网络传输---HttpURLConnection

URL url = new URL(urlString);

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

//设置HttpURLConnection参数
            httpUrlConnection.setRequestMethod("POST");
            // 设置是否向httpUrlConnection输出，因为这个是post请求，参数要放在
            // http正文内，因此需要设为true, 默认情况下是false;
            httpUrlConnection.setDoOutput(true);
            // 设置是否从httpUrlConnection读入，默认情况下是true;
            httpUrlConnection.setDoInput(true);
            //设置不使用缓存
            httpUrlConnection.setUseCaches(false);
            //设置发送请求为utf-8
            httpUrlConnection.setRequestProperty("Content-type", "text/html;charset=utf-8");
            //设置网络请求时间最多为5秒；
            httpUrlConnection.setConnectTimeout(5000);
            //读取网页请求结果时间为15秒
            httpUrlConnection.setReadTimeout(25000);

// 连接，从上述url.openConnection()至此的配置必须要在connect之前完成，
            httpUrlConnection.connect();

//输出
            OutputStream out = httpUrlConnection.getOutputStream();
            //用到了缓存流,提高IO效率,由于数据为字符,用到字符转字节的包装流,并设置UTF-8编码
            BufferedWriter bout = new BufferedWriter(new OutputStreamWriter(out,"utf-8"));
            bout.write("demo");
            bout.flush();
            bout.close();

 //获得返回结果
            if (httpUrlConnection.getResponseCode() == httpUrlConnection.HTTP_OK) {//判断状态码是否为200
                    InputStream in = httpUrlConnection.getInputStream();
                    BufferedReader reader = new BufferedReader(new InputStreamReader(
                            in));
                    StringBuffer stringBuffer = new StringBuffer();
                    String str = "";
                    while ((str = reader.readLine()) != null) {
                            stringBuffer.append(str+"\n");
                    }
                    reader.close();
                    in.close();
                    return stringBuffer.toString();
            }else{
                    return null;
            }