Knowledge base: Lightweight Directory Access Protocol (LDAP)

LDAP is protocol mostly used to interchange information about user/login names/emails. Complex definition with links to RFC at wikipedia http://en.wikipedia.org/wiki/LDAP

LDAP provider (directory) is typically database of users/groups. Examples of providers: MS Active Directory, Sun ONE Directory Server, IBM Tivoli server

LDAP client can communicate with LDAP provider and can ask for authentication and according the result returned it could decide what to do. LDAP client can retrieve list of other users/groups.

LDAP client can connect (bind) to LDAP provider using host, port login distinguished name (DN) and password - login DN and password could be empty if LDAP provider allows anonymous bind. Other anonymous operation could be done such a list of users in LDAP etc.

Java program can access to LDAP via JNDI API http://java.sun.com/products/jndi/ or via any other libraries e.g. OpenLDAP http://www.openldap.org/jldap/