code: String getDefaultSourcClassForSystemEvent(Class systemEventClass)
      {
          Constructor[] constructors = systemEventClass.getConstructors();
          for (Constructor constr : constructors)
          {
              Class[] parms = constr.getParameterTypes();
              if (parms == null || parms.length != 1)
              {
                  //for standard types we have only one parameter representing the type
                  continue;
              }
              return parms[0].getName();
          }
          log.warning("The SystemEvent source type for " + systemEventClass.getName()
                  + " could not be detected, either register it manually or use a constructor argument "
                  + "for auto detection, defaulting now to java.lang.Object");
          return "java.lang.Object";
      }
docs: A mapper for the handful of system listener defaults
  since every default mapper has the source type embedded
  in the constructor we can rely on introspection for the
  default mapping
  
  @param systemEventClass the system listener class which has to be checked
  @return