UnknownHostException when downloading file

Question

I've been applying what seems to be simple solutions for this exception. I applied permissions in manifest and also use actual device and not an emulator.

This is :

    fileUrl = "http://xxx.xxx.xx.xx/resources/upload/pdfs/sample ははは.pdf";
    String urlLastPath = fileUrl.replaceFirst(".*/([^/?]+).*", "$1"); //urlLastPath = sample ははは.pdf

    String urlEncoded = URLEncoder.encode(urlLastPath, "utf-8"); //urlEncoded = sample %E3%81%AF%E3%81%AF%E3%81%AF.pdf

    File file = new File(fileUrl);
    String fileUrlRemains = file.getPath().replaceAll(file.getName(), ""); //fileUrlRemains = http://xxx.xxx.xx.xx/resources/upload/pdfs/

    String urlDecoded = null;
    if (urlEncoded.contains(" ")) {
        urlDecoded = urlEncoded.replaceAll(" ", "%20");
        urlStr = fileUrlRemains + urlDecoded;
    } else if (urlEncoded.contains("+")) {
        urlDecoded = urlEncoded.replaceAll(Pattern.quote("+"), "%20");
        urlStr = fileUrlRemains + urlDecoded;
    } else {
        urlStr = fileUrlRemains + urlEncoded;
    }

    URL url = new URL(urlStr); //urlStr is the complete file url(http://xxx.xxx.xx.xx/resources/upload/pdfs/sample%20%E3%81%AF%E3%81%AF%E3%81%AF.pdf)

    URLConnection conection = url.openConnection();
    conection.connect(); //This is where the exception points

    .
    .
    .

My manifest:

<uses-sdk
    android:minSdkVersion="11"
    android:targetSdkVersion="17" />

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.CALL_PHONE" />
<uses-permission android:name="android.permission.READ_PHONE_STATE" />

Not sure, but probably you should encode the URL. See [URL Encoding in Android](http://stackoverflow.com/questions/3286067/url-encoding-in-android) — Andrew T., Sep 04 '14 at 07:30
@AndrewT. I just edited my question, actually I already encoded the Japanese part. This worked before, I don't know what happened. — Compaq LE2202x, Sep 04 '14 at 08:07
Could you please try to access the URL (both non-encoded and encoded) from Android browser? Also, maybe from your PC browser to check if it can be accessed? — Andrew T., Sep 04 '14 at 08:46
@AndrewT. I tried in both platforms also both encoded and decoded, the URL was successfully downloaded. — Compaq LE2202x, Sep 04 '14 at 09:18
Umm, actually when I tried your code, `fileUrlRemains` becomes "http:\xxx.xxx.xx.xx\resources\upload\pdfs\" (note the single slash, not double slashes, http:\ ) — Andrew T., Sep 04 '14 at 09:27
@AndrewT. oh my gosh! I was even looking for my server folder's permissions. Okay, now that I know the cause I just have to find out which part it went wrong.. Thank you so much — Compaq LE2202x, Sep 04 '14 at 09:52

score 1 · Accepted Answer · answered Sep 04 '14 at 09:56

The problem is caused by invalid URL due to this line

String fileUrlRemains = file.getPath().replaceAll(file.getName(), "");
//expected: http://xxx.xxx.xx.xx/resources/upload/pdfs/
//actually: http:\xxx.xxx.xx.xx\resources\upload\pdfs\

Note the single slash caused by converting a URL to File.

I'm not sure what the RegEx does in the beginning, but here is a simpler approach to get both filename and the rest of the URL.

int i = fileUrl.lastIndexOf("/") + 1;
String urlLastPath = fileUrl.substring(i, fileUrl.length());
String fileUrlRemains = fileUrl.substring(0, i);

It will try to find the last slash, and "split" the URL accordingly.

UnknownHostException when downloading file

1 Answers1