code: public static String doPost(String url, Map<String, String> header, String param) throws KeyManagementException,
              NoSuchAlgorithmException, IOException {
  
          String result = null;
          HttpClient httpClient = new SSLClient();
          httpClient.getParams().setParameter(CoreConnectionPNames.CONNECTION_TIMEOUT, Constant.DEFAULT_CONN_TIMEOUT);
          httpClient.getParams().setParameter(CoreConnectionPNames.SO_TIMEOUT, Constant.DEFAULT_READ_TIMEOUT);
          HttpPost httpPost = new HttpPost(url);
          Iterator iterator;
          if (header != null) {
              Set<String> keys = header.keySet();
              iterator = keys.iterator();
  
              while(iterator.hasNext()) {
                  String key = (String)iterator.next();
                  httpPost.setHeader(key, header.get(key));
              }
          }
  
          httpPost.setEntity(new StringEntity(param, Constant.DEFAULT_CHARSET));
  
          HttpResponse response = httpClient.execute(httpPost);
  
          if (response != null) {
              HttpEntity resEntity = response.getEntity();
              if (resEntity != null) {
                  result = EntityUtils.toString(resEntity, Constant.DEFAULT_CHARSET);
              }
          }
  
          return result;
      }
docs: POST方式向Http(s)提交数据并获取返回结果
  
  @param url URL
  @param header Header
  @param param 参数（String）
  
  @return 服务器数据
  
  @throws KeyManagementException [ellipsis]
  @throws NoSuchAlgorithmException [ellipsis]
  @throws IOException [ellipsis]