Android get file length via HttpConnection

Question

I'm trying to develop simple android download manager, in this library i get file length from http connection via two method as this code:

String contentLength = httpConnection.getHeaderField("Content-Length");
if (TextUtils.isEmpty(contentLength) || contentLength.equals("0") || contentLength.equals("-1")) {
    length = httpConnection.getContentLength();
} else {
    length = Long.parseLong(contentLength);
}

this code work fine when i get 206 on

httpConnection.getResponseCode();

but when i get 200 and

if (TextUtils.isEmpty(contentLength) || contentLength.equals("0") || contentLength.equals("-1")) {

is false

httpConnection.getContentLength();

return 0

full this part of my code:

try {
    httpConnection = (HttpURLConnection) url.openConnection();
    httpConnection.setConnectTimeout(Constants.HTTP.CONNECT_TIME_OUT);
    httpConnection.setReadTimeout(Constants.HTTP.READ_TIME_OUT);
    httpConnection.setRequestMethod(Constants.HTTP.GET);
    httpConnection.setRequestProperty("Range", "bytes=" + 0 + "-");
    final int responseCode = httpConnection.getResponseCode();
    if (responseCode == HttpURLConnection.HTTP_OK) {
        parseResponse(httpConnection, false);
    } else if (responseCode == HttpURLConnection.HTTP_PARTIAL) {
        parseResponse(httpConnection, true);
    } else {
        throw new DownloadException(DownloadStatus.STATUS_FAILED, "UnSupported response code:" + responseCode);
    }
} catch (ProtocolException e) {
    throw new DownloadException(DownloadStatus.STATUS_FAILED, "Protocol error", e);
} catch (IOException e) {
    throw new DownloadException(DownloadStatus.STATUS_FAILED, "IO error", e);
} finally {
    if (httpConnection != null) {
        httpConnection.disconnect();
    }
}

this is my testing link to download and get file length

http://wallpaperwarrior.com/wp-content/uploads/2016/09/Wallpaper-16.jpg

Answer 1

When you are getting 200 (OK) instead of 206 (Partial Content), your Range Retrieval Requests is not satisfied.

From W3 docs :

• The presence of a Range header in an unconditional GET modifies what is returned if the GET is otherwise successful. In other words, the response carries a status code of 206 (Partial Content) instead of 200 (OK).

More details : https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.35.2

You must check server-side logs to know the reason behind its failure.

Edit1

When you are getting 200 (OK), check for Accept-Ranges: bytes header in Response header. Accept-Ranges response header indicates that the server has range header support.

Check here the exchange of Request-Response between Chrome and a static web server explained by johnstok.