What exactly does URLConnection.setDoOutput() affect?
You need to set it to true if you want to send (output) a request body, for example with POST or PUT requests. With GET, you do not usually send a body, so you do not need it.
Sending the request body itself is done via the connection's output stream:
conn.getOutputStream().write(someBytes);
setDoOutput(true) is used for POST and PUT requests. If it is false then it is for using GET requests.
Adding a comment, if you have a long lasting connection and you send both GETs and POSTs, this is what I do:
if (doGet) { // some boolean con.setDoOutput(false); // reset any previous setting, if con is long lasting con.setRequestMethod("GET");}else { con.setDoOutput(true); // reset any previous setting, if con is long lasting con.setRequestMethod("POST");}And to avoid making the connection long lasting, close it each time.
if (doClose) // some boolean con.setRequestProperty("Connection", "close");con.connect(); // force connect request