URLConnection returning empty inputStream

Question

I am trying to fetch input stream pdf from URL Connection but I am getting an empty input stream. Can anyone please tell me what is I am doing wrong? Following is the code:

<!-- language: java -->

URL fileUrl = new URL("https://www.dropbox.com/s/ao3up7xudju4qm0/Amalgabond%20Adhesive%20Agent.pdf");
HttpURLConnection connection = (HttpURLConnection)fileUrl.openConnection();
connection.connect(); 
InputStream is = connection.getInputStream();
Log.i("TAG", "is.available(): " + is.available());

is.available() is returning 0 empty stream.

I am stuck at this. I dont know Why I am getting `0` or sometimes `1` — Mustansar Saeed, Apr 18 '14 at 20:06
Yes browser is showing the pdf file with this url `https://www.dropbox.com/s/ao3up7xudju4qm0/Amalgabond%20Adhesive%20Agent.pdf` — Mustansar Saeed, Apr 18 '14 at 20:08
The only difference with your snippet, is that I changed the last line for : `System.out.println("is.available(): " + is.available());` — slaadvak, Apr 18 '14 at 20:13
I am using Windows 8 ... Is there any `url encoding required`? becuase file name has `spaces` are these any issues? — Mustansar Saeed, Apr 18 '14 at 20:17
let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/50988/discussion-between-slaadvak-and-mustang) — slaadvak, Apr 18 '14 at 20:18
Related: https://stackoverflow.com/questions/3695372/what-does-inputstream-available-do-in-java/3695378 — AlikElzin-kilaka, Jan 20 '19 at 12:41

score 3 · Answer 1 · answered Apr 18 '14 at 20:26

3

According to the javadoc, available() does not block and wait until all data is available, so you might have not completely received your stuff when its called.

You should use something like this instead of available() :

int bytesRead;
byte[] buffer = new byte[100000];

while((bytesRead = is.read(buffer)) > 0){

    // Do something here with buffer
}

read() is a blocking method.

answered Apr 18 '14 at 20:26

slaadvak

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How to print the contents using this buffer? – Mustansar Saeed Apr 18 '14 at 20:37
If you want to print text, you can do it with a scanner instead : http://stackoverflow.com/a/5445161/3183264 – slaadvak Apr 18 '14 at 20:39
Why you were getting bytes when you did `is.available()`? – Mustansar Saeed Apr 18 '14 at 20:45
Maybe, because my Internet connection has less latency than yours, so more bytes where read from the stream when I was calling `available()`. – slaadvak Apr 18 '14 at 20:47
@slaadvak It's a PDF. You can't use a Scanner on that. – user207421 Apr 18 '14 at 23:51
You're right. But in this case, the page retrieved is in fact a Web page showing the pdf file. It's HTML, not a binary PDF. – slaadvak Apr 19 '14 at 01:13
You can't realistically use a Scanner on an HTML page either. You need an HTML parser. – user207421 Apr 19 '14 at 02:25

score 0 · Answer 2 · answered Apr 18 '14 at 23:10

0

You're misusing the available() method. It doesn't tell you the length of the input stream, so the fact that it returns zero doesn't indicate that it's empty. See the Javadoc, where all this is explicitly stated.

Just read it until end of stream.

answered Apr 18 '14 at 23:10

user207421

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score 0 · Answer 3 · edited May 23 '17 at 12:29

0

If your ultimate goal is to download a file from Dropbox, you should use the Dropbox Java API, or maybe this simpler solution. Otherwise, a URLConnection to a file on Dropbox will download a web page (in HTML) showing you a link to click (with a lot of other stuff !) for downloading your file.

edited May 23 '17 at 12:29

Community

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answered Apr 19 '14 at 01:35

slaadvak

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I do not want to download the file. I just want to open it, retrieve `inputstream` and fetch bytes from it. – Mustansar Saeed Apr 19 '14 at 05:19

URLConnection returning empty inputStream

3 Answers3