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Java Naming and DirectoryInterface (JNDI)

Vijay Bhatt

NCST Juhu, Mumbai

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Agenda• What is JNDI?

• Naming and Directory Services

• Naming Concepts

• Issues

• JNDI Architecture

• Programming with JNDI

• Role of JNDI in J2EE

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• Class.forName("com.microsoft.jdbc.

sqlserver.SQLServerDriver");

• cnn = DriverManager.getConnection

("jdbc:microsoft:sqlserver://siddh

ant:1433",“username",“password");

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• Context ctx = new InitialContext();

• DataSource ds =

(DataSource)ctx.lookup(“myname”);

• Connection con = ds.getConnection(“abc”,”***”);

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JNDI

Java Naming and Directory Interface (JNDI) provides a standard interface for Java applications to access naming and directory services.

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Naming Service

• Naming Service performs:

– Binding: Associating names with objects

– Lookup: Find an object based on a name.

• Examples: DNS and File systems

• Examples:

– DNS

– Filesystems

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Directory Service

• Directory is a naming service that stores

objects with attributes.

– Usernames and passwords etc stored in attrs.

• Tree like structure

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Names• Atomic name is a indivisible component of a

name

– in /etc/fstab, etc and fstab are atomic names.• Compound name is zero or more atomic

names put together.

– /etc/fstab is a compound name

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Binding• Binding is an association of a name with an object.

– Filename “autoexec.bat” has a binding to some file data on the disk.

– “c:\windows” foldername is bound to a folder on your drive.

• Compound name such as /usr/people/ed/.cshrc

consists of multiple bindings, one to usr, one to

people, one to ed, and one to .cshrc.

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Context• Contains zero or more bindings.

– Each binding has a distinct atomic name.• /etc contains files named mtab and exports.• The /etc folder is a context containing bindings

with atomic names mtab and exports.• mtab and exports are each bound to a file on

the disk.

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Sub-Context

• /usr – CONTEXT – /usr/people – SUB-CONTEXT – /usr/bin – SUB-CONTEXT – /usr/local – SUB-CONTEXT• Each atomic name is bound to a sub-context the

subfolder.• Subcontext are full-fledged contexts• Can contain more name-object bindings, such as

other files or other folders.

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Naming System and Namespaces

• Naming system: A connected set of

contexts.

• Namespace: all the names contained within

that naming system.

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InitialContext

• Starting point for exploring a namespace.

• Starting point for performing all naming and

directory operations.

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Issues• Many naming and directory products. – Netscape Directory Server – MicrosoftActiveDirectory• Various naming and directory protocols: Each directory standard has a different protocol for accessing the directory. – Lightweight Directory Access Protocol (LDAP) – Network Information System (NIS) – Novell’s Network Directory System (NDS)• EveryDS has it’s ownAPI.

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Introducing JNDI• Standard interface to interact with naming and

directory systems.• For Java programs.• Provides common interface to disparate

directories: Same API for LDAP and NIS NDS.• Used in EJB, RMI-IIOP, JDBC for operations like

locating entities i.e. Users, Machines (e.g. printer),

Objects, Services (e.g. datasource) etc.

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JNDI Architecture

• The client API

– Allow Java code to perform directory

operations.• The Service Provider: Driver• The Service Provider Interface (SPI)

– An interface to which naming and directory

service vendors can plug in.

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JNDI Packages

The JNDI comprises of 5 packages• javax.naming – Contains classes and interfaces

for accessing naming services• javax.naming.directory – Extends javax.naming

and provides functionality to access directory services in addition to naming services

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JNDI Packages• javax.naming.event – Classes and interfaces for

supporting event notification in naming and directory services

• javax.naming.ldap – Classes and interfaces for using features that are specific to LDAP v3 that are not already covered by the more generic javax.naming.directory

• javax.naming.spi – Vendors develop their naming/directory services conforming to SPI. Applications can then access these services through the JNDI API

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InitialContextFactory• Used to acquire an initial context• Implementation of the JNDI driver: Knows the specific semantics of a particular directory structure.• bootstrapping.• Necessary information for JNDI to acquire that initial context. – The IP address of the J2EE server – The port number that the J2EE server accepts – Any username/password necessary to use the

J2EE server.

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javax.naming.Context ctx = new javax.naming.InitialContext (System.getProperties()); java -Djava.naming.factory.initial= com.sun.jndi.fscontext.RefFSContextFactory -Djava.naming.provider.url= file:c:\examples.InitCtxclass of the JNDI driver• provider URL: URL that the service provider accepts for bootstrapping.

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Other JNDI operations Methods invoked on a Context• list() - list of contents available at the context.

– names of objects bound to the JNDI tree

– subcontexts.• lookup() - look up objects bound to the JNDI tree

– Return type is driver specific

• RMI-IIOP java.rmi.Remote

• file system java.io.File

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• rename() - give a new name to a context – c:\temp to c:\tmp• createSubcontext() - create a subcontext at the context – c:\foo\bar at the folder c:\foo.• destroySubcontext() - destroy a subcontext of the context – Destroy c:\foo\bar from the folder c:\foo.• bind() – associates a name to a content and stores it at the Context – JNDI drivers accept different parameters to bind()• rebind() - forces a bind even if some object is already bound to the name.

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Bindingimport javax.naming.*; public class Startup { public static void main(String args[]) throws

Exception { AccountImpl acct_impl = new AccountImpl(); Context ctx = new InitialContext

(System.getProperties()); ctx.rebind(“myname", acct_impl); } }

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Looking Upimport javax.naming.*; import java.rmi.*; public class Client { public static void main (String[] args) throws

Exception { Context ctx = new InitialContext (System.getProperties());

Object remoteObject = ctx.lookup(“myname"); Account account = (Account) javax.rmi.PortableRemoteObject.narrow ( remoteObject, Account.class); int b = account.method1(5));}}

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Role of JNDI in J2EE

• J2EE servers have a JNDI implementation.• Used to Look up beans.• Connect to resource factories

– JDBC DataSource

– Java Message Service (JMS) drivers• Acquiring a reference to the Java

Transaction API’s (JTA) UserTransaction

interface.

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References

• Mastering Enterprise JavaBeans by Ed

Roman et. al. (Wiley)

• JNDI Tutorial on java.sun.com

• Java Server Programming J2EE Edition –

Volume 1 – Wrox.

• Java Enterprise in a nutshell – David

Flanagan et. Al. – O’reilly