The book starts with what Jini is and how it works. (In short, Jini allows Java clients to invoke remote services easily through Java.) The authors present a chat message server and explain the Jini architecture where clients look up and "lease" remote services.
The heart of this book is its coverage of classes in the Jini specification. First there's an overview of Jini illustrated with a printer service. Then it's a close look at how clients "discover" Jini services, either through multicast or unicast protocols. (The authors also present useful built-in utility classes here.)
Next comes material on storing entries for Jini services (used for identifying them across the network) and the classes used to "lease" remote services. An interesting section on remote events contrasts them with local JavaBean events. Then it's on to Jini transactions, including the two-phase commit process used to manage work done remotely.
Later the book turns to the new JavaSpaces classes, which permit sharing data between Java processes in order to facilitate parallelism. An intriguing appendix reprints a white paper in which the Sun team outlines its philosophy of distributed computing. (They argue that local and remote objects need to be handled differently: object location transparency is a myth.)
With a mix of technology briefing and nuts-and-bolts detail, The Jini Specification delivers a valuable perspective on the latest advance in Java distributed computing from Sun. --Richard Dragan
]]>After a foreword by distributed computing pioneer David Gelernter, the book provides a short technology overview describing the makeup of JavaSpaces. The authors atomize their description of JavaSpaces as an overseer application that lets programs running on separate computers store and share persistent data. While the JavaSpaces API is by itself remarkably simple, this book demonstrates with deliberate fanfare the resolution of common distributed computing problems using complex design patterns.
Early sections look at the basics of reading, writing, and searching for data stored in JavaSpaces as well as presenting task and result bags as solutions to managing work done in parallel. The book also elaborates on the readers/writers problem, well-known within the field of computer science, and even offers a means of addressing it. The authors use code samples from a chat message server and a model of a paging system using message channels during their discussion of message passing and communication with JavaSpaces.
One section on distributed patterns presents some common solutions to doing work in parallel, including the Marketplace pattern, illustrated with an e-commerce bidding application. Further sections cover distributed events and transactions as they apply to JavaSpaces. The book closes with two excellent examples, one for a distributed messaging service and another for a brute force attack on encrypted passwords.
With the debut of JavaSpaces, business developers gain access to distributed processing previously available only to academic researchers. The JavaSpaces solution, along with JavaSpaces Principles, Patterns, and Practice, will let any Java developer audition distributed computing for the first time. --Richard Dragan
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