code: public Class<?> attrType(String attr) {
  		Table table = this.table();
  		if (null != table) {
  			return table.getColumnType(attr);
  		}
  		
  		Method[] methods = this._getUsefulClass().getMethods();
  		String methodName;
  		for (Method method : methods) {
  			methodName = method.getName();
  			if (methodName.startsWith("set") && methodName.substring(3).toLowerCase().equals(attr)) {
  				return method.getParameterTypes()[0];
  			}
  		}
  		return null;
  	}
docs: Get attr type
  @param attr
  @return attr type class