由於專案需要，需要用httpclient調其他部門的介面獲取資訊，學習了httpclient的使用方法，demo大概程式碼如下：

 public static List<Object> doPost(String url, JSONObject json, String infoname, Class cl){

        CloseableHttpClient httpclient = HttpClientBuilder.create().build();
        HttpPost post = new HttpPost(url);
        JSONObject response = null;
        List<Object> list=new ArrayList();
        try {
            StringEntity s = new StringEntity(json.toString());
            s.setContentEncoding("UTF-8");
            s.setContentType("application/json");//傳送json資料需要設定contentType
            post.setEntity(s);
            HttpResponse res = httpclient.execute(post);
            if(res.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
                String result = EntityUtils.toString(res.getEntity());// 返回json格式：
                System.out.println(result);
                response = JSONObject.parseObject(result);
                List<JSONObject> info = (List) response.get(infoname);

                for (JSONObject s1 : info) {
                    Object netDownData = (Object) JSONObject.toJavaObject(s1, cl);
                    list.add(netDownData);

                }

            }else{
                    logger.error("拉取失敗,錯誤編碼為："+res.getStatusLine().getStatusCode());
                }
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
        return list;
    }