The Web messaging service brings Web-based publish and subscribe messaging to the application server and the browser. With Dojo Toolkit support,
no browser plug-ins are required to receive server sent messages. Incoming messages tie into the Dojo topic/event system for easy integration into existing Dojo enabled Web pages.
Communication from the browser to Web messaging service occurs through the Bayeux protocol. The Web messaging service is the comet or Asynchronous JavaScript and XML (Ajax) push implementation. Traditionally HTTP polling is used for to receive messages from a server; however, the comet pattern implements a server push model.
This typically involves keeping an HTTP request open for small duration to wait for server to receive messages.
A Web messaging utility library can effectively be inserted to any new or existing Java 2 Platform, Enterprise Edition (J2EE) application used with the application server. Scalability is achieved through a new Websphere Application Server runtime library that uses the channel framework
to avoid consuming a Web container thread for each outstanding request, enabling the Web messaging service to scale. A bridge to platform messaging supports connectivity to the service integration bus. This bridge enables a wide range of resources to publish messages to Web messaging clients.
Figure 1: Server Architecture: