Directory Service Concepts

The primary functionality of the naming service is to map logical names to objects. A directory service extends these capabilities of the naming service by storing meaningful attributes along with the objects. These attributes can be used to search in the directory service for stored objects. A directory service is essentially a simple database that provides the ability to query and search based on filters.

Figure 9.5 shows a typical directory service with server objects registering themselves with the directory service using name identifiers and attributes and client applications obtaining the server object reference by querying the directory service with the name identifier and attributes used by the server objects. The interactions between the server objects and the directory service and between the client applications and the directory service happen entirely by using the JNDI API.

Figure 9.5. Block diagram of clients and servers using a directory service.

Different directory services are available. The most widely used directory service is the Lightweight Directory Access Protocol (LDAP). LDAP provides both naming and direc tory services. LDAP is normally used in enterprises as a common database to store user information such as user ID, password, department details, and so on. This LDAP database is leveraged as a directory service to authenticate users who are using different enterprise applications. Enterprise Java applications access the information in the LDAP database using the JNDI API.

You have gained an understanding of naming and directory services. Now take a look at the JNDI architecture and the different classes and interfaces in the JNDI API. You will also see how the classes and interfaces in JNDI can be used to write applications to access directory and naming services.