There are so many ways you can integrate LDAP with Liferay that I think a whole book could be filled with examples. Clearly this is a consequence of the many different scenarios you might face in your company.
The showcase I am presenting is:
1. ApacheDS hosts users and groups (roles and groups are the same on the LDAP side in other words we do not have the diferentiation Liferay does have)
2. ApacheDS is accessible from spring security
3. ApacheDS is accessible from Liferay 5.2.3 LDAP implementation following the below user stories.
I have documented already the ApacheDS setup. Of you have not setup ApacheDS read here.
I have also documented on the same link how to get Spring security working with ApacheDS.
Liferay LDAP authentication user stories:
1. When a user is set in LDAP, Then the user can login with his credentials when accessing Liferay even if the user has never been set in Liferay
2. When a user is assigned to a group/role in LDAP, Then after user login the new group and the user-group association will be created in Liferay
3. When a user is detached from a group/role in LDAP, Then after user login the user-group association will be removed.
The above guarrantees that we can handle the setup of users for both applications (Portlets and Servlets applications) in just one LDAP server.
I thought this was going to be an easy plumbing but it turned to be not that easy. I posted the issue and continued investigating to arrive to the following solution.
1. Spring Security will work only if group contains users (uniqueMember attribute in the group cn)
2. Liferay can work as expected only if user contains groups (any attribute that points to a valid group cn)
3. I have added then an extra attribute to users (ou) which basically closes a cyclic reference between users and groups.
4. See below for the configuration in liferay. Note that I do not include the groups section as in Liferay you must decide either to import users or groups. If you import groups you will not be able to login in version 5.2.3 as I posted in the issues link. I do not show the import/export section as I do not import nor export users and roles. As said before this showcase is precisely about leaving those tasks to LDAP alone. Performance wise this is a good decision BTW.
5. Of course we need to build an application that handles this cyclical reference.