Android: WebView should InterceptRequest not add RequestProperties to WebView

Question

I intercept requests from webview using ifInterceptRequest

below is my code to return my WebResourceResponse

@TargetApi(Build.VERSION_CODES.LOLLIPOP) private static WebResourceResponse handleRequestViaUrlOnly(WebResourceRequest webResourceRequest){ String url = webResourceRequest.getUrl().toString(); Log.i("intercepting req....!!!", url); String ext = MimeTypeMap.getFileExtensionFromUrl(url); String mime = MimeTypeMap.getSingleton().getMimeTypeFromExtension(ext); try { HttpURLConnection conn = (HttpURLConnection) new URL(url).openConnection(); conn.setRequestProperty("Sample-Header", "hello"); conn.setDoOutput(true); conn.setDoInput(true); conn.setUseCaches(false); return new WebResourceResponse(mime, "UTF-8", conn.getInputStream()); } catch (IOException e) { e.printStackTrace(); } return null; } 

I call this method inside my CustomWebViewClient

 class CustomWebViewClient extends WebViewClient { @TargetApi(Build.VERSION_CODES.LOLLIPOP) @Override public WebResourceResponse shouldInterceptRequest(WebView view, WebResourceRequest request) { return handleRequestViaUrlOnly(request); } } 

However, when I check request headers from a remote WebView debugger in chrome: // checks for / # devices.

The additional RequestProperty that I added is missing.

 conn.setRequestProperty("Sample-Header", "hello"); 

The sample header is missing from the request headers in WebView.

Am I missing something? I would appreciate any help.

Answer 1

So the problem is that when you pass conn.getInputStream() , it only gives data. Response headers can be extracted using conn.getHeaderFields() . Also, you cannot return your additional header if the server does not support it and CORS is not involved. Here wireshark connection output

 GET /~fdc/sample.html HTTP/1.1 Sample-Header: hello Content-Type: application/x-www-form-urlencoded User-Agent: Dalvik/2.1.0 (Linux; U; Android 7.1; Android SDK built for x86_64 Build/NPF26K) Host: www.columbia.edu Connection: Keep-Alive Accept-Encoding: gzip Content-Length: 0 HTTP/1.1 200 OK Date: Wed, 01 Mar 2017 09:06:58 GMT Server: Apache Last-Modified: Thu, 22 Apr 2004 15:52:25 GMT Accept-Ranges: bytes Vary: Accept-Encoding,User-Agent Content-Encoding: gzip Content-Length: 8664 Keep-Alive: timeout=15, max=99 Connection: Keep-Alive Content-Type: text/html 

As you can see, the response does not have a Sample-Header: hello .

Here is simple code that will build WebResourceResponse headers from the response and add its own header to it:

 webView.setWebViewClient(new WebViewClient() { private Map<String, String> convertResponseHeaders(Map<String, List<String>> headers) { Map<String, String> responseHeaders = new HashMap<>(); responseHeaders.put("Sample-Header", "hello"); for (Map.Entry<String, List<String>> item : headers.entrySet()) { List<String> values = new ArrayList<String>(); for (String headerVal : item.getValue()) { values.add(headerVal); } String value = StringUtil.join(values, ","); Log.e(TAG, "processRequest: " + item.getKey() + " : " + value); responseHeaders.put(item.getKey(), value); } return responseHeaders; } @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP) @Override public WebResourceResponse shouldInterceptRequest(WebView view, WebResourceRequest request) { final String method = request.getMethod(); final String url = request.getUrl().toString(); Log.d(TAG, "processRequest: " + url + " method " + method); String ext = MimeTypeMap.getFileExtensionFromUrl(url); String mime = MimeTypeMap.getSingleton().getMimeTypeFromExtension(ext); try { HttpURLConnection conn = (HttpURLConnection)new URL(url).openConnection(); conn.setRequestMethod(method); conn.setRequestProperty("Sample-Header", "hello"); conn.setDoInput(true); conn.setUseCaches(false); Map<String, String> responseHeaders = convertResponseHeaders(conn.getHeaderFields()); responseHeaders.put("Sample-Header", "hello"); return new WebResourceResponse( mime, conn.getContentEncoding(), conn.getResponseCode(), conn.getResponseMessage(), responseHeaders, conn.getInputStream() ); } catch (Exception e) { Log.e(TAG, "shouldInterceptRequest: " + e); } return null; } });