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Directory service basics

Directory service

A directory is a connected set of directory objects. A directory service is a service that provides operations for creating, adding, removing, and modifying the attributes associated with objects in a directory. The service is accessed through the JNDI interface.


Directory Concepts

Many naming services are extended with a directory service. A directory service associates names with objects and also allows such objects to have attributes.

A directory object (directory entry) represents an object in a computing environment.

Attributes

An attribute has an attribute identifier and a set of attribute values. An attribute identifier is a token that identifies an attribute independent of its values.


Reverse lookup aka Searches

Reverse Lookups in a directory service is known as a search. You can look up a directory object by supplying its name to the directory service.
When you search, you can supply not a name but a query consisting of a logical expression in which you specify the attributes that the object or objects must have.
The query is called a search filter. This style of searching is sometimes called reverse lookup or content-based searching.

What about lookups?

Since DirContext is derived from Context, it has all the operations corresponding to Context. You could lookup objects or subcontexts from a context.

Examples of Directory service providers:

NT Domains: was developed by Microsoft to provide directory services for Windows machines prior to the release the LDAP-based Active Directory in Windows 2000.
Domain Name System: (DNS), the first directory service on the Internet, which is still used everywhere today.
Network Information Service: (NIS), was Sun Microsystems' implementation of a directory service for Unix network environments.
LDAP: (Lightweight Directory Access Protocol), most commonly used protocol for any directory like services.

Directory Context

Just like the Context object in a naming service we have a DirContext for directory services.

DirContext also behaves as a naming context by extending the Context interface. This means that any directory object can also provide a naming context. For example, a directory object for a person might contain attributes about that person as well as provide a context for naming objects, such as the person's printers and file system relative to that person directory object.


Discussions that follow will use LDAP as an example. Continue reading: Introduction to LDAP

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