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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JavaSpaces™ Principles, Patterns, and Practice

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 system. Example The purpose of this example is to be a walking skeleton of a Jini system. This returns a copy and removes the object tktorial the JavaSpace.

Jini provides both an infrastructure and a programming model. I highly recommend it to students, programmers, and the technically curious.

The full source code is available as a tarball. Clients deal with interfaces. The JavaSpaces05 specification adds support for batch operations. In a production environment, the timeout period specified in the last parameter would be much shorter.

The JavaSpaces model supports a number of design patterns, master-worker being probably the most common. Leases can be renewed explicitly, or implicitly through a lease renewal manager. Image courtesy of Sun Microsystems Those four methods suffice to provide the core features most often required in distributed systems: For simplicity, this example uses my Jini Lookup Utilities to connect to available lookup services and find JavaSpace proxies. The SleepMaster class javapaces a specified number of SleepTask objects to a JavaSpace and then loops until it has retrieved the same number of SleepResult objects.

Jiniology, a series of articles on Jini and JavaSpaces hosted by Artima. With these core Jini services running, you can try out the tutkrial. Stay ahead with the world’s most comprehensive technology and business learning platform. Jini-based systems are described as “network plug and play,” which is a reference to the dynamic, discovery-based nature of interactions between clients and services in a Jini system.


When a lease expires, resources allocated for the service can be freed on both the client and the provider.

Why is the rule thus? Making it a field eliminates a source of error.

JavaSpaces™ Principles, Patterns, and Practice [Book]

And the reason for the private data rule doesn’t apply in this particular case. 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.

When a task is found, the worker removes it from the space, sleeps for the specified duration, and writes a corresponding SleepResult back to the space. Jan Newmarch’s Jini Tutorial. Nobody can accidentally screw up their get and set methods. Unlike JavaBeans, all of the data members of an Entry must be public. Therefore, we asked ourselves, why should we have get and set methods whose behavior is exactly like this other language construct called a field? Please contact me by email if you have any questions, comments, or suggestions.

This, in turn, allows the creation of generic workers that can process any task. Tutoial this javasoaces I want to retrieve any result associated with the current master, so I only specify the masterID.

Patrick May

The code to take tasks from the space looks very similar to the SleepMaster for retrieving results: Removes an entry from the space based on a template. If a particular implementation class is required, it is downloaded transparently. JavaSpace Services with a requirement to share information with other services do so through a Jabaspaces.

The JavaSpace version of a Linda tuple is called an entry and described by the net.

The code to take results from the space is: Why not just make it a field? Using the space as a means of communication and synchronization simplifies distributed design and development as opposed to something like direct RPC [Remote Procedure Calls] or inter-node message passing. Those four methods suffice to provide the core features most tuyorial required in distributed systems: With Safari, you learn the way you learn best.


Location Independence Components that use services do not need to be configured with explicit knowledge of the location of the service. Running The Example Any number of masters and workers can be started in any order. This prevents resource accretion, a common problem in distributed systems. Leases on a service can be shared or exclusive.

When a lease expires, the resource is recovered and made available to other components. Building You will need the Jini 2. As part of the fruits of Sun’s Jini project, we now have the JavaSpaces technology, a wonderfully simple platform for developing distributed applications that takes advantage of the power of the Java programming language.

This arrangement is sometimes referred to as the Master-Worker or Compute Server pattern. SleepWorker uses the same utilities to find transaction manager proxies as well. Jini belongs in the virtual toolbox of anyone building distributed systems in Java.

Deploying the Jini infrastructure is considerably less straightforward than building the example. The lookup utilities are in a separate tarball. But we’re not a very religious bunch.

JavaSpaces is described in a Sun Microsystems specification as part of Jini, and a reference implementation called Outrigger is distributed with the Jini Javaspacds Kit. For those tutoriak with Linda, an entry differs from a Linda tuple in that it is strongly typed and may contain behavior methods in addition to data attributes.