Android okhttp 获取缓存响应

Question

我不是处理 http 的专家，但我想完成的是：

如果响应在缓存中 return 如果不在缓存中 return 网络响应就这么简单。

但问题是响应代码始终是 504，但我确定它已被缓存，所以据我了解它应该 return != 504，代码在 "doGetRequest"方法。

我的 okhttp 客户端：

public class RestAsyncHttpClient {

/* Constants */
private static final String TAG = "RestAsyncHttpClient";
private static long HTTP_CACHE_SIZE = 10 * 1024 * 1024; // 10 MiB
private static final String DISK_CACHE_SUBDIR = "cacheApi";

/* Properties */
private static OkHttpClient mHttpClient;
private static Cache cache;
private static RestAsyncHttpClient instance = null;
private Context context;

public static RestAsyncHttpClient getInstance() {
    if (instance == null) {
        instance = new RestAsyncHttpClient();
    }
    return instance;
}

/**
 * Initialize HttpClient
 */
public void initialize(Context context) {
    setContext(context);

    mHttpClient = new OkHttpClient();

    configureSslSocketFactory();

    configureCache();

    configureTimeouts();
}

private void setContext(Context context) {
    this.context = context;
}

private void configureSslSocketFactory() {
    mHttpClient.setSslSocketFactory(HttpsURLConnection.getDefaultSSLSocketFactory());
}

public static void doGetRequest(String url, Callback callback) throws IOException {
    Request cachedRequest = new Request.Builder()
            .cacheControl(new CacheControl.Builder().onlyIfCached().build())
            .url(url)
            .build();
    Response forceCacheResponse = mHttpClient.newCall(cachedRequest).execute();
    if (forceCacheResponse.code() != 504) {
        // The resource was cached! Show it.
        callback.onResponse(forceCacheResponse);

    } else {
        Request networkRequest = new Request.Builder().url(url).build();
        mHttpClient.newCall(networkRequest).enqueue(callback);
    }
}

private void configureCache() {
    if (cache == null)
        cache = createHttpClientCache(context);

    mHttpClient.setCache(cache);
}

private static Cache createHttpClientCache(Context context) {
    try {
        File cacheDir = context.getDir("cache_api", Context.MODE_PRIVATE);
        return new Cache(cacheDir, HTTP_CACHE_SIZE);

    } catch (IOException exp) {
        LogHelper.error(TAG, "Couldn't create http cache because of IO problem.", exp);
        return null;
    }
}

private void configureTimeouts() {
    mHttpClient.setConnectTimeout(10, TimeUnit.SECONDS);
    mHttpClient.setWriteTimeout(35, TimeUnit.SECONDS);
    mHttpClient.setReadTimeout(35, TimeUnit.SECONDS);
}

}

我的缓存正在被填充，所以当没有可用连接时它应该从缓存中读取。

来自服务器的响应 Headers：

连接：关闭
Content-Type:application/json;字符集=iso-8859-1
日期：2015 年 3 月 23 日，星期一 11:04:44 GMT
服务器：Apache
Transfer-Encoding：分块
X-Powered-By:Servlet/2.5 JSP/2.1

请求Headers：

接受：text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,/;q=0.8
Accept-Encoding:gzip, deflate, sdch
Accept-Language:pt-PT,pt;q=0.8,en-US;q=0.6,en;q=0.4,fr;q=0.2
Cache-Control:max-age=0
连接：keep-alive
主持人：不能分享：448
User-Agent:Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 （KHTML，如 Gecko）Chrome/41.0.2272.101 Safari/537.36

Answer 1

当你得到响应时，你需要完整地读取它，否则它不会被缓存。这是因为 OkHttp 只有在你读完它的主体时才会将响应提交给缓存。

不需要 504 的特殊情况。只需定期发出请求，它会在可能的情况下使用缓存。

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