dimanche 29 décembre 2013

HTML 5 Server Sent Events on Glassfish 4

SSE (Server Sent Events) is a Web Pushing technology which was developed under HTML 5 technology. So, what is Pushing?

It is a transmission of data sets which of them are sent at regular intervals or in any time through the server application, in the direction of server – – – >browser, without need for any request of web browser. Serving Twitter updates currently in the web page at regular intervals, appearance of Facebook shares on screen when a new share is available, serving instant financial data (exchange rate of dollar, parity etc.) immediately to users’ screen can be given as examples for pushing scenerio.

Server Sent Events is not a unique technique used for pushing of http resource, in theprevious article, we mentioned how to provide data transmission to the web browser by LongPolling technique. I think this sequencing about Push technologies would not be wrong generally in this order;
Polling –> LongPolling –> ServerSent Events –> WebSocket
ServerSent Events is a technology that its developments is already continues, such as WebSocket technology. For this reason, I would like to mention that it is not useable in every web browser and that’s for sure it is supported by new generation web browsers.

SSE technology has a few additional features unlike other ones, such as automatic connection recovery when the connection is lost, routing the message to an certain function in event/resource broadcasts. For example, you can take a look at to the discussion about the comparison of SSE and WebSocket from the entry in StackOverFlow.
How the SSE works?
The logic of operation of SSE technology can be seen in the picture illustrated below. Ahandshake request is sent to SSE supported server by the web browser and server system returns a handshake response which is “text/event-stream” MIME type. After the handshake committed among web browser and SSE service, SSE service may send any amout of data at any time. jaxrs-sse