code: public static String doPost(String url, String ctype, byte[] content, int connectTimeout,
                                  int readTimeout, String proxyHost, int proxyPort) throws IOException {
          HttpURLConnection conn = null;
          OutputStream out = null;
          String rsp = null;
          try {
              try {
                  conn = null;
                  if (!StringUtils.isEmpty(proxyHost)) {
                      conn = getConnection(new URL(url), METHOD_POST, ctype, proxyHost, proxyPort);
                  } else {
                      conn = getConnection(new URL(url), METHOD_POST, ctype);
                  }
                  conn.setConnectTimeout(connectTimeout);
                  conn.setReadTimeout(readTimeout);
              } catch (IOException e) {
                  Map<String, String> map = getParamsFromUrl(url);
                  AlipayLogger.logCommError(e, url, map.get("app_key"), map.get("method"), content);
                  throw e;
              }
              try {
                  out = conn.getOutputStream();
                  out.write(content);
                  rsp = getResponseAsString(conn);
              } catch (IOException e) {
                  Map<String, String> map = getParamsFromUrl(url);
                  AlipayLogger.logCommError(e, conn, map.get("app_key"), map.get("method"), content);
                  throw e;
              }
  
          } finally {
              if (out != null) {
                  out.close();
              }
              if (conn != null) {
                  conn.disconnect();
  
              }
          }
  
          return rsp;
      }
docs: 执行HTTP POST请求。
  
  @param url 请求地址
  @param ctype 请求类型
  @param content 请求字节数组
  @param connectTimeout 连接超时时间
  @param readTimeout 请求超时时间
  @param proxyHost 代理host，传null表示不使用代理
  @param proxyPort 代理端口，传0表示不使用代理
  @return 响应字符串
  @throws IOException