JNDI

1
Chapter 4 5

• JNDI

2
ltJSP useBean

• In Java Server Pages, you can use a server-side
  java class within a JSP withltHTMLgt.ltJSP
  useBean idmyBean classmypackage.mybean
  /gtlt/HTMLgt
• This name may be misleading. Its not technically
  a bean, that is inherited from the javax.swing
  for instance. It can be a simple java public
  class, that your JSP will instantiate and use via
  its public methods.

3
JNDI

• JNDI (Java Naming Directory Interface) is an
  API that provides a standard protocol for
  accessing any network resource in an
  inter/intranet.
• JNDI allows a Java application to use servers
  that provide network sharing, resource pooling
  and access to their file structures.

4
JNDI - Sun

• JNDI works in concert with other J2EE
  technologies to organize and locate components in
  a distributed computing environment -
  http//java.sun.com/products/jndi/

5
Network Services

• Supported by JNDI are
• Directory ServicesProvides access to directory
  structures or other hierarchical trees of
  objects on a services file system.
• Naming ServicesEnables an application to access
  a remote object by name (through mapping a unique
  ID to each object and its name)

6
Naming Service - Binding

• Mapping between an objects name and its unique
  ID.
• Server creates a unique ID, and user creates a
  recognizable name for this object.
• Examples
• Remote java class can be accessed in an Applet by
  requesting its class name.
• DNS (Domain Naming Service) translates domain
  names to raw IP addresses.

7
Naming Service - Namespace

• Defines the scope of an object.
• Objects must have unique names within their
  namespace, but the same object/name can exist in
  several of these spaces.

8
Naming Service - Namespace

• Objects are identified by its naming convention
  of the namespace. These may consist of Compound
  names, where a (path)/(object) pair is given.
• The other convention is a Composite Name, which
  describe the protocol to use as well as the path
  and resource requested.

9
Service Providers

• These are part of the Name Service, residing on
  the server, that map the JNDI API to the features
  that are supported by this Name Service.
• The API of the Name Service may be proprietary -
  the Service Provider creates a common API (JNDI)
  for these proprietary functions.

10
Service Providers

• LDAP Lightweight Directory Access Protocol
  provides common services for accessing
  files/objects across many (sometimes
  heterogeneous) servers.
• NIS Network Information Service is a unix based
  protocol providing access to those resources
  across servers.
• File Services Provides standard io from Java
  classes to host file systems.

11
Directory Services

• Provides a structured, hierarchical view to
  objects in the name service.
• Through the directory context (nodes on the
  structure), users can query/search the various
  different physical structures as one logical file
  structure.

12
LDAP

• The industry standard directory service for
  enterprise servers, running on TCP/IP.
• Items in the structure can be queried and
  modified based on their context (where they are
  in the structure).
• http//www.ldapcentral.com/

13
JNDI - Goals

• Consistency Uses a common API, with just a small
  amount of classes that leverage an existing java
  class library
• Short learning curve Provides a simple interface
  (may only be two lines of code) to access many
  objects and services.
• API is implementation independent, and open in
  architecture. Providers can add to it if needed.

14
Using JNDI

• Pg 80 - JNDI Architecture Review
• Example in Chapter 5
• Implementation of a File System provider
  (FsContext), where
• directories are context objects
• files are file objects represented by
  java.io.File
• Provides a look into a Naming Service

15
javax.naming

• javax.naming is the package containing the
  Context Interface.
• Context is the starting point (root) of the
  naming/directory service.
• Pg 86 has a sample directory structure to use.
  Context can be set at root (/) or /temp or other
  ...

16
Defining a Context

• Properties p new Properties()
• p.put (Context.INITIAL_CONTEXT_FACTORY,
  com.sun.jndi.fscontext.RefFSContextFactory)
• p.put(Context.PROVIDER_URL,file/tmp/marketing)
  
• InitialContext ctx new InitialContext(p)

17
Searching Objects In A Context

• Elements (File Objects) in a context can be
  LISTED using an Enumeration object
• NamingEnumeration rpts ctx.list(Reports)
• By using the rpts object, each report can be
  retrieved using while ( rpts.hasMore() )
• Each element of rpts is a NameClassPair instance
  (the name and the class to cast it to).

18
Searching Objects

• To LOOKUP (retrieve) an object
• File rpt (File) cts.lookup(\reports\Report1.txt
  )
• rpt can now be used as a java.io.File object.

19
LIST Example

• Hashtable env new Hashtable()
• env.put(Context.INITIAL_CONTEXT_FACTORY,"com.sun.j
  ndi.fscontext.RefFSContextFactory")
• // Specify the filesystem to search in this
  example
• env.put(Context.PROVIDER_URL,"file/tmp/marketing"
  )
• Context initCtx new InitialContext(env)
• NamingEnumeration nl initCtx.list("reports")
• while (nl.hasMore())
• item nl.next()
• System.out.println("item's class is
  "item.getClass().getName() )
• System.out.println(item)

20
LOOKUP Example
Hashtable env new Hashtable() env.put(Contex
t.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.fsco
ntext.RefFSContextFactory") env.put(Context.PROV
IDER_URL,"file/tmp/marketing") Context initCtx
new InitialContext(env) File f
(File)initCtx.lookup("reports/report1.txt")
21
Binding Objects

• Binding brings together
• object name
• object class
• object instance
• Used for operations such as adding, deleting,
  renaming or moving objects.

22
Examples

• Deleting
• ctx.unbind(reports/Report1.txt)
• Renaming
• ctx.name(reports/Report1.txt,
  reports/Report9.txt)
• Add another Context
• ctx.createSubcontext(ArchiveReports)

23
References To Java Objects

• JNDI provides another alternative to serializing
  java objects.
• References can be defined, which contain the
  instructions for how to create an object that
  isnt necessarily serializable.
• Instead of the object being bound to a
  naming/directory service, the address is stored
  in an ObjectFactory.

24
Object Factory

• An Object Factory holds references that JNDI uses
  to retrieve objects that arent bound directly to
  a service.
• Between the Object Factory and the objects, are a
  Reference object that holds
• class name of referenced object
• RefAddr, which is the actual address

25
Example
env.put(Context.PROVIDER_URL,
"file/tmp/marketing/presentations/") Context
initCtx new InitialContext(env)
initCtx.rebind("Susan", new Car("Toyota","Camry"))
initCtx.rebind("Cheryl",new Car("Saturn","Coupe
")) initCtx.rebind("Nicole", new
Car("Ford","Bronco")) Car c
(Car)initCtx.lookup("Cheryl")
26
Example
public class Car implements Referenceable
public Reference getReference() throws
NamingException String cName
Car.class.getName() StringRefAddr cRef
new StringRefAddr("Car Des",
make "" model) String cfName
CarFactory.class.getName() Reference
ref new Reference(cName, cRef, cfName, null)
return ref
27
Example
public class CarFactory implements ObjectFactory
public Object getObjectInstance(Object obj,
Name name, Context ctx, Hashtable env) throws
Exception if (obj instanceof
Reference) Reference ref
(Reference)obj if
(ref.getClassName().equals(Car.class.getName()))
RefAddr addr ref.get("Car
Des") if (addr ! null)
String s (String)addr.getContent(
) int n s.indexOf("")
String make
s.substring(0,n) String
model s.substring(n1)
return new Car(make,model)
return null
28
javax.naming.directory

• Directory package provides an additional api for
  directory specific services in addition to the
  naming services.
• Provides
• Directory searching using object attributes
• Search optimization
• Modification of an objects attributes

29
Searching Objects

• env.put(Context.INITIAL_CONTEXT_FACTORY,
  com.sun.jndi.ldap.LdapCtxFactory)
• env.put(Context.PROVIDER_URL, ldap//localhost/o
  JNDIExample)
• DirContext dctx new InitialDirContext(env)
• Attribute Searching
• Attributes attrs new BasicAttributes(true)
• attrs.put(new BasicAttributes(email) )
• attrs.put(new BasicAttributes(website,www.cnn.c
  om) )
• NamingEnumeration result dctx.search(ouPeople
  , attrs)

30
Advanced Searching

• SearchControls sc new SearchControls()
• Filters
• String filter ( (cnS) (account gt 1000) )
• NamingEnumeration result dctx.search(ouPeople
  , filter)
• Limiting Scope
• String attrIDs cn, email
• sc.setReturningAttributes(attrIDs)
• sc.setSearchScope(SearchControls.OBJECT_SCOPE)
• NamingEnumeration result dctx.search(ouPeople
  , filter, sc)

31
Advanced Searching

• Control Number Of Results
• sc.setCountLimit(5)
• Time Limit
• sc.setTimeLimit(2000)