为什么java没有读取Content-length响应头？

Question

I have the following code to read the content-length response header of the resource pointed by the following url but this code doesn't read the content length and returns -1. I am wondering why.

 try{


String song_url = "https://doc-0c-6o-docs.googleusercontent.com/docs/securesc/mtop3kcd4g9holc81thpce8mmck772ja/10to2su90o897bl390ojai9srph2fmvq/1407182400000/15635312626103908265/15635312626103908265/0B8CobC-HnuclMm5sUnVpOW13eEk?e=download&h=16653014193614665626&nonce=5beqd4pl58o30&user=15635312626103908265&hash=qbqjjhkrpco10b8ggu7ko5qa5c64th2m";


                    URL web = new URL(song_url);

                    con1 = web.openConnection();

                     total_size = con1.getContentLength();

                    ((HttpURLConnection)con1).disconnect();

                    return total_size;

                }
                catch(Exception e){

                    e.printStackTrace();
                }

                ((HttpURLConnection)con1).disconnect();

Now, the strange thing is if you just paste this url in the browser

https://doc-0c-6o-docs.googleusercontent.com/docs/securesc/mtop3kcd4g9holc81thpce8mmck772ja/10to2su90o897bl390ojai9srph2fmvq/1407182400000/15635312626103908265/15635312626103908265/0B8CobC-HnuclMm5sUnVpOW13eEk?e=download&h=16653014193614665626&nonce=5beqd4pl58o30&user=15635312626103908265&hash=qbqjjhkrpco10b8ggu7ko5qa5c64th2m

and then under inspect element > network in google chrome then you will see that the browser reads the content length correctly.

content-length:79476777

But why is the java code failing to read the content-length? Is this a problem with the library i am using? Thanks for the help!

Answer 1

That would be because the server isn't sending a Content-length header. There are a least two other ways it can convey the length:

1. By closing the socket after sending the request body. In HTTP 1.1 I think this would have to be accompanied by a 'Connection: close ' header. In this case the content length is the length of the body, and you have to read it all to measure it.

2. By using chunked transfer encoding. In this case the content length is the sum of the lengths of the chunks. Again you would have to read it all to determine the length.