如何异步调用WebViewClient.shouldInterceptRequest

Question

我想创建一个Intranet-Application.此应用程序将显示内容,通常只能在我们的内部环境中访问.例如http://intranet.ourfirm.com

现在我们可以从外部访问这些内容,例如https://ourproxy.com/ourIntranetApplicationID/ (这将被发送到http://intranet.ourfirm.com)

我将每个原始网址(如http://intranet.ourfirm.com/whatever/index.html)更改为 https://ourproxy.com/ourIntranetApplicationID/whatever/index.html.

在index.htm中,以绝对或相对方式定义了几个资源.我将它们全部变为绝对并将它们转换为我们的代理URL(请参阅*1)(可从我们公司外的任何地方访问)

这一切都很完美,但有一个大问题.它像地狱一样缓慢!转换过程在我的MyWebViewClient.shouldInterceptRequest方法中启动.

我的html有80个要加载的资源,并且为每个资源顺序调用shouldInterceptRequest:

public WebResourceResponse shouldInterceptRequest(WebView view, WebResourceRequest request) {
        LOGGER.debug("ENTER shouldInterceptRequest: " + String.format("%012d", interceptCounter.incrementAndGet()));
        WebResourceResponse response;


    HttpURLConnection conn;

        try {
            conn = myRewritingHelper.getConnection(request.getUrl(), method); // *1 this internally converts the url and gets a connection adds the header for Basic Auth etc.

            // add request headers
            for (Map.Entry<String, String> entry : request.getRequestHeaders().entrySet()) {
                conn.setRequestProperty(entry.getKey(), entry.getValue());
            }

            // Read input
            String charset = conn.getContentEncoding() != null ? conn.getContentEncoding() : Charset.defaultCharset().displayName();
            String mime = conn.getContentType();
            InputStream is = conn.getInputStream();



            long interceptStopTimestamp = System.currentTimeMillis();
            long durationIntercepting = interceptStopTimestamp - interceptStartTimestamp;
            LOGGER.info("InterceptionDuration : " + durationIntercepting);

            // *2 we have to define null for the mime-type , so the WebResourceResponse gets the type directly from the stream
            response = new WebResourceResponse(null, charset, isContents);
        } catch (IllegalStateException e) {
            LOGGER.warn("IllegalStateException", e);

        } catch (IOException e) {
            LOGGER.warn("IOException: Could not load resource: " + url, e);
        }


        LOGGER.debug("LEAVE shouldInterceptRequest: " + String.format("%012d", interceptCounter.get()));
        return response;
    }

如您所见,我在拦截方法的开头使用AtomicInteger递增和记录,并在方法结束时记录该值.

它始终记录:

ENTER shouldInterceptRequest:  000000000001
LEAVE shouldInterceptRequest:  000000000001
ENTER shouldInterceptRequest:  000000000002
LEAVE shouldInterceptRequest:  000000000002
ENTER shouldInterceptRequest:  000000000003
LEAVE shouldInterceptRequest:  000000000003
ENTER shouldInterceptRequest:  000000000004
LEAVE shouldInterceptRequest:  000000000004
:
:
ENTER shouldInterceptRequest:  000000000080
LEAVE shouldInterceptRequest:  000000000080

有了这个,我能够检查shouldInterceptRequest()方法永远不会异步获取startet.如果异步调用该方法,则会在前一个数字的LEAVE出现之前出现更大的数字@ ENTER- Comment.不幸的是,这从未发生过.

对myRewritingHelper.getConnection()的调用是非锁定的.

现在我的问题: 是否有可能激发WebviewClient异步调用其shouldInterceptRequest()方法？如果可以异步加载Web视图的多个资源,我很确定这会大大改善性能!Web视图按顺序加载资源.

一个有趣的子问题是,为什么我必须将Web资源创建中的mime-type定义为0(参见*2).像... response = new WebResourceResponse(mime,charset,isContents); ......不起作用.

谢谢你的任何有用的答案

编辑:

myRewritingHelper.getConnection(..)的方法很快,它只是打开与附加的http标头的连接:

private HttpURLConnection getConnection(String url, String httpMethod) throws MalformedURLException, IOException {

        String absoluteRewrittenUrl = urlConfigurationManager.getRewritedUrl(url); // this gets a rewritten url

        final HttpURLConnection connection = (HttpURLConnection) new URL(absoluteRewrittenUrl).openConnection();
        connection.setRequestMethod(httpMethod);
        connection.setConnectTimeout(CONNECTION_TIMEOUT_MS);
        connection.setReadTimeout(SOCKET_TIMEOUT_MS);
        connection.setRequestProperty("AUTHORIZATION",getBasicAuthentication());

        return connection;
    }

getConnection(..)方法只消耗几毫秒.

shouldInterceptRequest方法中的巨大"瓶颈"是注释//读取输入后的3个调用

String charset = conn.getContentEncoding() != null
conn.getContentEncoding():Charset.defaultCharset().displayName();
String mime = conn.getContentType();
InputStream is = conn.getInputStream();

这3个呼叫每次消耗最多2秒.因此,shouldInterceptRequestMethod()每次调用消耗超过2秒.(这就是我要求异步调用此方法的原因)

米哈伊尔·纳加诺夫建议做一个预取.任何人都可以展示如何预取并将数据正确地提供给WebResourceResponse的示例吗？

如果我使用真实的mime -type而不是null(参见*2)创建WebResourceResponse,则无法加载内容.html /文本将在WebView中显示为文本.

编辑2: 米哈伊尔的建议解决方案似乎是正确的解决方案.但不幸的是,它不是:

public class MyWebResourceResponse extends WebResourceResponse {
    private String url;
    private Context context;
    private MyResourceDownloader myResourceDownloader;
    private String method;
    private Map<String, String> requestHeaders;
    private MyWebViewListener myWebViewListener;
    private String predefinedEncoding;

public MyWebResourceResponse(Context context, String url, MyResourceDownloader myResourceDownloader, String method, Map<String, String> requestHeaders, MyWebViewListener myWebViewListener,String predefinedEncoding) {
        super("", "", null);
        this.url = url;
        this.context = context;
        this.myResourceDownloader = myResourceDownloader;
        this.method = method;
        this.requestHeaders = requestHeaders;
        this.myWebViewListener = myWebViewListener;
        this.predefinedEncoding = predefinedEncoding;
    }

    @Override
    public InputStream getData() {
        return new MyWebResourceInputStream(context, url, myResourceDownloader, method, requestHeaders, myWebViewListener);
    }

    @Override
    public String getEncoding() {
        if(predefinedEncoding!=null){
            return predefinedEncoding;
        }
        return super.getEncoding();
    }

    @Override
    public String getMimeType() {
        return super.getMimeType();
    }
}

MyWebResourceInputStream是这样的:

public class MyWebResourceInputStream extends InputStream {
    private static final Logger LOGGER = LoggerFactory.getLogger(MyWebResourceInputStream.class);
    public static final int NO_MORE_DATA = -1;
    private String url;
    private boolean initialized;
    private InputStream inputStream;
    private MyResourceDownloader myResourceDownloader;
    private String method;
    private Map<String, String> requestHeaders;
    private Context context;
    private MyWebViewListener myWebViewListener;

public MyWebResourceInputStream(Context context, String url, MyResourceDownloader myResourceDownloader,
            String method, Map<String, String> requestHeaders, MyWebViewListener myWebViewListener) {
        this.url = url;
        this.initialized = false;
        this.myResourceDownloader = myResourceDownloader;
        this.method = method;
        this.requestHeaders = requestHeaders;
        this.context = context;
        this.myWebViewListener = myWebViewListener;
    }
@Override
    public int read() throws IOException {
        if (!initialized && !MyWebViewClient.getReceived401()) {
            LOGGER.debug("- -> read ENTER *****");
            try {
                InterceptingHelper.InterceptingHelperResult result = InterceptingHelper.getStream(context, myResourceDownloader, url, method, requestHeaders, false);
                inputStream = result.getInputstream();
                initialized = true;
            } catch (final UnexpectedStatusCodeException e) {
                LOGGER.warn("UnexpectedStatusCodeException", e);
                if (e.getStatusCode() == HttpURLConnection.HTTP_UNAUTHORIZED) {
                    MyWebViewClient.setReceived401(true);
                    if (myWebViewListener != null) {
                        myWebViewListener.onReceivedUnexpectedStatusCode(e.getStatusCode());
                    }
                    LOGGER.warn("UnexpectedStatusCodeException received 401", e);
                }
            } catch (IllegalStateException e) {
                LOGGER.warn("IllegalStateException", e);
            }
        }
        if (inputStream != null && !MyWebViewClient.getReceived401()) {
            return inputStream.read();
        } else {
            return NO_MORE_DATA;
        }

    }
@Override
    public void close() throws IOException {
        if (inputStream != null) {
            inputStream.close();
        }
    }
@Override
    public long skip(long byteCount) throws IOException {
        long skipped = 0;
        if (inputStream != null) {
            skipped = inputStream.skip(byteCount);
        }
        return skipped;
    }
@Override
    public synchronized void reset() throws IOException {
        if (inputStream != null) {
            inputStream.reset();
        }
    }
@Override
    public int read(byte[] buffer) throws IOException {
        if (inputStream != null) {
            return inputStream.read(buffer);
        }
        return super.read(buffer);
    }
@Override
    public int read(byte[] buffer, int byteOffset, int byteCount) throws IOException {
        if (inputStream != null) {
            return inputStream.read(buffer, byteOffset, byteCount);
        }
        return super.read(buffer, byteOffset, byteCount);
    }
 public int available() throws IOException {
        if (inputStream != null) {
            return inputStream.available();
        }
        return super.available();
    }

public synchronized void mark(int readlimit) {
        if (inputStream != null) {
            inputStream.mark(readlimit);
        }
        super.mark(readlimit);
    }
 @Override
    public boolean markSupported() {
        if (inputStream != null) {
            return inputStream.markSupported();
        }
        return super.markSupported();
    }

呼叫始于

MyWebViewClient extends WebViewClient{

    public WebResourceResponse shouldInterceptRequest(WebView view, WebResourceRequest request){
    // a lot of other code
    String predefinedEncoding = getPredefinedEncodingFromUrl(url);
            return new MyWebResourceResponse(context, url, myResourceDownloader, method, requestHeaders, webViewListener, predefinedEncoding);
  }
}

它带来了性能提升,但它有一个巨大的缺点,即在创建MyWebResourceResponse类时没有定义编码.因为直到调用MyWebResourceInputStream.read()才建立连接.我发现webkit在getData()之前调用getEncoding(),当没有建立连接时,所以getEncoding始终为null.我开始使用预定义的编码定义一个变通方法(取决于url).但这远远不是通用解决方案!并且在每种情况下都不起作用有人知道替代解决方案吗？对不起米哈伊尔取消了接受的答案.

Answer 1

资源加载过程包括两个阶段:创建请求作业,然后运行它们以获取数据.shouldInterceptRequest在第一阶段调用,这些调用确实按顺序在单个线程上运行.但是当WebView的资源加载器接收到请求作业时,它会开始并行地从提供的流加载资源内容.

创建请求作业应该很快,并且它不应该成为瓶颈.您是否真的测量了shouldInterceptRequest完成所需的时间？

下一步是检查输入流是否实际上没有相互阻塞.此外,RewritingHelper是否预先获取内容,还是仅在读取流时按需加载它们？预取可以帮助提高加载速度.

至于mime类型 - 通常浏览器从响应头中获取它,这就是为什么需要通过WebResourceResponse构造函数提供它.我实际上不确定你的意思是"WebResourceResponse直接从流中获取类型"是什么意思 - 流只包含回复的数据,但不包含响应头.

UPDATE

所以,从您更新的问题看来,HttpURLConnection实际上是在内部加载资源shouldInterceptRequest,这就是为什么一切都这么慢.你需要做的是定义你自己的包装WebResourceResponse的类并且不对构造做任何事情,因此shouldInterceptRequest执行速度很快.实际装载应该在之后开始.

我找不到这个技术的很多好的代码示例,但是这个似乎或多或少地做了你需要的东西:https://github.com/mobilyzer/Mobilyzer/blob/master/Mobilyzer/src/com /mobilyzer/util/AndroidWebView.java#L252

通过预取我的意思是你可以在返回之后几乎立即开始加载数据shouldInterceptRequest,而不是等到WebView调用getData返回的方法WebResourceResponse.这样,您将在WebView询问时加载数据.

更新2

实际上,WebView中的一个问题是它在收到WebResourceResponsefrom 的实例后立即查询响应头shouldInterceptRequest.这意味着如果应用程序想要从网络本身加载资源(例如,用于修改它们),那么加载将永远不会像WebView本身加载这些资源那样快.

应用程序可以做的最好的方法是这样的(代码缺少正确的异常和错误处理,否则它会大3倍):

public WebResourceResponse shouldInterceptRequest(WebView view, final WebResourceRequest request) {
    final CountDownLatch haveHeaders = new CountDownLatch(1);
    final AtomicReference<Map<String, String>> headersRef = new AtomicReference<>();
    final CountDownLatch haveData = new CountDownLatch(1);
    final AtomicReference<InputStream> inputStreamRef = new AtomicReference<>();

    new Thread() {
        @Override
        public void run() {
            HttpURLConnection urlConnection =
                (HttpURLConnection) new URL(request.getUrl().toString()).openConnection();
            Map<String, List<String>> rawHeaders = urlConnection.getHeaderFields();
            // Copy headers from rawHeaders to headersRef
            haveHeaders.countDown();

            inputStreamRef.set(new BufferedInputStream(urlConnection.getInputStream()));
            haveData.countDown();
        }
    }.start();

    return new WebResourceResponse(
            null,
            "UTF-8",
            new InputStream() {
               @Override
               public int read() throws IOException {
                   haveInputStream.await(100, TimeUnit.SECONDS));
                   return inputStreamRef.get().read();
            }) {

        @Override
        public Map<String, String> getResponseHeaders() {
            haveHeaders.await(100, TimeUnit.SECONDS))
            return headersRef.get();
        }
    }
);