Trading Service (Java Enterprise in a Nutshell)

11.14. Trading Service

This service is analogous to a market-trading context, in which agents make buy offers for items they want (bids) and sell offers for items that they have (asks), and the trading system is responsible for matching the bids and asks to execute trades. In the Trading Service, objects describe the services that they can offer to the system, and clients issue a description of the desired properties of an object. The Trading Service then matches object services with clients seeking these services.

Buyers, or importers, of services use a Lookup interface to advertise their needs, while sellers, or exporters, of services use a Register interface to advertise the properties of their services. If an importer receives multiple hits on a query issued through the Lookup interface, it is given an OfferIterator to iterate through the offers for any that it wants to accept. An Admin interface queries for all outstanding offers and queries and controls parameters related to how the two are matched.