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Jini in Software Implementation qrcode in Software Jini

Jini generate, create qr code 2d barcode none with software projects EAN/UCC-13 The methods getLocalContent( Software Quick Response Code ) and getRemoteContent() return a list of available local or remote content. A program usually calls these methods after being noti ed of content changes. The startSearch(String searchString) performs a search for remote data that can be restricted by the searchString argument if the searchString is not null.

Again, note that this is an asynchronous method that returns immediately and the result of the search is delivered at the end of the operation to the registered ContentListener objects.. JINI JXTA is not the only way to qr barcode for None build network architecture as a dynamic, living organism. Another example is Jini..

Jini provides us in the cont ext of being able to put objects anywhere, the ability to move them around and to do a few other things that you need to do once you have true distributed computing. But the bigger picture here, this pervasive object computing, is that the ability to put systems on single chips with pervasive wired and wireless networking . .

. . Bill Joy on Java and Jini, from presentation transcript [3].

. Jini is a way of building a Software QR Code federation of network-centric services, creating an adaptive, scalable, and dynamic computing environment. The Jini architecture uses objects that move around the network. Jini allows each object-service to adapt to network changes.

The Jini API and network protocols specify how object-clients nd service providers, how objects work together toward a common task. Jini builds distributed object systems service federations. A service federation combines application-based and infrastructure-based services and makes the services available to a (privileged) user.

A service object can announce its presence and capabilities on the network. (Does it look like JXTA advertisements Yes! But remember, Jini actually was the rst on that block.) The client uses a lookup service (part of the Jini core infrastructure) to nd a desired service on the Internet.

Service objects can join and leave federations at run-time. When joining the federation, a service registers for a lease period with a Registrar object. Because only current services can be discovered, the service should renew its lease periodically.

Jini assumes that network services are very dynamic; they can die and be restored at any time. That s why there is no such thing as a permanent service everything is temporary or leased. Jini widely uses the Factory and Abstract Factory design patterns to construct objectservices on the y.

For example, the net.jini.jeri.

AbstractILFactory class implements the InvocationLayerFactory and the interface provides a convenient way for subclasses to create proxies and invocation dispatchers for remote objects. Jini has a provision for privilege-based access to services. For example, the AccessPermission class represents permission to call a method.

Jini deals with a typed collection of objects called Entry. The net.jini.

Entry.AbstractEntry class is a generally useful base class for entry types. The net.

jini.core.entry.

Entry interface represents service-speci c attributes for example, in the Jini lookup service and JavaSpace. DISTRIBUTED LIFE IN THE JXTA AND JINI COMMUNITIES interface to mark entries. E qr barcode for None ntry elds are public, nontransient, nonstatic, and non nal, and must be objects (nonprimitive). The Entry types have a public, no-argument constructor that ts perfectly into the magic formula for dynamic class loading:.

Class.forName(name).newInsta nce().

The Entry types are polymorp QR for None hic value objects that create a highly extensible one-type system. (A similar example of typed collections was provided for the Topic Maps implementation in 5 and for several document types in the document-handling application described in 6.) The interface to the lookup service is de ned by the ServiceRegistrar.

Implementations of the lookup service export proxy objects that implement the ServiceRegistrar interface locally to the client. This makes the ServiceRegistrar a local interface that can use an implementationspeci c protocol to communicate with a remote server. One should implement the ServiceRegistrar interface to work with registered services.

There are several methods that constitute the service registration mechanism: void addAttributes(Entry[] attrSets) adds the speci ed attribute sets (those that aren t duplicates of existing attribute sets) to the registered service item Lease getLease() returns the lease that controls the service registration, allowing the lease to be renewed or canceled ServiceID getServiceID() returns the service ID for this service void modifyAttributes(Entry[] attrSetTemplates, Entry[] attrSets) modi es existing attribute sets void setAttributes(Entry[] attrSets) deletes all of the service item s existing attributes and replaces them with the speci ed attribute sets The net.jini.core.

lookup.ServiceTemplate instances help match items in the lookup service. There are several attributes that must match: serviceID, service (name), and serviceTypes.

The attributeSets should contain at least one matching entry for each entry template (in attributeSetTemplates). An entry matches an entry template if their classes (or superclasses) match and every non-null eld in the template equals the corresponding eld of the entry. Every entry can match more than one template.

Note that in a service template, for serviceTypes and attributeSetTemplates, a null eld represents a wild card. Theoretically, the Jini API and protocols can be implemented in any language. A current practice, however, uses Sun Microsystems implementation with Java language and Java Remote Method Invocation (RMI) as a client server communications protocol.

Most of the proxy methods have normal RMI remote interface semantics. Jini services represent a wide range of service concepts, including printing and storage. The most popular Jini service is JavaSpaces, which provides a distributed persistence mechanism for Jini entries.

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