I have a very simple web app on a linux box that I need to secure when they log into the application itself using Active Directory. Right now I have figured out how to authenticate a user's username and password using this tutorial http://www.javaxt.com/Tutorials/Windows/How_to_Authenticate_Users_with_Active_Directory
But I still can't seem to figure out how to check if they are in a specific group. This is my first enterprise development project, so I've never had to wrangle with AD or LDAP before. Any suggestions on how to build upon the tutorial to incorporate a check for a group?