为啥我这里取了流根本拿不到数据啊，求解答

我是想从外部接口那里通过流的方式拿到我想要的数据，这个url在测试工具上是可以拿得到对应数据的，但是在流里面就为null了，求解，是不是用流取这种思路不对啊，我是从这篇文章那里借鉴的https://blog.csdn.net/myme95/article/details/89359677?spm=1001.2101.3001.6650.7&utm_medium=distribute.pc_relevant.none-task-blog-2%7Edefault%7EBlogCommendFromBaidu%7ERate-7.pc_relevant_default&depth_1-utm_source=distribute.pc_relevant.none-task-blog-2%7Edefault%7EBlogCommendFromBaidu%7ERate-7.pc_relevant_default&utm_relevant_index=14

运行结果及报错内容

我的解答思路和尝试过的方法

我想要达到的结果

你这个肯定不行啊，你要用springboot发请求，要用resttemple

    public static Map<String, String> httpPost(String url, String param, Map<String, String> headers, ContentType contentType) {
        HttpPost httpPost = new HttpPost(url);
        CloseableHttpResponse response = null;
        Map<String, String> result = new HashMap<>();
        try {
            // 设置header
            if (headers != null) {
                for (Entry<String, String> entry : headers.entrySet()) {
                    httpPost.setHeader(entry.getKey(), entry.getValue());
                }
            }

            StringEntity paramEntity = new StringEntity(param, contentType);
            httpPost.setEntity(paramEntity);
            response = httpClient.execute(httpPost);
            result = getResult(response);
        } catch (IOException e) {
            log.error("http请求异常，{}", url, e);
        } finally {
            try {
                if (response != null) {
                    response.close();
                }
            } catch (IOException e) {
                log.error("response.close失败", e);
            }
        }
        return result;
    }

    /**
     * 获取Response返回结果
     *
     * @param response
     * @return
     * @throws IOException
     */
    private static Map<String, String> getResult(CloseableHttpResponse response) throws IOException {
        Map<String, String> result = new HashMap<>();
        String statusCode = response.getStatusLine().getStatusCode() + "";
        HttpEntity entity = response.getEntity();
        if (entity != null) {
            String content = EntityUtils.toString(entity, CHARSET);
            result.put(CONTENT, content);
            result.put(STATUSCODE, statusCode);
        }
        return result;
    }

   public static final String CONTENT = "content";
    public static final String STATUSCODE = "statusCode";

    private static final String CHARSET = "UTF-8";