| Jini Technology Infrastructure: Lookup Service
| The Jini Lookup Service is essentially a bulletin board repository for all services available on the network. It constantly searches for Discovery packets and allows those services to register (of Join), enabling the service and its interface to become a part of the overall Jini community. Characteristics uploaded into Lookup Service include all value-added services provided by the device or application, such as drivers, help wizards, attributes, and so on. The Lookup Service then stores discovered services as an extensible set of Java application objects, including all of the information/attributes of those services.
| For example, when a printer registers with the Lookup Service, it loads a printer driver or an interface to the driver into the Lookup. Then when someone wants to use that printer, he or she downloads the driver and driver interface from the Lookup onto their client device. The printer might also load other value-added services into the Lookup Service. For example, the printer might offer color printing, or support for PostScript. It might also have help wizards that will run on the client device.
| Its important to note that service objects are only downloaded as required. Objects in a lookup service may include other lookup services -- thus providing hierarchical lookup. Further, a lookup service may contain objects that encapsulate other naming or directory services, providing a way for bridges to be built between a Jini technology’s Lookup Service and other forms of lookup service.Of course, references to the Lookup Service may be placed in these other naming and directory services, providing a means for clients of those services to gain access to a Jini technology federation.
| Lastly, a service is added to the Lookup Service by a pair of protocols called Discovery and Join — first the service locates an appropriate lookup service (by using the Discovery protocol), and then it joins it (by using the Join protocol). The basic Lookup Service interface provides all that is needed — registration, access, search, and removal functions.