How to send requestparameter in POST request using HttpUrlConnection

问题

I need to send a POST request to a URL and send some request parameters. I am using HttpURLConnectionAPI for this. But my problem is I do not get any request parameter in the servlet. Although I see that the params are present in the request body, when I print the request body using request.getReader. Following is the client side code. Can any body please specify if this is correct way to send request parameters in POST request?

String urlstr = "http://serverAddress/webappname/TestServlet";

String params = "&paramname=paramvalue";

URL url = new URL(urlstr);

HttpURLConnection urlconn = (HttpURLConnection) url.openConnection();

urlconn.setDoInput(true);

urlconn.setDoOutput(true);

urlconn.setRequestMethod("POST");

urlconn.setRequestProperty("Content-Type", "text/xml");

urlconn.setRequestProperty("Content-Length", String.valueOf(params.getBytes().length));

urlconn.setRequestProperty("Content-Language", "en-US");

OutputStream os = urlconn.getOutputStream();

BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(os, "UTF-8"));

writer.write(params);

writer.close();

os.close();

回答1:

To be cleaner, you can encode to send the values.

String data = URLEncoder.encode("key1", "UTF-8") + "=" + URLEncoder.encode("value1", "UTF-8");
data += "&" + URLEncoder.encode("key2", "UTF-8") + "=" + URLEncoder.encode("value2", "UTF-8");

URL url = new URL("http://yourserver.com/whatever");
URLConnection conn = url.openConnection();
conn.setDoOutput(true);
OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
wr.write(data);

回答2:

Like @Kal said, get rid of the leading & and don't bother with the BufferedWriter. This works for me:

byte[] bytes = parameters.getBytes("UTF-8");
httpUrlConnection.setRequestProperty("Content-Length", String.valueOf(bytes.length));
httpUrlConnection.setRequestMethod("POST");
httpUrlConnection.setDoOutput(true);
httpUrlConnection.connect();
outputStream = httpUrlConnection.getOutputStream();
outputStream.write(bytes);

来源：https://stackoverflow.com/questions/5859667/how-to-send-requestparameter-in-post-request-using-httpurlconnection