Jini Technology
Abstract
Part of the original vision for Java, it was put on the back burner while Sun waited for Java to gain widespread acceptance. As the Jini project revved up and more than 30technology partners signed on, it became impossible to keep it under wraps. So Sun cofounder Bill Joy, who helped dream up Jini, leaked the news to the media earlier this month. It was promptly smothered in accolades and hyperbolic prose. When you plug a new Jini-enabled device into a network, it broadcasts a message to any lookup service on the network saying, in effect, "Here I am. Is anyone else out there?" The lookup service registers the new machine, keeps a record of its attributes and sends a message back to the Jini device, letting it know where to reach the lookup service if it needs help. So when it comes time to print, for example, the device calls the lookup service, finds what it needs and sends the job to the appropriate machine.
Description of Jini Technology
Jini actually consists of a very small piece of Java code that runs on your computer or device. Jini lets you dynamically move code, and not just data, from one machine to another. That means you can send a Java program to any other Jini machine and run it there, harnessing the power of any machine on your network to complete a task or run a program So far, Jini seems to offer little more than basic network services. Don't expect it to turn your household devices into supercomputers; it will take some ingenious engineering before your stereo will start dating your laptop.
Jini can run on small handheld devices with little or no processing power, but these devices need to be network-enabled and need to be controlled by another Jini-enabled hardware or software piece by proxy. The first customer shipment is slated for the fall. Jini-enabled software could ship by the end of the year, and the first Jini-enabled devices could be in stores by next year. Security. Jini will use the same security andauthentication measures as Java. Unfortunately, Java's security model hasnot been introduced yet.
Where Jini Technology be Used
Almost in every devices that passes digital information in and out like
1. Traditional computer hardware and software
2. Consumer appliances such as personal digital assistants (PDAs), digital cameras, TVs, DVD players, cell phones, and CD players.
Jini 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.
Discovery
A client that wants to use a particular service finds the appropriate server by looking in the Jini lookup service. But before that the client has to locate the Jini lookup service. This can be done by a process called discovery. Jini specification for this defines at the network level the protocol by which clients can find the lookup service. There are two ways in which a client can discover the Jini lookup service:
Multicast discovery - the client sends out a multicast request of a specified format. All Jini lookup services that come across the request will respond to it, and the client is said to have discovered the lookup services.
Unicast discovery - In this, the client should attempt to connect to a lookup server having known the existence and location of the lookup server. This is in a sense not discovery. The discovery protocol uses a combination of both unicast and multicast discovery in order to find lookup servers.
