【作者】 李会敏；

【导师】 梁艳春；

【作者基本信息】 吉林大学 ， 计算机软件与理论， 2004， 硕士

【摘要】 多层（三层或以上）结构是企业应用系统采用的主流结构。所谓“多层”，就是在原有的“两层结构”（客户端和服务器端）之间增加了多种服务，包括事务处理逻辑应用服务、数据库查询代理和连接适配器等。在多层部署中，表现层、商业逻辑层和数据层各自独立。EJB技术作为Sun公司J2EE企业平台多层结构的主要实现技术而在一段时间内成为多层结构的开发标准之一。另一方面，随着计算机技术日新月异的发展，单台计算机的性能和可靠性越来越好，但还是有许多现实的要求是单台计算机难以达到的。往往需要将多台计算机组织起来进行协同工作来模拟一台功能更强大的计算机来解决问题，这就出现了集群。利用集群技术可以比较容易的搭建高性能、高可靠性、高可用性的服务器。EJB集群比网络层的集群更适合于应用软件系统，比操作系统级的集群成本低易于实现。这种新的集群技术逐渐在大型商用系统中得到广泛的应用。本文研究所应用的云南联通数据综合网管系统就是一个例子。云南联通数据综合网管系统是一个比较综合的大型数据网管系统，造价约800万元人民币。管理云南联通全省16个地州的所有数据网（包括165网、视频会议网、ATM网、VOIP网等）在网设备以及电话交换设备。项目从立项到现今已2年时间，共22人参与研发及工程实施工作，完成代码42万余行。系统已在云南联通运行了半年，取得了很好的效果。本项目中我设计并实现了其中的业务逻辑部分（即消息服务、数据库操作接口、资源管理服务模块），编写代码21787行，安<WP=52>装并部署Weblogic服务器，实现了EJB集群，保证系统的高可靠性和高可用性。本文主要针对EJB集群技术进行研究,第一章介绍了多层结构和集群技术出现的背景以及本文的组织结构。第二章介绍了集群技术和EJB技术，包括集群技术、EJB技术的基本概念和分类以及负载平衡器、一些常用的负载平衡算法。还介绍了J2EE体系结构和EJB框架元素以及结构模型。第三章介绍了EJB集群技术，包括EJB集群概念、EJB集群的负载平衡以及Weblogic应用服务器EJB集群的实现。第四章以云南联通综合数据网管项目为例介绍了EJB集群技术的应用，并对EJB集群技术带来的高可用性进行了验证。描述了业务逻辑模块（中间件系统）的设计和实现过程，即首先设计并实现业务逻辑所需的EJB，然后将中间件服务器集群，并为集群内的每台中间件服务器部署上同样的EJB、消息服务JMS、JDBC连接池和数据源，选择适当的负载平衡算法。本系统还使用了J2EE的JMS（Java Message Service）消息服务来实现整个系统的消息服务，采用的是发表/订阅（Publish/Subscribe）通信模型。第五章对研究进行总结。更多还原

【Abstract】 When the client/server two-tier architecture can not meet the need of the ability of the service management, three-tier architecture comes out. Three-tier architecture adds many services between client and server, including JDBC and transaction. In the three-tier architecture, the representation-tier, the service-tier, the data-tier are independent. On the other hand, with the development of computer technology, the performance of a computer is good enough. But there are many requests that one computer cannot meet. Cluster can resolve this problem.EJB Clustering is a new kind of clustering technology widely used in commercial applications. It is more complicated than network layer cluster and cheaper than cluster at operation system level. The network management System of Yunnan Unicom this research based on is a sample of EJB clustering.The network management System of Yunnan Unicom is a composite data network management system that costs eight million Yuan. It manages all data network devices of Unicom distributed in sixteen regions of Yunnan province .The project costs two year’s hard working of twenty-two software engineers for four hundred and twenty thousand lines of source code. The system has been running for half one year and works well.In this project, I designed and realized the service logic module which including message service, common database operation interface and resource management service module, wrote source code twenty-one thousand seven hundred and <WP=54>eighty-seven lines, installed and deployed the Weblogic server, realized EJB clustering.Chapter1 introduces the background of three-tier architecture and cluster.Chapter2 introduces cluster and EJB，including the concept of cluster and EJB, load balancer, some algorithm of load balance, and the framework of J2EE and EJB.Chapter3 introduces EJB cluster, including clustered EJB and load balance in EJB clustering and the realization of EJB clustering in Weblogic Application Server.Chapter4 describes the process of designing and realizing the network management system of Yunnan Unicom, which uses EJB clustering technology. First we design the EJB that service need. Then cluster servers and deploy the same EJB、JMS、JDBC、DataSource on them. The graphic user interface use EJB manager class to access all EJB. We use Publish/Subscribe type JMS(Java Message Service) to transmit the message which allow different clients to subscribe the concerned topics and read all message of the topic . This system has been running for about half a year in Yunnan Unicom.Chapter5 concludes the research.更多还原