public Object getAttribute(ObjectName objName, String attrName) throws Exception {
        return mbeanServerConnection.getAttribute(objName, attrName);
    }
get the monitor object of the object name and attribute name. See
{@link org.ngrinder.monitor.domain.MonitorCollectionInfoDomain}.

@param objName  is the object name of the object in JMX MBean server.
@param attrName is the attribute name
@return the monitor object from MBean
@throws Exception wraps all JMX related exception
ngrinder-core/src/main/java/org/ngrinder/monitor/share/domain/MBeanClient.java