Jini Technology

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Jini Technology
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Jini Technology

• Introduction
• Architecture Overview
• Lookup Service
• Programming Model
• Application

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Jini Technology

• Introduction and Architecture Overview

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What is Jini

• A breakthrough initiative based on Java
  technology
• Enables all types of devices to simply connect
  into impromptu networks, making access to and
  delivery of new network services as simple as
  plugging in a telephone.
• Enables all types of digital devices to work
  together in a community put together without
  extensive planning, installation, or human
  intervention.
• Each device provides services that other devices
  in the community may use.

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What is Jini

• A distributed system based on the idea of
  federating groups of users and the resources
  required by those users
• The overall goal is to turn the network into a
  flexible, easily administered tool
• The focus of the system is to make the network a
  more dynamic entity

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Where Jini Technology be Used

• Almost anything that passes digital information
  in and out
• Traditional computer hardware and software
• Consumer appliances such as personal digital
  assistants (PDAs), digital cameras, VCRs, TVs,
  DVD players, cell phones, and CD players.

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An Example Scenario
Three professionals Bob, Sue, and Dave, at
three different sites use JiniTM technology to
pull together a complex project, deploying a host
of different networked devices.
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History of Jini Technology

• The idea of the Jini system sprang from Sun
  cofounder Bill Joy at Sun Aspen Smallworks RD
  lab in 1994.
• Under the leadership of Bill Joy and Jim Waldo
• Ann Wollrath, the inventor and designer for Java
  Remote Method Invocation (Java RMI)
• Ken Arnold, the designer of JavaSpaces
  technology
• Bob Scheifler, a principal of the X Consortium
  and designer of Lookup/Discovery.
• Based on the potential to create a ubiquitous
  network by leveraging the unique distributed
  computing characteristics of Java technology

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History of Jini Technology

• On January 25, 1999, Jini was officially launched
  and the technology is available for download
• By September 1999, 18,000 click-thru agreement
  /downloads of Jini release from Suns web site
• Sun currently has agreement with a wide range of
  technology companies to develop Jini technology
  services, both hardware and software.
• includes Axis, Canon, Datek, Epson, FedEx,
  Mitsubishi, Norwest Mortgage, Novell, ODI,
  Quantum, Seagate, Toshiba, Computer Associates,
  Oki, Salomon Brothers

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History of Jini Technology

• It is expected that by using Jini technology, we
  can enable infinitely connected network of
  services into which anyone will be able to
  plug-and-participate anytime, from anywhere,
  using the simplest possible technology.

As easy to connect to as a telephone dial tone
As persistent and reliable as a radio
As easy to operate as a TV
As powerful as all of the devices connected to it
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Why Jini Technology

• Network plug and work
• Enables a services based architecture
• Spontaneous networking
• Erase the distinction between hardware and
  software
• A distributed computing infrastructure to make
  writing distributed programs easier

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Jini Technology Builds on Java Technology
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Nomenclature

• Key terms used in talking about Jini
• Federation -- A federation consists of a group of
  devices (like printers, hard disks and so on) and
  software programs (any program that is compiled
  down to Java bytecode) that form a single,
  dynamic, distributed system.
• Resource -- The devices and programs within a
  federation are called resources
• Service -- A resource offers a service. A service
  can be storage, communication, computation or
  anything that a resource can do.

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Structure of Jini Technology
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Jini Infrastructure

• Infrastructure is the set of components that
  enables building a federated Jini system
• The lookup service, which serves as a repository
  of services. It reflects the current members of
  the federation and acts as the central
  marketplace for offering and finding services by
  members of the federation
• The discovery/join protocol, a service protocol
  that allows services (both hardware and software)
  to discover, become part of, and advertise
  supplied services to the other members of the
  federation
• A distributed security system, integrated into
  RMI, defines how entities are identified and how
  they get the rights to perform actions on their
  own behalf and on the behalf of others

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Jini Infrastructure - Lookup Service

• The central organizing mechanism for Jini-based
  systems
• The lookup service reflects the current members
  of the federation
• When new services become available on the
  network, they register themselves with a lookup
  service
• When clients wish to locate a service to assist
  with some task, they consult a lookup service

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Jini Infrastructure - Discovery / Join / Lookup
protocol

• Discovery enables clients and services to locate
  lookup services.
• Join enables a service to register itself in a
  lookup service.
• Lookup enables a client to query a lookup service
  for services that can help the client accomplish
  its goals.

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Jini Infrastructure - Registering a Service
1. Service provider broadcasts a discovery packet
onto a well-known port 2. Lookup service monitor
the well-known port for the presence of the
discovery packets 3. Using RMI, the lookup
service replies to the originator of the packet,
finishes the discovery 4. The service provider
joins the lookup service
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Jini Infrastructure - Finding a Service
1. A resource first queries the lookup service
for a particular interface 2. If the interface is
present in the lookup service, the client proxy
of the interface is returned to the resource
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Jini Infrastructure - Using a Service
The resource invokes method of the client proxy
interface.
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Programming Model

• A set of interfaces that enables the construction
  of reliable services, including those that are
  part of the infrastructure and those that join
  into the federation
• Leasing interface defines a way of allocating
  and freeing resources using a renewable,
  duration-based model
• Event and notification interface a notification
  mechanism between services and resources that
  stretches beyond machine boundaries
• Transaction interface wrapping of multiple
  operations on multiple services into a single
  unit of work that either completely succeeds or
  is rolled back

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Programming Model - Leasing interface

• A lease in Jini is a finite duration agreement
  between two Jini entities. A lease is negotiated
  between the entity requesting and the entity
  granting the lease.
• With this design, resources claimed in a lease
  can be automatically released after a period of
  time. A long-running Jini system
• Can effectively recover from disconnection and/or
  partial system failure
• Has the equivalent of a garbage collection
  process for stale and unreferenced entries and
  resources

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Programming Model - Transaction interface

• The transaction interfaces introduce a
  light-weight, object-oriented protocol enabling
  Jini applications to coordinate state changes.
• The transaction protocol provides two steps to
  coordinate the actions of a group of distributed
  objects.
• voting phase each object "votes" whether it has
  completed its portion of the task and is ready to
  commit any changes it made.
• commit phase a coordinator issues a commit
  request to each object.
• Various levels of Atomicity, Consistency,
  Isolation, and Durability (ACID) can be
  implemented and guaranteed

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Programming Model - Event and notification
interface

• Distributed event notification is handled via
  registration to event generating entities and
  providing objects that implement the appropriate
  listener interface
• These interfaces are specially designed to cater
  for the less predictable event propagation
  characteristic over a distributed system.
  Specifically, it caters for having agents or
  middlemen that will manage and handle event
  registration and notification on behalf of client
  objects.

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Services

• Hand-coded using the programming model. Can be
  programmed to do any task suitable of the
  resource
• Services appear programmatically as objects
  written in the Java programming language, perhaps
  made up of other objects.
• A service has an interface which defines the
  operations that can be requested of that service.
  
• The type of the service determines the interfaces
  that make up that service and also define the set
  of methods that can be used to access the
  service.
• A single service may be implemented by using
  other services.

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Separation of interface and implementation

• Service object can be
• completely local proxy
• RMI stub as a proxy
• smart proxy
• Client does not care about network protocol
• Service implementation can evolve over time

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A Jini System in Action - Remote PDA Printing
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References

• http//java.sun.com/features/1999/01/jini_scenario
  .html
• http//www.developer.com/journal/techfocus/080598_
  jini1.html
• http//www.sun/com/jini/whitepapers/architecture.h
  tml
• Professional Java Server Programming, WROX
• http//www.abcomp.be/news/events/receptions/abny99
  /history.html

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Jini Infrastructure - Discovery / Join / Lookup
protocol
Discovery
1. Service provider broadcasts a presence
announcement by dropping a multicast packet onto
a well-known port 2. Lookup services monitor the
well-known port for presence announcement
packets. It opens and inspects the packet when
receives a presence announcement 3. Using RMI,
the lookup service sends an object, called a
service registrar, across the network to the
originator of the packet
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Jini Infrastructure - Discovery / Join / Lookup
protocol
Join
The service provider invokes the register()
method on the service registrar object, passing
as a parameter an object called a service item, a
bundle of objects that describe the service. The
register() method sends a copy of the service
item up to the lookup service, where the service
item is stored.
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Jini Infrastructure - Discovery / Join / Lookup
protocol
Lookup
1. A client invokes the lookup() method on a
service registrar object 2. The client passes as
an argument to lookup() a service template, an
object that serves as search criteria for the
query. The service template can include a
reference to an array of Class objects. These
Class objects indicate to the lookup service the
Java type (or types) of the service object
desired by the client 3. The lookup service
performs the query and sends back zero to many
matching service objects. The client gets a
reference to the matching service objects as the
return value of the lookup() method
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Jini Infrastructure - Service Invocation
Invoke service
Service object can grant clients access to the
service in many ways. The object can actually
represent the entire service, which is downloaded
to the client during lookup and then executed
locally. Alternatively, the service object can
serve merely as a proxy to a remote server. When
the client invokes methods on the service object,
it sends the requests across the network to the
server, which does the real work. The local
service object and a remote server can each do
part of the work as well.
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Jini Technology Benefits

• No configuration hassles or device drivers.
• Devices simply announce themselves and their
  capabilities (service).
• Seamless access to local and remote devices.
• Devices (i.e. printers) can be associated with
  people, places, etc.
• Everyone has access to the same information
  resources.
• For the duration of the meeting everyone has
  access to common resources which means that they
  have a unified and consistent view of their
  immediate network.

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Jini Technology Benefits

• The Resource is there when you need it.
• If another employee needs to show a presentation,
  Mitch can simply relinquish the Projector and let
  the other employee take over transparently.
• It's easy to share information with the team.
• Personal Calendars can be synched up or shared
  "spontaneously" to set up a follow-up meeting for
  example

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Jini Connection Technology Makes Things Work