The Design And Realization Of Multi-tier Distributive System Structure Based On J2EE And EJB

The traditional C/S model has been popular for a long time . It ever was a successful solution to enterprise computer. Howerver Since 1990s, With the application on Intenet becoming more and more widely and Internet technology being more and more advanced , the tradition C/S model appears obviously not to meet the development requirement of moden enterprise application, the original computer architecture has developed from the 2-tied C/S architecture to the 3-tied C/S . The 3-tied C/S equals to adding a new Logical tier梐pplication tier between client tier and server tier .which makes the business logic separated out from client tier, and then merges storage procedure in database to form application tier. The application tier can decrease the code quantity in client , and focus to manage the business logic . Therefore , the multi-tier system must has the following features: distributed, well-scaled, retractable and secure .J2EE platformreleased by SUN fully meets the development of modern enterprise application.It not only inherits platform-independent feature of Java language , but also combines component technology. It provides modem enterprise with a integrated solution to establish distributed application rapidly. Based on the upgrade item of accountant work competence management in Hangzhou finance department , This paper focuses on the design and realization of EJB-Based 3-tied C/S struture: Three distributed-transact technologies (RMI, CORBA, COM) has been deeply discussed. The Component-Based technology of J2EE framework , EJB , is compared with the COM+ teachnology of Windows DNA framework in several aspects . At the same time J2EE platform technologies are discussed deeply, such as J2EE platform technologies , communication technologies, EJB component technologies and so on . the design model based on the MVC frame is applied in the system development, so that the separation between the present logic and the business logic in the application is realized . Finally, according to the problemsfound in the development process, the paper explains particularly the kay technologies in the realization: The uniform Naming Service is realized by realizing the Service Locator partten Using the Value Object Pattern, All the status data is encapsulated into a serializable Object, then transferred among the Client, SessionBean and EntityBean in order to decrease the potential Network traffic caused by reference of EntityBean; In order to improve the performance of data storing and taking , we introduce the FACADE model to escapsulate the EJBs which delegate the data model .Weblogic application server of BEA Corporation is chosen as the deployed platform. The 3-tied C/S application based on the EJBs is realized with the Jbuilder of Borland Corporation.