient client = new OkHttpClient.Builder()
.addNetworkInterceptor(new LoggingInterceptor())
.build();

当请求被缓存处理时，不会调用网络拦截器。

下一步将视情况而定。

1) 所有 API 请求都被缓存。

那么你应该能够为你不想缓存的方法使用注解@Headers("Cache-Control: no-cache")。

2) 不缓存所有 API 请求。

然后您可以更改您的 API（添加适当的缓存标头），也可以为 OkHttp 实施网络拦截器，该拦截器将修改响应（标头）。您可以在此回复中找到一些灵感：Can Retrofit with OKHttp use cache data when offline