I would like to use JBoss for the authentication & autorization of a user from LDAP directory (Active Directory).
Q : how use Jboss security with a LDAP to guarantee a better safety : I must used jaas api or another api (please give me un example)
Did you try reading the wiki page regarding this? Its a great place to start:
Using this module will allow you to log in (authentication) and set up roles (authorization).