J2EE Lightweight Framework Construct Instant Messaging System

Instant Messaging is currently the most popular way to communicate on the Internet. As most Instant Messaging system used in personal entertainment and leisure, web IM is adopted by many enterprises and businesses. The using of Web IM improves the efficiency and reduces communication costs. Although, Instant Messaging will play a more and more important role in the age of web2.0, the current system implements simply and the hierarchical structure is not clear. Therefore the system is not flexible and scalable for maintenance.So, in this thesis, a Instant Messaging System based on lightweight J2EE framework which is elegant,effective,and reliable was proposed. It is a N-tier architecture of J2EE platform architecture,using Hibernate,Spring and DWR. The features are as follows:(1) The project integrates the Ajax technology in the J2EE platform. We use a open -source framework--DWR for the development of Ajax, DWR enable JavaScript code can directly access Java methods, and eliminate all Ajax request-response cycle from the application code, the procedure takes only about logic.(2) The core business logic tier adopts the spring framework. With the mechanism of IoC, it reduces coupling, and the thinking of AOP make transaction more effective. Hibernate O/R mapping with responsibility for data persistence. The system is flexible,scalable and maintainable because the integration of spring and hibernate framework.(3) The system adopts the MVC model, and it make the business logic,presentation and control isolate. So it is flexible.The thesis introduces the principle of IM firstly,and then,I describes the develop method. With following,I introduces the Hibernate framework,the Spring framework,and the DWR framework which are adopted in the Instant Messaging System. After that,the thesis gives details of the design and implementation of the system. Finally,the thesis poses the problems which need future study.