Question
What is Jini™ technology?
Answer
Jini technology is an architecture for the construction of systems from objects and networks. Jini technology provides a simple infrastructure for delivering services in a network and for creating spontaneous interaction between programs that use these services regardless of their hardware/software implementations. Any kind of network made up of services (applications, databases, servers, devices, information systems, mobile appliances, storage, printers, etc.) and clients (requesters of services) can be easily assembled, disassembled, and maintained on the network using Jini technology. Services can be added or removed from the network, and new clients can find existing services - all without administration.

Question
Who are the architects of Jini technology?
Answer
Under the leadership of Bill Joy and Jim Waldo, some of the best minds in distributed computing worked on the Jini technology project. The team included Ann Wollrath, the inventor and designer for Java[tm] Remote Method Invocation (Java RMI), Ken Arnold, the designer of JavaSpaces[tm] technology and co-author of the book, "Java programming language" with James Gosling, and Bob Scheifler, a principal of the X Consortium and designer of Jini lookup and discovery.

Question
What are the benefits of Jini technology?
Answer
Jini technology is all about simplifying interactions on a network. The Java platform started it, now Jini technology furthers it. Simplification means improved productivity, cost savings, and ease-of-use. It will allow ISVs, IHVs, and component manufacturers the ability to expand into new markets, offering network-based delivery of innovative products and services. Software written to the Jini specification also allows traditional service providers the ability to dynamically add and manage network services.

The Jini architecture is also designed to handle the network outages and changes of configurations that happen in real networks over time.

Question
How does Jini technology work?
Answer
The Jini architecture lets programs use services in a network without knowing anything about the wire protocol that the service uses. One implementation of a service might be XML-based, and another RMI-based, and a third CORBA-based. The client is, in effect, taught by each service how to talk to it. A service is defined by its programming API, declared as a Java programming language interface.

When a service is plugged into a network of Jini technology-enabled services and/or devices, it advertises itself by publishing a Java programming language object that implements the service API. This object's implementation can work in any way the service chooses. The client finds services by looking for an object that supports the API. When it gets the service's published object, it will download any code it needs in order to talk to the service, thereby learning how to talk to the particular service implementation via the API. The programmer who implements the service chooses how to translate an API request into bits on the wire using UPnP, RMI, CORBA, or a private protocol.

In other words, the Jini architecture uses objects that move around the network to make each service, as well as the entire network of services, adaptable to new strategies over time.

Question
Will Jini technology support legacy systems?
Answer
The Jini architecture lets you integrate legacy systems without modification. The basic approach requires only that somewhere in the network there is a Java virtual machine that will execute the required Jini technology on the legacy system's behalf. This is one of the powerful features of the Jini architecture -- a legacy system enabled in this fashion is a full-fledged service in a Jini technology system, not a second-class citizen. If you prefer, you can instead add some small amount of code to the legacy system to make it directly Jini technology-enabled, but this is not necessary.

Jini technology can run on any communication protocol, on any device, for any service, ensuring compatibility and reliability for hardware and software that has been build according to the Jini specifications.

Question
Is Jini technology available now? How do I get it?
Answer
Yes. The source code and the specifications for Jini technology releases are available on the web at http://www.sun.com/jini/. You will be required to accept the terms of the Sun Community Source License (SCSL) in a click-through process.

Question
How is Jini technology being used today?
Answer
Companies are using Jini technology to build communities of services out of simple pieces of hardware and software that have been built according to the Jini specification. Examples range from business enterprises, home networking, and battlefield implementations, to a Jini technology-enabled car.

Question
What other technologies compete with the Jini architecture?
Answer
None. The Jini architecture is the only technology in the marketplace that moves objects around the network to hide wire protocols as implementation details. The API that defines a service is simply a list of what the service does. How it does it is up to the implementation. Existing technologies rely on agreeing, not only on what remote objects will do, but also how requests are transmitted on the wire. Only the Jini architecture makes the details of "how" a service uses the network into an implementation detail that can differ between implementations of the same service without changing the client code.

Question
How does Jini technology fit with complementary network technologies?
Answer
There are many complementary technologies that can take advantage of the capabilities of the Jini architecture. Because the Jini technology hides the details of how a service API is implemented, the Jini architecture can be used with a variety of network technologies to integrate them into a single network of services that clients use without any modification.

The following paragraphs are examples of a few of them:

• Universal Plug and Play (UPnP) is a protocol for data transmission focused on developing XML standards for home networking, operating primarily at the connectivity level of a network stack focusing on devices. Once devices connect to a network, there is a need for an advanced service delivery architecture that can deliver services and a higher order of interoperability to networked devices. This is where Jini technology and UPnP can work together.
  
  In a Jini technology-enabled network of services and/or devices, a UPnP device would be published as a service that implements the relevant API by translating method requests into appropriate XML on the wire, and translating any returned results into the terms of the API.
  
  UPnP works in static systems where every client can be told, in advance, how to talk to every service implementation. Because the Jini architecture relies upon telling the client how to talk to a new service via downloaded code, a network of Jini technology-enabled services and/or devices is able to accommodate changes over time with greater flexibility.
  
  Any connectivity scheme, including UPnP, can interoperate with Jini because Jini technology is wire-protocol and transport-protocol neutral. The Jini architecture also allows UPnP devices to work in the same network as devices using other protocols.

• SLP (Service Location Protocol) is a mechanism for dynamically finding services on the network based on a particular wire protocol. SLP defines services in terms of string names. As with UPnP, SLP does not use mobile code, and so clients must know, in advance, how to talk to any service they will ever use. A bridge could publish SLP services into a Jini technology-enabled network.

• Bluetooth is a technology specification for establishing wireless network connections using low-cost, short-range radio links between PDAs, laptops, mobile phones, and other wireless portable devices. Because it establishes network connections, it can be used as a transport mechanism in a network of Jini technology-enabled services and/or devices transparent to clients who connect to services via Bluetooth.

• Firewire is focused on making it easy to build a high-speed local network of consumer devices and computer peripherals in a home. Because Firewire is a networking technology, like Bluetooth, it is another way that a network of Jini technology-enabled services and/or devices can be transparently connected to a larger network.

JINI - FAQ