Jini网络技术介绍(Technology Computer English)

 
[align=left]Jini -- a technical specification developed by Sun[/align]
[align=left]Microsystems that uses a small piece (48K) of Java code to[/align]
[align=left]allow any network device with a Java virtual machine (JVM)[/align]
[align=left]to announce its availability and provide its services to any[/align]
[align=left]other device connected to the same network. Jini is based on[/align]
[align=left]the concept of creating a "federation" of self-configuring[/align]
[align=left]devices capable of transparently exchanging code when necessary[/align]
[align=left]to simplify interactions between network devices.[/align]
[align=left]Jini network technology provides simple mechanisms which[/align]
[align=left]enable devices to plug together to form an impromptu community[/align]
[align=left]-- a community put together without any planning,[/align]
[align=left]installation, or human intervention. Each device provides[/align]
[align=left]services that other devices in the community may use. These[/align]
[align=left]devices provide their own interfaces, which ensures reliability[/align]
[align=left]and compatibility.[/align]
[align=left]Jini technology uses a lookup service with which devices[/align]
[align=left]and services register. When a device plugs in, it goes[/align]
[align=left]through an add-in protocol, called discovery and join-in.[/align]
[align=left]The device first locates the lookup service (discovery) and[/align]
[align=left]then uploads an object that implements all of its services'[/align]
[align=left]interfaces (join).[/align]
[align=left]To use a service, a person or a program locates it using the[/align]
[align=left]lookup service. The service's object is copied from the lookup[/align]
[align=left]service to the requesting device where it will be used. The[/align]
[align=left]lookup service acts as an intermediary to connect a client[/align]
[align=left]looking for a service with that service. Once the connection is[/align]
[align=left]made, the lookup service is not involved in any of the resulting[/align]
[align=left]interactions between that client and that service.[/align]
[align=left][/align]
[align=left]Jini是一种由Sun Microsystems公[/align]
[align=left]司开发的技术规范它使用小块Java代码[/align]
[align=left](48KB)就能在任何具有Java虚拟机JVM[/align]
[align=left]的网络设备上运行并为连接至相同网络[/align]
[align=left]的其它设备提供服务Jini规范是基于创[/align]
[align=left]建自配置设备联盟的概念这些自配[/align]
[align=left]置设备在需要简化网络设备间的交互作用[/align]
[align=left]时能透明地交换代码[/align]
[align=left]Jini网络技术提供了简单的体系该[/align]
[align=left]体系能够使设备插接在一起以形成临时工作[/align]
[align=left]组即不经过任何规划安装或人工干涉[/align]
[align=left]而连接在一起的工作组每台设备都能提供[/align]
[align=left]服务工作组的其它设备也可以使用这些服[/align]
[align=left]务这些设备有他们专用的接口这就保证[/align]
[align=left]了体系的可靠性和兼容性[/align]
[align=left]Jini技术使用查询服务设备和服务[/align]
[align=left]利用查询来注册当接入一台设备时必[/align]
[align=left]须通过一个名为发现和加入的附加协议[/align]
[align=left]首先该设备寻找查询服务的地址发现[/align]
[align=left]然后上载能够实现所有服务接口的对象[/align]
[align=left]加入[/align]
[align=left]要使用服务首先必须利用查询服[/align]
[align=left]务程序来对程序确定地址将服务对象[/align]
[align=left]从查询服务复制到将使用服务的应答设[/align]
[align=left]备查询服务作为媒介来连接寻找服务[/align]
[align=left]的客户和该服务一旦建立连接查询服[/align]
[align=left]务就不再介入产生交互作用的任何客户[/align]
[align=left]端和服务器[/align]
[align=left][/align]
[align=left]It doesn't matter where a service is implemented --[/align]
[align=left]compatibility is ensured because each service provides everything[/align]
[align=left]needed to interact with it. There is no central[/align]
[align=left]repository of drivers, or anything else for that matter.[/align]
[align=left]The Java programming language is the key to making[/align]
[align=left]Jini technology work. Devices in a network employing[/align]
[align=left]Jini technology are tied together using Java Remote[/align]
[align=left]Method Invocation (RMI). By using the Java programming[/align]
[align=left]language, a Jini network architecture is secure. The[/align]
[align=left]discovery and join protocols, as well as the lookup[/align]
[align=left]service, depend on the ability to move Java objects,[/align]
including their code, between Java virtual m
4000
achines.
[align=left]Jini technology not only defines a set of protocols[/align]
[align=left]for discovery, join, and lookup, but also a leasing and[/align]
[align=left]transaction mechanism to provide resilience in a dynamic[/align]
[align=left]networked environment. The underlying technology and[/align]
[align=left]services architecture is powerful enough to build a[/align]
[align=left]fully distributed system on a network of workstations.[/align]
[align=left]And the Jini network infrastructure is small enough[/align]
[align=left]that a community of devices enabled by Jini network[/align]
[align=left]software can be built out of the simplest devices. For[/align]
[align=left]example, it is entirely feasible to build such a device[/align]
[align=left]community out of home entertainment devices or a few[/align]
[align=left]cellular telephones with no "computer" in sight.[/align]
[align=left][/align]
[align=left]在哪里实现服务其实并不重要因为[/align]
[align=left]每个服务提供了用来交互的所有信息所以兼[/align]
[align=left]容性得到了保证不存在驱动程序的中心储存[/align]
[align=left]库或与此相关的其它因素[/align]
[align=left]Java编程语言是完成Jini技术工作的[/align]
[align=left]关键所在在一个网络中通过Java Remote[/align]
[align=left]Method Invocation (RMI)将应用Jini技[/align]
[align=left]术的设备紧密联结在一起使用Java编程语[/align]
[align=left]言就保证了Jini网络体系结构的安全发[/align]
[align=left]现和加入协议同查询服务一样都有能力在[/align]
[align=left]Java虚拟机之间移动Java对象或者代码[/align]
[align=left]Jini技术不仅定义了发现加入和查询的[/align]
[align=left]一整套协议而且还确定了一套能够在动态网[/align]
[align=left]络环境下具有弹性的事物处理机制底层技术[/align]
[align=left]和服务机制足够强大可以用来在网络工作站[/align]
[align=left]建造完全的分布式系统[/align]
[align=left]同时Jini网络基础结构是如此之小以[/align]
[align=left]致于用最简单的设备就可以建造出由Jini网络[/align]
[align=left]软件激活的设备工作组例如在视野中没有[/align]
[align=left]计算机的情况下仅仅通过数台家庭娱乐设[/align]
[align=left]备或几个蜂窝电话就可以建造出一个设备工[/align]
[align=left]作组这样的方案是完全可行的[/align]