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Separating UI and Functionality
The Flexible Way to Architect a Jini Service
by Bill Venners
October 1999

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Universal Access

Separating UI and functionality is a flexible way to architect Jini services, because the same service object can be used with more than one UI object. This enables the same service to be accessed from many different kinds of Jini-enabled computers and devices. Different devices have different user interface capabilities. For a given service, a service provider can create multiple UI objects, each of which is geared for a different set of capabilities, and associate them with the service. Third party developers can potentially create their own UI objects to supplement those provided by the service provider. Thus, a Jini service architecture in which functionality is separated from UI enables users to access a service via many different kinds of Jini-enabled devices.

A separation of UI and functionality also makes it possible to make a Jini service accessible to devices that are not Jini enabled. A device that can't host a Jini service object and UI object itself can ask a "service host" to host the service and to place a "protocol adapter" object between it and the service. As shown in Figure 3, a a non-Jini device talks to a protocol adapter via a network protocol. The protocol adapter talks to the service object. Similar to the way a user adapter adapts a service to a human user, a protocol adapter adapts a service to clients, including non-Java and non-Jini clients, that understand a particular protocol.

Figure 3. A Protocol Interface object "adapts" a service to a non-Jini client.

Jini service hosts could be deployed in a local area environments. Non-Jini clients could discover a nearby service host and ask it to host a service and protocol adapter. If no nearby service host exists, the non-Jini client could contact a distant service host with which it maintains a long-term relationship. Through service hosts and the appropriate set of protocol adapter objects, service providers oculd extend the reach of their Jini services to the non-Jini world.

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