| Researches on J2EE architecture start from the Web technology developing,today when the web technology develops very fast,the C/S structure can't satisfy the system any more,then the structure of software start to tranform to B/S.Under the structure,UI is implemented by WWW browser,client only store present-tier software,application logic including transcation processing,controlling,message queueing,Web Service etc are processed by special middle-ware server,the background is RDBMS.In multi-tier distributed structure,the system resources are managed and used centerly,user can use the network resource transparently by the portal.Followed by Windows 98/Windows 2000 embed the IE technology into OS,the structure will be the principal choice. With the development of WEB techonoly,it results in the E-commerce appearance,every departments need co-operation in society more and more.The key technology of developing enterprise application program is needing a power and flexible architecture.J2EE can do this.Now the researches on the J2EE architecture prevail by the time passed. What the researches on the J2EE architecture concentrate on: (1)WEB-TIER development method,popular method is MVC pattern at present.The patterns based on MVC pattern mainly have Structs WebFrame,Spring WebFrame,WebWork WebFrame ect.These webframes can separate the present-tier from the business-tier,so the present-tier only has little JAVA code. (2)Based on components development,J2EE components are commonly deployed into application server. Development Based on componentscan improve the resource reuse effectively,make the release controlsimpler,can improve the development efficiency,make the debuy conveniently. The main components are EJB,mainly include SessionBean,Entity Bean (3)Persistence of data.The main methods includes DAO(Data Access Object),JDO,Hibernate. (4)The development patterns in every tier.These patterns can help the developer in solving the enterprise problem,voiding the mistakecommited by others,quicked the developing progress,improve the softwarequality. In the paper we introduce the evolution course of software structure ,from the C/S to B/S,analysis both advantages and disadvantages,analysis the use domain.Now the application based on WEB make the structure will be the principal choice. In the paper wo introduce the basic conception about J2EE,such as:EJBcomponent,architecture,pattern. Next we introduce tier-partition about J2EE,architecture character,basic realization based on tiers,design pattern on every tier and webframe.The tier-partition is based on J2EE criterion,considering the software reuse thoughtfully,maintainability,safety,and expansibility.It partitions the structure into five tiers:client tier,present tier,business tier,integration tier and resource tier.Each tier completes distinct function.In client tier,mainly processes user interaction .Present tier responses the WEBclient request,receives and verifys the input data,transfers the data to business logic components in the business tier,and returns the resultto user.Business tier receives the data from the client program,does some processes,then transfers them to EIS tier.On the other hand,it also answers for retrieve data from storage,and transfers the data to client.Integration tier is responsible for data encapsulation.EIS tier mainly is RDBMS.The system realization is like this:in web tier,we adopt MVC pattern,combine Service to Worker,FrontControl,ViewHelp pattern.Start from the access to JSP,then process by Control tier,if need complicated business logic transaction and has background realization(EJB etc.),by the Business Delegate tier,access background business logic process.Business logic tier uses the Facade pattern to encapsule into a unified interface,business logic tier realizes complicated transaction,if need to access the resource tier,then through the DAO tier to access the resource(mainly RDBMS,sometimes legacy system,such as Corba,JMS,WebService,SAP etc.) In the paper we introduce design patterns about ea...
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