Java Naming and Directory Interface

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Java Naming and Directory Interface

• JNDI

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Topics

• Naming and Directory Services
• JNDI Overview
• Features and Code Samples
• JNDI Providers
• References

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Naming Service

• Associate names with objects (bind)
• Retrieve objects by their name (lookup)
• Examples
• RMI Registry
• CORBA Naming Service (COSNaming)
• Domain Name Service (DNS)
• File system

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Contexts

• Contains a set of bindings and lookup operations
• Has its own naming convention
• Examples
• File system directory /
• DNS domain edu
• LDAP cus

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Names

• Logical identifier assigned to an object
• Naming convention defined by Naming System
• Examples
• /dir/dir2/file for UNIX
• drive\dir\string for DOS
• cndan, oISP for LDAP
• www.cise.ufl.edu for DNS

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Names (Cont)

• Atomic Name
• name used in a binding
• Ex. filename in a directory
• Compound Name
• sequence of atomic names
• /usr/bin/ls

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Names (Cont)

• Composite Name
• applies multiple naming systems
• http//www.apl.jhu.edu/weimer/
• URL scheme id http
• DNS www.apl.jhu.edu
• UNIX and webserver /usr/weimer/public_html

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Directory Service

• Can obtain an object with attributes and search
  for objects based on attributes
• Current Directory Systems
• X.500 - ISO standard. Complex.
• LDAP - Simplified X.500 over TCP/IP
• NDS - Novell Directory Services.
• NIS - Directory service for Solaris

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Attributes

• Common LDAP Attributes
• c Country
• o Organization
• ou Organizational Unit
• cn Common Name (typically first or full name)
• sn Users surname

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Naming and Directory Targets

• Resources
• printers
• machines
• Users
• Java Objects !

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Naming Vs. Directory

• Naming Services simply assign logical names to
  addresses or objects
• localhost gt 127.0.0.1
• white pages
• Directory Services add attributes and
  attribute-based searching
• find all hosts that are Sparc Solaris and have
  available disk space
• yellow pages

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JNDI Goals

• Provide a consistent API to access different
  naming and directory services.
• Clients learn one API.
• Different naming and directory systems can be
  combined into one logical system
• New naming service implementations can be added
  with no client modifications

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JNDI Architecture Overview
Java Client Application
JNDI API
JNDI Naming Manager
JNDI Service Provider Interface
DNS
LDAP
CORBA
RMI
Anything
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JNDI Architecture

• Application Programming Interface (API)
• API for client programmer
• Unifying interface
• Service Provider Interface (SPI)
• For vendors enabling JNDI access to their
  naming/directory service

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JNDI API

• Included in Java 2 SDK v 1.3
• Have to download for JDK 1.1 and SDK 1.2
• Packages
• javax.naming
• javax.naming.directory
• javax.naming.event
• javax.naming.ldap
• javax.naming.spi

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Service Providers

• Implementation for underlying products
• Included in Java 2 SDK 1.3
• LDAP
• COSNaming
• JNDI over RMI Registry
• Have to download for previous versions
• http//java.sun.com/products/jndi/

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Common JNDI Tasks

• Obtain reference to initial context
• Context Operations
• List children of a context
• Bind names to objects
• Lookup objects via name
• Create/destroy contexts
• Note NamingException can be thrown from most
  Context operations

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JNDI Contexts
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Obtain Initial Context

• import javax.naming.
• java.util.Properties props new
  java.util.Properties()
• props.put(Context.INITIAL_CONTEXT_FACTORY,
• com.sun.jndi.fscontext.RefFSCont
  extFactory)
• props.put(Context.PROVIDER_URL, file///)
• Context initContext new InitialContext( props )

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Initial Context

• Starting point in the namespace
• All operations performed are relative to the
  initial context
• Specify service provider with property
• props.put(Context.INITIAL_CONTEXT_FACTORY,
• com.sun.jndi.fscontext.RefFSContextFactory )

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Initial Context (Cont)

• Specify provider-specific properties
• LDAP
• props.put(Context.PROVIDER_URL,
  ldap//hostport)
• props.put(Context.SECURITY_PRINCIPAL, user )
• props.put(Context.SECURITY_CREDENTIALS,
  password)
• File System
• props.put(Context.PROVIDER_URL, file//tmp/)
• Create
• InitialContext initContext new InitialContext(
  props )

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List children

• NamingEnumeration children initContext.list()
  
• while( children.hasMore() )
• NameClassPair nc (NameClassPair)
  children.next()
• System.out.println(nc.getName())
• System.out.println(nc.getClassName())
• list() returns a NamingEnumeration of
  NameClassPair objects
• listBindings() returns a NamingEnumeration of
  Binding objects

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Binding Names to an Object

• Bind name to object within a context
• File f new File(/tmp/dan)
• tmpDirContext.bind(dan, f )
• NameAlreadyBoundException occurs if dan is
  already bound in the tmp context
• Can use unbind() or rebind()

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Object Lookup

• Lookup object in a context
• String name Object o initContext.lookup(name)
• name can be compound
• /usr/tmp/dir/myfile
• Filesystem provider returns
• File for files

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Attributes

• DirContext contains an object with attributes for
  each contained binding
• Common LDAP Attributes
• c Country
• o Organization
• ou Organizational Unit
• cn Common Name (typically first or full name)
• sn Users surname

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Basic Search

• Specify a set of attributes that an entry must
  have.
• Specify required attribute values
• Specify attributes to return
• search(String name, Attributes match, String
  retAttrIds )
• Returns NamingEnumeration of SearchResults

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Storing objects

• Object Types to store
• Java Serializable Object
• Referenceable Java Object
• Remote Objects like RMI and CORBA objects

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Federation

• Composite names span multiple namespaces
• ouPeople/tmp/myFile
• File f (File) ctx.lookup(ouPeople/tmp/myFile)
  
• lookup on this name will traverse through LDAP
  and the Filesystem provider to retrieve the file

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JNDI Providers

• LDAP
• com.novell.naming.service.nds.NdsInitialContextFac
  tory
• NIS
• com.sun.jndi.nis.NISCtxFactory
• RMI
• com.sun.jndi.rmi.registry.RegistryContextFactory
• COSNaming ( CORBA Naming System )
• Files
• com.sun.jndi.fscontext.RefFSContextFactory

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Setup Requirement

• For 1.3, essentially nothing. JNDI should be
  included in the distribution along with the 3
  providers
• For Java 2 SDK version 1.2
• jndi.jar in JAVA_HOME/jre/lib/ext
• For jdk 1.1
• Add jndi.jar to the CLASSPATH

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Summary

• Provide a consistent API to access different
  naming and directory services.
• Clients learn one API.
• Different naming and directory systems can be
  combined into one logical system
• New naming service implementations can be added
  with no client modifications

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Resources

• JNDI API Tutorial and Reference, Rosanna Lee and
  Scott Seligman. Addison Wesley, 2000
• Main JNDI Page
• http//java.sun.com/products/jndi/
• Java Lecture Source
• http//www.apl.jhu.edu/jcstaff/ejava/ejava_whatsn
  ew_f00.htm
• Java Online Tutorial
• http//java.sun.com/docs/books/tutorial/