My code is like the following:
URLConnection cnx = address.openConnection();
cnx.setAllowUserInteraction(false);
cnx.setDoOutput(true);
cnx.addRequestProperty("User-Agent",
"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0)");
InputStream is = cnx.getInputStream();
Is it ok if I set the headers before I get the InputStream? Will my header be sent, or will the server see the default URLConnection's user-agent ( if any ) ?
The headers must be set prior to getting the InputStream to have any affect - an IllegalStateException will be thrown if the connection is already open.
As far as the User-Agent header specifically, it should be sent if it has been set.
See the URLConnection JavaDoc.
To answer the question, the code is correct. The moment getInputStream(), an HTTP get is sent to the target server.
A side-note on user-agent, if you don't set it, URLConnection will send the default one anyway, which is:
User-Agent: Java/1.6.0_24 (varies depending on your java version)
I'd advise against using low-level constructs such as URLConnection. There are plenty of libraries for sending HTTP requests, with the most prominent being Apache HTTP Client.
