Retun messages from Action

Hi,

I have a action in explorer which run some controls on a directory content. It's a java action extending ActionExecuterAbstractBase.
The action is available via the share interface for the users.

I want some return my action more precise that sucess/failure. I would like message displayed to the user to let them know what are the result like :

- Folder validated.
- File XX.csv is missing.
- File XX.xml is malformed
- ....

How can return message from my action ?

Thank you