URLConnection类

抽象类 URLConnection 是所有表示应用程序与 URL 之间通信链路的类的超类。该类的实例可以用来对由 URL 引用的资源进行读取和写入操作；
Java中的流分为两种，一种是字节流，另一种是字符流，字节流继承于抽象类inputStream/outputStream,字符流继承于抽象类Reader/Writer。Java中其他多种多样变化的流均是由它们派生出来的.

直接上例子。

public String Create (String token){ //token 是通过账号和密码取得的口令      map.put("roomName", aaa);      map.put("anchorPwd",bbb);      map.put("assistPwd", cccc);      map.put("userPwd",ddd);      String jsonObject = JSONObject.toJSONString(map);//将参数和值放到map里面，转为json字符串，作为参数传递      result = GotyeUtil.sendPost(url+"Create", jsonObject, token);      return   result;   //是一个json对象{ aaa:[],bbb:[]}public static String sendPost(String url, String param,String token) {    //PrintWriter out = null;    //需要用outputStreamWriter    OutputStreamWriter out=null;    BufferedReader in = null;      String result = "";      try {          URL realUrl = new URL(url);          //打开和URL之间的连接  调用URL对象openConnection()方法来创建URLConnection对象        URLConnection conn = realUrl.openConnection();          //设置通用的请求属性          conn.setRequestProperty("Accept", "application/json");          conn.setRequestProperty("connection", "Keep-Alive");          conn.setRequestProperty("user-agent","Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)");        conn.setRequestProperty("Content-Type", "application/json");        conn.setRequestProperty("Authorization", token);        //发送POST请求必须设置如下两行          conn.setDoOutput(true);          conn.setDoInput(true);          //获取URLConnection对象对应的输出流         out = new OutputStreamWriter(conn.getOutputStream(), "UTF-8");        //out = new PrintWriter(conn.getOutputStream());        //发送请求参数        out.append(param);        //out.print(param);        //flush输出流的缓冲          out.flush();          //定义BufferedReader输入流来读取URL的响应          in = new BufferedReader(              new InputStreamReader(conn.getInputStream(),"UTF-8"));        String line;          while ((line = in .readLine()) != null) {            result +=  line;        }      } catch (Exception e) {          System.out.println("发送POST请求出现异常！" + e);          e.printStackTrace();      }      //使用finally块来关闭输出流、输入流      finally {          try {              if (out != null) {                out.close();            }              if ( in != null) {                in .close();            }          } catch (IOException ex) {              ex.printStackTrace();          }      }      return result;  }