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JavaSpaces is a powerful Jini service that provides a high-level tool for creating .. In a tutorial style, we cover the mechanics of creating a space-based. Selection from JavaSpaces™ Principles, Patterns, and Practice [Book] access to videos, live online training, learning paths, books, tutorials, and more. If you want more detail, I recommend Jan Newmarch’s Jini Tutorial. A JavaSpace is a Jini service that stores Java objects in memory. This makes it very useful.

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Therefore, we asked ourselves, why should we have get and set methods whose behavior is exactly like this other language construct called a field? In this case I want to retrieve any result associated with the current master, so I only specify the masterID.

Introduction to Jini and JavaSpaces | Jini and JavaSpaces: Enabling the Grid | InformIT

Summary Jini provides some unique benefits for addressing the difficulty javasaces in building, deploying, and managing distributed systems. Image courtesy of Sun Microsystems The master-worker pattern is javas;aces in a wide variety of problem javxspaces where either a problem is highly parallelizable or there are a set of tasks that can be performed by any of a set of workers. Jini supports the development and deployment of highly available, highly reliable distributed systems despite the unreliability of the underlying machines, operating systems, and networks.

Now this sometimes makes people uncomfortable because they’ve been told not to have public fields; that public fields are bad. I highly recommend it to students, programmers, and the technically curious.

The only public data members exposed are those required for the template-based matching of the JavaSpaces API.

This makes it very useful for supporting collaboration among other javas;aces, in addition to its uses as a simple shared memory. The Jini programming model extends the core Java classes to include semantics for distributed computing.


A variant of the master-worker pattern takes advantage of the fact that a JavaSpace holds full Java objects, not just data. An Introduction to Jini L. Making it a field eliminates a source of error. Leases on a service can be shared or exclusive. And often, people interpret those things religiously.

This book introduces the JavaSpaces architecture, provides a definitive and comprehensive description of the model, and demonstrates how to use it to develop distributed computing applications. Worker and is subject to the same caveats with respect to production. All objects that can be stored in a JavaSpace must implement the Entry interface. View table of contents. These core services include service registration and lookup, distributed event notification and messaging, principal and access control list security, and a model for distributed transactions.

JavaSpaces can, however, serve as an enabling technology for a class of useful services implemented on a grid. A Jini lease grants access to a service for a certain time period and can be renewable. The JavaSpace version of a Linda tuple is called an entry and described by the net.

Patrick May

Lookup Service The lookup service, named reggieis the first among equals of Jini services. The SleepWorker class loops, performing a blocking take for SleepTask objects. The code to take results from the space is: Leases futorial be renewed explicitly, or implicitly through a lease renewal manager. One particularly nice feature of this pattern is that there is no need for complex scheduling algorithms. The standard Jini services are: Chief among these are the ability to self-heal, the prevention of resource accretion, and the simple programming model that comes from decoupling the logical components from the physical topology of the javasaces.

This arrangement tutoral sometimes referred to as the Master-Worker or Compute Server pattern. The JavaSpaces associative blackboard-style system provides a very simple mechanism for communication between the nodes in a distributed system. Another key concept of the model is embodied by the lease interface, which incorporates the notion of time into a reference to a non-local object.


It provides a necessary ubiquitous, cross-platform framework for distributed computing, emerging as a key technology in this expanding field. Those four methods suffice to provide the core features most often required in distributed systems: JavaSpaces lends itself to blackboard-style processing, in which specialized processes take rutorial from the shared board, perform their function, and then return results to the shared memory space. Several initiatives are under way to javaspacss the core Jini services to provide further grid-like functionality, such as scheduling and wide-area service discovery.

It is now being continued under the auspices of the Apache River project.

All resources in a Jini system are leased, including proxy records in the lookup service, transactions, and, of course, memory in a JavaSpace.

Nobody can accidentally screw up their get and set methods. A tuple in the space is a vector of data values.

JavaSpaces™ Principles, Patterns, and Practice [Book]

Why not just make it a field? Writing the result back mirrors the initial task write, again with the addition of a transactional context: Clients to a JavaSpace can use it to javaspacrs information, including divisions of a problem that can be solved in a distributed and parallel fashion.

This programming model is based on a set of interfaces defining public requirements for behaviors such as transactionality across nodes and distributed event subscription and notification. We sat back and asked: On their own, the concepts behind JavaSpaces are neither directly related nor limited to grid computing.

Any number of masters and workers can be started in any order.