code: private static void initJmxConn() throws IOException {
          if (jmxUrl != null) {
              JMXServiceURL url = new JMXServiceURL(jmxUrl);
              Map<String, String[]> env = null;
              if (jmxUsername != null) {
                  env = Maps.newHashMap();
                  String[] credentials = new String[]{jmxUsername, jmxPassword};
                  env.put(JMXConnector.CREDENTIALS, credentials);
              }
              JMXConnector jmxc = JMXConnectorFactory.connect(url, env);
              conn = jmxc.getMBeanServerConnection();
          }
      }
docs: 初始化jmx连接
  
  @throws IOException IOException