java 发送数据代码 java发送httppost请求

public static String doPost(String URL, String jsonStr){
        OutputStreamWriter out = null;
        BufferedReader in = null;
        StringBuilder result = new StringBuilder();
        HttpURLConnection conn = null;
        try{
            java.net.URL url = new URL(URL);
            conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("POST");
            //发送POST请求必须设置为true
            conn.setDoOutput(true);
            conn.setDoInput(true);
            //设置连接超时时间和读取超时时间
            conn.setConnectTimeout(30000);
            conn.setReadTimeout(10000);
            conn.setRequestProperty("Content-Type", "application/json");
            conn.setRequestProperty("Accept", "application/json");
            //获取输出流
            out = new OutputStreamWriter(conn.getOutputStream());

            out.write(jsonStr);
            out.flush();
            out.close();
            //取得输入流，并使用Reader读取
            if (200 == conn.getResponseCode()){
                in = new BufferedReader(new InputStreamReader(conn.getInputStream(), "UTF-8"));
                String line;
                while ((line = in.readLine()) != null){
                    result.append(line);
                    
                }
            }else{   
            System.out.println("出错了");           
                return "";
            }
        }catch (Exception e){
            e.printStackTrace();
            return "";
        }finally {
            try{
                if(out != null){
                    out.close();
                }
                if(in != null){
                    in.close();
                }
            }catch (IOException ioe){
                ioe.printStackTrace();
            }
        }
        return result.toString();

    }