code: protected String getMessageCode(Object o) {
  		if (o instanceof TypeResolvable) {
  			String type = ((TypeResolvable) o).getType();
  			if (type != null) {
  				return type;
  			}
  		}
  		return ClassUtils.getShortNameAsProperty(o.getClass());
  	}
docs: Determines the messageCode (key in messageSource) to look up.
  If <code>TypeResolvable</code> is implemented, user can give a custom code,
  otherwise the short className is used.
  
  @param o
  @return