java http请求

URL url = new URL(add_url);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setDoInput(true);
            connection.setDoOutput(true);
            connection.setRequestMethod("POST");
            connection.setUseCaches(false);
            connection.setInstanceFollowRedirects(true);
            // 传json时，需要这个，不传json，不需要
            connection.setRequestProperty("Content-Type", "application/json");
            connection.connect();
//            DataOutputStream out = new DataOutputStream(connection.getOutputStream());
            OutputStreamWriter out = new OutputStreamWriter(connection.getOutputStream(), "UTF-8");


            
            System.out.println(s5);
            out.write(s5);
            out.flush();
            out.close();

            BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
            String lines;
            StringBuffer sbf = new StringBuffer();
            while ((lines = reader.readLine()) != null)
            {
                lines = new String(lines.getBytes(), "utf-8");
                sbf.append(lines);
            }
            System.out.println(sbf);
            reader.close();
            // 断开连接
            connection.disconnect();