发送 Java POST 请求而不调用 getInputStream()

Question

I would like to send a POST request in Java. At the moment, I do it like this:

URL url = new URL("myurl");
URLConnection con = url.openConnection();
con.setDoOutput(true);
PrintStream ps = new PrintStream(con.getOutputStream());
ps.println("key=" + URLEncoder.encode("value"));
// we have to get the input stream in order to actually send the request
con.getInputStream();  
ps.close();

I do not understand why I have to call con.getInputStream() in order to actually send the request. If I do not call it, the request is not sent.

Is there a problem using PrintStream? It should not matter if I take a PrintStream, PrintWriter or something else, right?

Answer 1

I think this is the easiest way.

con.setDoOutput(true);
PrintStream ps = new PrintStream(con.getOutputStream());
ps.print("&client_id="+ 2);
ps.print("&amount="+10);
ps.flush();
ps.close();

Answer 2

URL represents some source.

URLConnection represents a connection to the resource.

you need call connection.connect() to connect the connection

Answer 3

Try to add

con.setDoInput (false);

before writing to the output.

PS: and you should also call con.connect () as swanliu says.

This is what I came up with

 private static final void sendPostRequest (final String urlAddress, String key, String value) throws Exception { URL url = new URL (urlAddress); URLConnection con = url.openConnection (); con.setDoOutput (true); con.setDoInput (false); PrintStream ps = new PrintStream (con.getOutputStream ()); ps.println (key + "=" + URLEncoder.encode (value, "UTF-8")); ps.flush (); con.connect (); ps.close (); } 

I checked with WireShark that a tcp connection is being established and that closed. But don't know how check that the server received the request. If you have a quick way to check it you may try that code.

Answer 4

I think a post of another thread answered my question. Sorry, but I found it too late. You can find it here .

PS: Unfortunately, Stackoverflow added my last answer to the question as a comment, because my answer was too short. And it is not possible to mark a comment as the correct answer... Hope this one is long enough :-)