Sunday, February 16, 2014

Non HTTP initiated broadcast with Atmosphere framework

In this blog post I would like to show you how you can push server side events to a web application using the atmosphere framework. I will also show how you can broadcast to a set of AtmosphereResource instances, not to all suspended connections. If you want to jump right to the code have a look at my github account.

In this simple example the backend will notify the front-end about the following three events

In order to demonstrate the selective broadcast functionality we will broadcast ACCOUNT_DEBITED to chrome, ACCOUNT_CREDITED to firefox and ACCOUNT_LOCKED to IE browser clients. In real application you would broadcast the event to the currently logged in user whose account was debited, credited or locked.

On the front-end with the help of atmosphere.js I send as a header the information about the client (currently the type of the browser)

The initial transport is set to websocket, however if the browser or backend doesn't support it, it will fall back transparently to long polling. The subscribe function initiates a GET request which is handled by the following managed service

With a camel timer component we simulate the continuous event generation. The events are broadcasted to the appropriate AtmosphereResource which models a connections between a client and the server.

With the help of atmosphere framework the events are pushed via websocket or long-polling transport. As you can see below with IE 9 the transport will be long polling since it does not support websockets. With chrome or firefox websocket transport will be chosen.


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