Design And Implementation Of A Web Framework Based On Server Side Push

"Web 2.0" is widely used today and applications based on it soar, in which Ajax plays an important role. It provides the ability to asynchronously communicate to the server, extricating users from the traditional request / response cycle, thereby brings a more natural browsing experience. But through practical development, more and more applications demand the capability of real-time interactions, and a new technology was born in answer to the needs.It is the Comet technology that innovates upon the existing Ajax realization and explores a new world. It has changed the browser from pulling data from the server, and instead the server pushes data directly to the browser. A two-way communication is established between them. Asynchronous events on the server side can be sent directly to the client, and using event-driven architecture the client can immediately respond to the events from server. As a result, applications based on B/S structure become more like as ones based on C/S structure, which was totally impossible to achieve before.This paper discusses the Comet technology in detail, designs and implements a framework using J2EE technology to verify the feasibility of this theory for real-time interactions. I designed my protocol based on Real-Time Streaming Protocol, which contains the concepts of a Control Channel and a Data Channel. Development will focus on both server and client sides: complying with the protocol specified, the server holds and controls the connection to the client, using HTTP Streaming to interchange data. To promote scalability and maintainability, the server framework is divided into four portions per functionalities: Session Management, Event Dispatch, Data Feed and Event Hook modules. On the client side, a JavaScript engine is implemented to send commands, receive streaming data and dispatch events. At last this paper lists several practical applications to examine the reliability and accuracy of the framework, points out some unsolved insufficiency and shortage and proposes some advices for future researches.