public class HttpClientUtil {

    private static final String CONTENT_TYPE_TEXT_JSON = "text/json";

    private static final String APPLICATION_JSON = "application/json";

 public static String postJson(String url, String json) {

        CloseableHttpClient httpclient = HttpClients.createDefault();

        HttpPost httppost = new HttpPost(url);

        httppost.addHeader(HTTP.CONTENT_TYPE, APPLICATION_JSON);

        try {

            StringEntity se = new StringEntity(json);

            se.setContentType(CONTENT_TYPE_TEXT_JSON);

            se.setContentEncoding(new BasicHeader(HTTP.CONTENT_TYPE, APPLICATION_JSON));

            httppost.setEntity(se);

            CloseableHttpResponse response = httpclient.execute(httppost);

            try {

                HttpEntity entity = response.getEntity();

                if (entity != null) {

                    return EntityUtils.toString(entity, "UTF-8");

                }

            } finally {

                response.close();

            }

        } catch (ClientProtocolException e) {

            e.printStackTrace();

        } catch (UnsupportedEncodingException e1) {

            e1.printStackTrace();

        } catch (IOException e) {

            e.printStackTrace();

        } finally {

            // 关闭连接,释放资源

            try {

                httpclient.close();

            } catch (IOException e) {

                e.printStackTrace();

            }

        }

        return "";

    }

}