Jini Technology

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Jini is the name for a distributed computing environment, that can offer ``network plug and play''. A device or a software service can be connected to a network and announce its presence. Clients that wish to use such a service can then locate it and call it to perform tasks. This can be used for mobile computing tasks where a service is only connected to a network for a short time, but more generally can be used in any network where there is some degree of change.


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JINI TECHNOLOGY : JINI TECHNOLOGY Neenu Prasad

Contents : Contents Introduction What is Jini? Where Jini technology be used? Why Jini technology? Components of Jini Jini Infrastructure Programming model Benefits Conclusion

Introduction : Introduction Jini technology is a service oriented architecture that defines a programming model which both exploits and extends java technology to enable the construction of secure distributed systems. Jini is an extension of java Java consists of one virtual machine Jini is a kind of virtual network

What is Jini ??? : A distributed system based on the idea of federating groups of users and the resources required by those users. It has the special ability to "recognize" devices that have just been plugged into the network without prior knowledge of the device. What is Jini ???

Where Jini Technology be Used : Traditional computer hardware and software. Consumer appliances such as personal digital assistants (PDAs), digital cameras, VCRs, TVs, DVD players, cell phones, and CD players. Where Jini Technology be Used

Why Jini Technology : Network plug and play. Spontaneous networking. Erase the distinction between hardware and software. A distributed computing infrastructure to make writing distributed programs easier. Why Jini Technology

JINI INFRASTRUCTURE : JINI INFRASTRUCTURE

Jini Components : … and yes, and the network connecting all three - generally be running TCP/IP a service , such as a printer, scanner, storage device, a software service etc. a client which would like to make use of this service. a lookup service (LUS) - a service locator Jini Components

JINI PROCESS : JINI PROCESS Discover: find a Lookup service. Join: send a copy of the service proxy to the Lookup service. Lookup: request a service. Receive a copy of the service proxy. Access service.

PowerPoint Presentation : Discovery : Service provider broadcasts a presence announcement . Lookup services monitor the well-known port for presence announcement packets. Using RMI, reply is given ie a service registrar() object is given back. Jini Service LUS – Lookup Service 1. Jini service discovers LUS

Discovery protocols : Discovery protocols The process of finding the available lookup services. Discovery protocols Unicast discovery Multicast discovery

PowerPoint Presentation : Service Registrar Jini Service Allows services to register as Jini services with the LUS register (ServiceItem, lease)

PowerPoint Presentation : register() contains two arguments a ServiceItem() and lease duration . Service Item Class : ID for the service (automatically generated by LUS) Attributes for service - list of objects

PowerPoint Presentation : When a service has registered - its available for use by clients Clients use lookup to find services Service Registrar ServiceTemplate: contains the search query typically search using Java type (i.e. interface) Lookup(ServiceTemplate t) Jini Client (Consumer) (Obtain ServiceRegistrar using Discovery)

Using a service : Using a service Jini client uses proxy to contact Jini service directly Jini Service Jini Client (Consumer)

PROGRAMMING MODEL : PROGRAMMING MODEL

Programming Model : Contains a set of interfaces . Leasing interface. Event and notification interface. Transaction interface. Programming Model

PowerPoint Presentation : A lease in Jini is a finite duration agreement between two jini entities. With this design, resources claimed in a lease can be automatically released after a period of time. Lease are either exclusive or non-exclusive Used to keep track of active Jini services

LEASING IN JINI : LEASING IN JINI Can be set by service or controlled by LUS Services use leasing to register that they are alive, but allow themselves to be ``timed out'' if they have failed or if they are unreachable. Setting Lease Duration: Grant Lease 4 Second Lease Scenario 1 2 3 4 1 2 3 4 1 2 3 4 LUS Jini Service

Programming Model - Transaction interface : Transaction: a grouping of operations such that they all occur atomically; The operations either … All succeed (commit) Or All fail (abort) Two- Phase Commit: a protocol for coordinating transactions across multiple nodes Programming Model - Transaction interface

Two-Phase Commit Protocol : 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 . Two-Phase Commit Protocol

TRANSACTION PROPERTIES : TRANSACTION PROPERTIES Atomicity: All the operations occur or none of them do Consistency: Must leave the system in a consistent state Isolation: Ongoing transactions should not affect each other Durability: The results should be persistent as the entity on which the transaction commits

Programming Model – Event and notification interface : Jini Architecture supports distributed events. An object may also allow other objects to register interest in events in the object and receive a notification of the occurrence of such event .This enables distributed event-based programs to be written with a variety of reliability and scalability guarantees. Programming Model – Event and notification interface

JAVA RMI : JAVA RMI The communication between the services happens using Remote Method Invocation (RMI) supplied from java. RMI not only allows transfer of data from an object to other through net ,but also allows entire object to move. Great part of simplicity of jini system is concurred from the ability to move the code, encapsulated into object through the net.

Jini Scenario: Example : Jini Scenario: Example 3. invokes register() on ServiceRegistrar object to register service 2. receives a ServiceRegistrar object Jini Service Jini Client (Consumer) LUS – Jini Lookup Service 1. Jini service discovers LUS 7. Jini client uses Java proxy to communicate and use the Jini service 5. receives a ServiceRegistrar object 4. Jini service discovers LUS 6. invokes lookup() on ServiceRegistrar to locate desired service (returns Java proxy)

Jini Technology Benefits : Devices simply announce themselves and their capabilities (service). Devices (i.e. printers) can be associated with people, places, etc. Everyone has access to the same information & resources. It's easy to share information with the team. Os and hardware independent Jini Technology Benefits

Conclusion : Jini provides an extensive framework for developing flexible and robust distributed systems. In addition to that it offers capabilities ,which are required to fulfill the needs of modern end users of the network services. Conclusion

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.html Professional Java Server Programming, WROX http://www.abcomp.be/news/events/receptions/abny99/history.html References

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Neenu Prasad
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