Jini


Jini, also called as Apache River, is network architecture for the construction of distributed systems in the form of modular co-operating services.

Jini technology is a service-oriented architecture that defines a programming model which exploits and extends Java technology to enable the construction of secure, distributed systems consisting of federations of well-behaved network services and clients. Jini technology can be used to build adaptive network systems that are scalable, evolvable and flexible as typically required in dynamic computing environments. Jini offers a number of powerful capabilities such as service discovery and mobile code. Jini is similar to Java Remote Method Invocation but more advanced.

The term Jini refers to a set of specifications and an implementation; the latter is referred to as the Jini Starter Kit. Both the specifications and the Starter Kit have been released under the Apache 2.0 license and have been offered to the Apache Software Foundation's Incubator.

Jini provides facilities for dealing with some of the fallacies of distributed computing, problems of system evolution, resilience, security and the dynamic assembly of service components. Code mobility is a core concept of the platform and provides many benefits including non-protocol dependence.

One of the goals of Jini is to shift the emphasis of computing away from the traditional file-system–oriented approach to a more network-oriented approach. Thus resources can often be used across a network as if they were available locally. Jini allows for advanced searching for services through a process of discovery of published services (making Jini akin to the service-oriented architecture concept).

There are three main parts to a Jini scenario. These are the client, the server, and the lookup service.

The service is the resource which is to be made available in the distributed environment. This can include physical devices (such as printers or disk drives) and software services (for example a database query or messaging service). The client is the entity which uses the service. Jini provides a mechanism for locating services on the network that conform to a particular (Java) interface. Once a service is located, the client can download an implementation of that interface, which it then uses to communicate with the service.

The three major components that make up a running Jini system are
1.  The Jini Client—Anything that would like to make use of the Jini service
2. The Service Locator—Anything that acts as a Locator/Trader/Broker between the service and the client, and is used to find services in a distributed Jini system.

The Jini Service
—Any entity that can be used by a client program or another service (for example, a printer, a DVR (this used to say "VCR" - that's how old this software is), or a software entity like an EJB service)

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