使用HttpURLConnection发送POST提交

        URL url = new URL("http://localhost:8080/TestClient/MyServlet");
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setDoInput(true);
        conn.setDoOutput(true);
        conn.setRequestMethod("POST");
        OutputStream outputStream = conn.getOutputStream();
        PrintWriter printWriter = new PrintWriter(outputStream);
        printWriter.print("username=zhangsan&password=123abc");
        printWriter.flush();
        printWriter.close();
        InputStream inputStream = conn.getInputStream();
        String string = IOUtils.toString(inputStream, "UTF-8");
        System.out.println(string);
        IOUtils.closeQuietly(printWriter);
        IOUtils.closeQuietly(inputStream);
        conn.disconnect();

        特别注意的是：printWriter写参数的时候别用println， 要是println的话就是最后一个参数加了回车换行。