android網路開源架構volley(五)——volley的一些細節

標籤：android   volley   delete   http   

    最近又把volley拿出來整理了下。之前沒有遇到過的一些小問題又來了，在此記錄下：

1、HttpUrlConnection DELETE 方式無法添加body的問題：java.net.ProtocolException: DELETE does not support writing

    這個可以算是一個系統級的bug，為什麼這麼說，請看這裡，這個問題在java8中才得以解決。沒辦法直接過去，咱就繞過去。查看HttpUrlConnection，我們發現他是一個抽象類別，因此可以試試能不能通過它的其他實現來達到我們的目的。最終我們決定使用okhttp這個實現。地址為：https://github.com/square/okhttp。

接著我們還得去看看volley的源碼，由於我們的app相容的最低版本是4.0，因此我們知道最終調用的是HurlStack：

    public static RequestQueue newRequestQueue(Context context, HttpStack stack) {...        if (stack == null) {            if (Build.VERSION.SDK_INT >= 9) {                stack = new HurlStack();            } else {                // Prior to Gingerbread, HttpUrlConnection was unreliable.                // See: http://android-developers.blogspot.com/2011/09/androids-http-clients.html                stack = new HttpClientStack(AndroidHttpClient.newInstance(userAgent));            }        }...    }

因此我們只需要將HurlStack的相關代碼修改即可，如下：

volley.java

public static RequestQueue newRequestQueue(Context context, HttpStack stack) {...        if (stack == null) {            if (Build.VERSION.SDK_INT >= 9) {                // old way: stack = new HurlStack();            // http://square.github.io/okhttp/                stack = new HurlStack(null, null, new OkUrlFactory(new OkHttpClient()));            } else {                // Prior to Gingerbread, HttpUrlConnection was unreliable.                // See: http://android-developers.blogspot.com/2011/09/androids-http-clients.html                stack = new HttpClientStack(AndroidHttpClient.newInstance(userAgent));            }        }...    }

HurlStack.java

/** * An {@link HttpStack} based on {@link HttpURLConnection}. */public class HurlStack implements HttpStack {    private final OkUrlFactory mOkUrlFactory;     /**     * @param urlRewriter Rewriter to use for request URLs     * @param sslSocketFactory SSL factory to use for HTTPS connections     * @param okUrlFactory solution delete body(https://github.com/square/okhttp)     */    public HurlStack(UrlRewriter urlRewriter, SSLSocketFactory sslSocketFactory, OkUrlFactory okUrlFactory) {        mUrlRewriter = urlRewriter;        mSslSocketFactory = sslSocketFactory;        mOkUrlFactory = okUrlFactory;    }    /**     * Create an {@link HttpURLConnection} for the specified {@code url}.     */    protected HttpURLConnection createConnection(URL url) throws IOException {if(null != mOkUrlFactory){return mOkUrlFactory.open(url);}        return (HttpURLConnection) url.openConnection();    }    @SuppressWarnings("deprecation")    /* package */     static void setConnectionParametersForRequest(HttpURLConnection connection,            Request<?> request) throws IOException, AuthFailureError {        switch (request.getMethod()) {            ...            case Method.DELETE:                connection.setRequestMethod("DELETE");                addBodyIfExists(connection, request);                break;            ...            default:                throw new IllegalStateException("Unknown method type.");        }    }...}

2、關於（修改）volley的緩衝

    volley有完整的一套緩衝機制。而目前我們想做個簡單的需求：部分介面（幾乎不會改動的）簡單的做一定時間的緩衝，研究了下代碼發現很容易修改達到自己的目的（有時間在分析下volley的緩衝機制，這個一定要做）。簡單來說修改一個地方：request.parseNetworkResponse中的

HttpHeaderParser（此處突然感慨volley的設計TMD靈活了，想怎麼改就怎麼改）。HttpHeaderParser修改後的代碼如下：

/** * 修改後的，使用者處理緩衝 */public class BHHttpHeaderParser {    /**     * Extracts a {@link Cache.Entry} from a {@link NetworkResponse}.     *     * @param response The network response to parse headers from     * @return a cache entry for the given response, or null if the response is not cacheable.     */    public static Cache.Entry parseCacheHeaders(NetworkResponse response, boolean isCustomCache) {...        if(isCustomCache){        softExpire = now + Config.HTTP_CACHE_TTL;        } else {        if (hasCacheControl) {            softExpire = now + maxAge * 1000;        } else if (serverDate > 0 && serverExpires >= serverDate) {            // Default semantic for Expire header in HTTP specification is softExpire.            softExpire = now + (serverExpires - serverDate);        }        }                Cache.Entry entry = new Cache.Entry();        entry.data = response.data;        entry.etag = serverEtag;        entry.softTtl = softExpire;        entry.ttl = entry.softTtl;        entry.serverDate = serverDate;        entry.responseHeaders = headers;        return entry;    }...}

此處大家可以發現，我們主要是根據自訂的變數決定如何修改cache的TTL來達到自己的目的。

以後有其他關於volley的總結都記錄在此。

android網路開源架構volley(五)——volley的一些細節