android4.0 webkit 請求網絡數據的調用流程

1.
PassRefPtr<ResourceLoaderAndroid> ResourceLoaderAndroid::start(
        ResourceHandle* handle, const ResourceRequest& request, FrameLoaderClient* client, bool isMainResource, bool isSync)
{
    // Called on main thread
    FrameLoaderClientAndroid* clientAndroid = static_cast<FrameLoaderClientAndroid*>(client);
#if USE(CHROME_NETWORK_STACK)
    WebViewCore* webViewCore = WebViewCore::getWebViewCore(clientAndroid->getFrame()->view());
    bool isMainFrame = !(clientAndroid->getFrame()->tree() && clientAndroid->getFrame()->tree()->parent());
    return WebUrlLoader::start(client, handle, request, isMainResource, isMainFrame, isSync, webViewCore->webRequestContext());
#else
    return clientAndroid->webFrame()->startLoadingResource(handle, request, isMainResource, isSync);
#endif
}

2.

PassRefPtr<WebCore::ResourceLoaderAndroid>
WebFrame::startLoadingResource(WebCore::ResourceHandle* loader,
                                  const WebCore::ResourceRequest& request,
                                  bool mainResource,
                                  bool synchronous)
{
#ifdef ANDROID_INSTRUMENT
    TimeCounterAuto counter(TimeCounter::JavaCallbackTimeCounter);
#endif
    LOGV("::WebCore:: startLoadingResource(%p, %s)",
            loader, request.url().string().latin1().data());

    JNIEnv* env = getJNIEnv();
    AutoJObject javaFrame = mJavaFrame->frame(env);
    if (!javaFrame.get())
        return 0;

    WTF::String method = request.httpMethod();
    WebCore::HTTPHeaderMap headers = request.httpHeaderFields();

    WTF::String urlStr = request.url().string();
    int colon = urlStr.find(':');
    bool allLower = true;
    for (int index = 0; index < colon; index++) {
        UChar ch = urlStr[index];
        if (!WTF::isASCIIAlpha(ch))
            break;
        allLower &= WTF::isASCIILower(ch);
        if (index == colon - 1 && !allLower) {
            urlStr = urlStr.substring(0, colon).lower()
                    + urlStr.substring(colon);
        }
    }
    LOGV("%s lower=%s", __FUNCTION__, urlStr.latin1().data());
    jstring jUrlStr = wtfStringToJstring(env, urlStr);
    jstring jMethodStr = NULL;
    if (!method.isEmpty())
        jMethodStr = wtfStringToJstring(env, method);
    WebCore::FormData* formdata = request.httpBody();
    jbyteArray jPostDataStr = getPostData(request);
    jobject jHeaderMap = createJavaMapFromHTTPHeaders(env, headers);

    // Convert the WebCore Cache Policy to a WebView Cache Policy.
    int cacheMode = 0;  // WebSettings.LOAD_NORMAL
    switch (request.cachePolicy()) {
        case WebCore::ReloadIgnoringCacheData:
            cacheMode = 2; // WebSettings.LOAD_NO_CACHE
            break;
        case WebCore::ReturnCacheDataDontLoad:
            cacheMode = 3; // WebSettings.LOAD_CACHE_ONLY
            break;
        case WebCore::ReturnCacheDataElseLoad:
            cacheMode = 1;   // WebSettings.LOAD_CACHE_ELSE_NETWORK
            break;
        case WebCore::UseProtocolCachePolicy:
        default:
            break;
    }

    LOGV("::WebCore:: startLoadingResource %s with cacheMode %d", urlStr.ascii().data(), cacheMode);

    ResourceHandleInternal* loaderInternal = loader->getInternal();
    jstring jUsernameString = loaderInternal->m_user.isEmpty() ?
            NULL : wtfStringToJstring(env, loaderInternal->m_user);
    jstring jPasswordString = loaderInternal->m_pass.isEmpty() ?
            NULL : wtfStringToJstring(env, loaderInternal->m_pass);

    bool isUserGesture = UserGestureIndicator::processingUserGesture();
    jobject jLoadListener =
        env->CallObjectMethod(javaFrame.get(), mJavaFrame->mStartLoadingResource,
                (int)loader, jUrlStr, jMethodStr, jHeaderMap,
                jPostDataStr, formdata ? formdata->identifier(): 0,
                cacheMode, mainResource, isUserGesture,
                synchronous, jUsernameString, jPasswordString);

    env->DeleteLocalRef(jUrlStr);
    env->DeleteLocalRef(jMethodStr);
    env->DeleteLocalRef(jPostDataStr);
    env->DeleteLocalRef(jHeaderMap);
    env->DeleteLocalRef(jUsernameString);
    env->DeleteLocalRef(jPasswordString);
    if (checkException(env))
        return 0;

    PassRefPtr<WebCore::ResourceLoaderAndroid> h;
    if (jLoadListener)
        h = WebCoreResourceLoader::create(env, jLoadListener);
    env->DeleteLocalRef(jLoadListener);
    return h;
}

3.
    /**
     * Start loading a resource.
     * @param loaderHandle The native ResourceLoader that is the target of the
     *                     data.
     * @param url The url to load.
     * @param method The http method.
     * @param headers The http headers.
     * @param postData If the method is "POST" postData is sent as the request
     *                 body. Is null when empty.
     * @param postDataIdentifier If the post data contained form this is the form identifier, otherwise it is 0.
     * @param cacheMode The cache mode to use when loading this resource. See WebSettings.setCacheMode
     * @param mainResource True if the this resource is the main request, not a supporting resource
     * @param userGesture
     * @param synchronous True if the load is synchronous.
     * @return A newly created LoadListener object.
     */
    private LoadListener startLoadingResource(int loaderHandle,
                                              String url,
                                              String method,
                                              HashMap headers,
                                              byte[] postData,
                                              long postDataIdentifier,
                                              int cacheMode,
                                              boolean mainResource,
                                              boolean userGesture,
                                              boolean synchronous,
                                              String username,
                                              String password) {
        PerfChecker checker = new PerfChecker();

        if (mSettings.getCacheMode() != WebSettings.LOAD_DEFAULT) {
            cacheMode = mSettings.getCacheMode();
        }

        if (method.equals("POST")) {
            // Don't use the cache on POSTs when issuing a normal POST
            // request.
            if (cacheMode == WebSettings.LOAD_NORMAL) {
                cacheMode = WebSettings.LOAD_NO_CACHE;
            }
            String[] ret = getUsernamePassword();
            if (ret != null) {
                String domUsername = ret[0];
                String domPassword = ret[1];
                maybeSavePassword(postData, domUsername, domPassword);
            }
        }

        // is this resource the main-frame top-level page?
        boolean isMainFramePage = mIsMainFrame;

        if (DebugFlags.BROWSER_FRAME) {
            Log.v(LOGTAG, "startLoadingResource: url=" + url + ", method="
                    + method + ", postData=" + postData + ", isMainFramePage="
                    + isMainFramePage + ", mainResource=" + mainResource
                    + ", userGesture=" + userGesture);
        }

        // Create a LoadListener
        LoadListener loadListener = LoadListener.getLoadListener(mContext,
                this, url, loaderHandle, synchronous, isMainFramePage,
                mainResource, userGesture, postDataIdentifier, username, password);

        if (LoadListener.getNativeLoaderCount() > MAX_OUTSTANDING_REQUESTS) {
            // send an error message, so that loadListener can be deleted
            // after this is returned. This is important as LoadListener's
            // nativeError will remove the request from its DocLoader's request
            // list. But the set up is not done until this method is returned.
            loadListener.error(
                    android.net.http.EventHandler.ERROR, mContext.getString(
                            com.android.internal.R.string.httpErrorTooManyRequests));
            return loadListener;
        }

        // Note that we are intentionally skipping
        // inputStreamForAndroidResource.  This is so that FrameLoader will use
        // the various StreamLoader classes to handle assets.
        FrameLoader loader = new FrameLoader(loadListener, mSettings, method,
                mCallbackProxy.shouldInterceptRequest(url));
        loader.setHeaders(headers);
        loader.setPostData(postData);
        // Set the load mode to the mode used for the current page.
        // If WebKit wants validation, go to network directly.
        loader.setCacheMode(headers.containsKey("If-Modified-Since")
                || headers.containsKey("If-None-Match") ?
                        WebSettings.LOAD_NO_CACHE : cacheMode);
        // Set referrer to current URL?
        if (!loader.executeLoad()) {
            checker.responseAlert("startLoadingResource fail");
        }
        checker.responseAlert("startLoadingResource succeed");

        return !synchronous ? loadListener : null;
    }

4.

    /**
     * Issues the load request.
     *
     * Return value does not indicate if the load was successful or not. It
     * simply indicates that the load request is reasonable.
     *
     * @return true if the load is reasonable.
     */
    public boolean executeLoad() {
        String url = mListener.url();

        // Process intercepted requests first as they could be any url.
        if (mInterceptResponse != null) {
            if (mListener.isSynchronous()) {
                mInterceptResponse.loader(mListener).load();
            } else {
                WebViewWorker.getHandler().obtainMessage(
                        WebViewWorker.MSG_ADD_STREAMLOADER,
                        mInterceptResponse.loader(mListener)).sendToTarget();
            }
            return true;
        } else if (URLUtil.isNetworkUrl(url)){
            if (mSettings.getBlockNetworkLoads()) {
                mListener.error(EventHandler.ERROR_BAD_URL,
                        mListener.getContext().getString(
                                com.android.internal.R.string.httpErrorBadUrl));
                return false;
            }
            // Make sure the host part of the url is correctly
            // encoded before sending the request
            if (!URLUtil.verifyURLEncoding(mListener.host())) {
                mListener.error(EventHandler.ERROR_BAD_URL,
                        mListener.getContext().getString(
                        com.android.internal.R.string.httpErrorBadUrl));
                return false;
            }
            mNetwork = Network.getInstance(mListener.getContext());
            if (mListener.isSynchronous()) {
                return handleHTTPLoad();
            }
            WebViewWorker.getHandler().obtainMessage(
                    WebViewWorker.MSG_ADD_HTTPLOADER, this).sendToTarget();
            return true;
        } else if (handleLocalFile(url, mListener, mSettings)) {
            return true;
        }
        if (DebugFlags.FRAME_LOADER) {
            Log.v(LOGTAG, "FrameLoader.executeLoad: url protocol not supported:"
                    + mListener.url());
        }
        mListener.error(EventHandler.ERROR_UNSUPPORTED_SCHEME,
                mListener.getContext().getText(
                        com.android.internal.R.string.httpErrorUnsupportedScheme).toString());
        return false;

    }

5.

    boolean handleHTTPLoad() {
        if (mHeaders == null) {
            mHeaders = new HashMap<String, String>();
        }
        populateStaticHeaders();
        populateHeaders();

        // response was handled by Cache, don't issue HTTP request
        if (handleCache()) {
            // push the request data down to the LoadListener
            // as response from the cache could be a redirect
            // and we may need to initiate a network request if the cache
            // can't satisfy redirect URL
            mListener.setRequestData(mMethod, mHeaders, mPostData);
            return true;
        }

        if (DebugFlags.FRAME_LOADER) {
            Log.v(LOGTAG, "FrameLoader: http " + mMethod + " load for: "
                    + mListener.url());
        }

        boolean ret = false;
        int error = EventHandler.ERROR_UNSUPPORTED_SCHEME;
       
        try {
            ret = mNetwork.requestURL(mMethod, mHeaders,
                    mPostData, mListener);
        } catch (android.net.ParseException ex) {
            error = EventHandler.ERROR_BAD_URL;
        } catch (java.lang.RuntimeException ex) {
            /* probably an empty header set by javascript.  We want
               the same result as bad URL  */
            error = EventHandler.ERROR_BAD_URL;
        }
        if (!ret) {
            mListener.error(error, ErrorStrings.getString(error, mListener.getContext()));
            return false;
        }
        return true;
    }
6.

    /**
     * Request a url from either the network or the file system.
     * @param url The url to load.
     * @param method The http method.
     * @param headers The http headers.
     * @param postData The body of the request.
     * @param loader A LoadListener for receiving the results of the request.
     * @return True if the request was successfully queued.
     */
    public boolean requestURL(String method,
                              Map<String, String> headers,
                              byte [] postData,
                              LoadListener loader) {

        String url = loader.url();

        // Not a valid url, return false because we won't service the request!
        if (!URLUtil.isValidUrl(url)) {
            return false;
        }

        // asset, res, file system or data stream are handled in the other code
        // path. This only handles network request.
        if (URLUtil.isAssetUrl(url) || URLUtil.isResourceUrl(url)
                || URLUtil.isFileUrl(url) || URLUtil.isDataUrl(url)) {
            return false;
        }

        // If this is a prefetch, abort it if we're roaming.
        if (mRoaming && headers.containsKey("X-Moz") && "prefetch".equals(headers.get("X-Moz"))) {
            return false;
        }

        /* FIXME: this is lame.  Pass an InputStream in, rather than
           making this lame one here */
        InputStream bodyProvider = null;
        int bodyLength = 0;
        if (postData != null) {
            bodyLength = postData.length;
            bodyProvider = new ByteArrayInputStream(postData);
        }

        RequestQueue q = mRequestQueue;
        RequestHandle handle = null;
        if (loader.isSynchronous()) {
            handle = q.queueSynchronousRequest(url, loader.getWebAddress(),
                    method, headers, loader, bodyProvider, bodyLength);
            loader.attachRequestHandle(handle);
            handle.processRequest();
            loader.loadSynchronousMessages();
        } else {
            handle = q.queueRequest(url, loader.getWebAddress(), method,
                    headers, loader, bodyProvider, bodyLength);
            // FIXME: Although this is probably a rare condition, normal network
            // requests are processed in a separate thread. This means that it
            // is possible to process part of the request before setting the
            // request handle on the loader. We should probably refactor this to
            // ensure the handle is attached before processing begins.
            loader.attachRequestHandle(handle);
        }

        return true;
    }
作者：lihui130135