我正在尝试使用Retrofit & OKHttp来缓存HTTP响应。我关注了this gist,最后得到了下面的代码:
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);
这是带有缓存控制标头的MyApi
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,我在线请求并检查缓存文件。正确的JSON响应和标头都在那里。但是当我尝试离线请求时,我总是得到RetrofitError UnknownHostException
。要使Retrofit从缓存中读取响应,我还需要做什么吗?
编辑:由于OKHttp 2.0.x HttpResponseCache
为Cache
,setResponseCache
为setCache
发布于 2014-05-07 03:56:40
2.x版本的编辑:
OkHttp拦截器是脱机时访问缓存的正确方式:
1)创建Interceptor:
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)设置客户端:
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)添加要改造的客户端
Retrofit retrofit = new Retrofit.Builder()
.baseUrl(BASE_URL)
.client(client)
.addConverterFactory(GsonConverterFactory.create())
.build();
同时检查@kosiara - Bartosz Kosarzycki的answer,你可能需要从响应中删除一些头部。
OKHttp 2.0.x (检查原始答案):
由于OKHttp 2.0.x HttpResponseCache
为Cache
,因此setResponseCache
为setCache
。所以你应该像这样使用setCache
:
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);
原始答案:
事实证明,要使OkClient
从缓存中读取,服务器响应必须具有Cache-Control: public
。
此外,如果您想从网络请求,当可用时,您应该添加Cache-Control: max-age=0
请求头。This answer展示了如何将其参数化。我是这样使用它的:
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);
}
}
});
发布于 2015-12-14 19:34:17
上面所有的方法对我都不起作用。我尝试在 2.0.0-beta2中实现离线缓存。我使用okHttpClient.networkInterceptors()
方法添加了一个拦截器,但在尝试脱机使用缓存时收到了java.net.UnknownHostException
。事实证明,我还必须添加okHttpClient.interceptors()
。
问题是缓存没有写入闪存,因为服务器返回了阻止OkHttp存储响应的Pragma:no-cache
。即使在修改请求标头值之后,脱机缓存也不起作用。经过反复试验,我通过从响应中删除杂注而不是从request - response.newBuilder().removeHeader("Pragma");
中删除杂注,在不修改后端的情况下让缓存正常工作
升级:2.0.0-beta2;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();
}
发布于 2016-04-22 21:28:47
我的解决方案是:
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();
}
https://stackoverflow.com/questions/23429046
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