how to push the data to the jsp with out requesting it for every 2 seconds?

Question

I want to push the data to the jsp for every 2 seconds, with out client requesting it.
I am using Spring with Hibernate here.
I am displaying google maps marker, and I want to update the marker location for every 2 seconds by getting the data from database, however I have done getting the data from database for every 2 seconds, but I am unable to push that data to this jsp.

   @Scheduled(fixedRate = 2000)
   public void getData(){
                    // TODO Auto-generated method stub
                    DeviceDetails deviceDetails = realTimeDataDAO.getDeviceDetails(deviceId);
                    System.out.println(deviceDetails);
                }

I have to display some data after every 2 seconds. Can anyone tell me how to do that?

any one knows about Comet Ajax Push technology, will it work in this scenario?

Answer 1

You have a number of choices.

Polling - as mentioned in other answers you could simply have javascript in the client constantly poll the server every 2 seconds. This is a very common approach, is simple and will work in the large majority browsers. While not as scaleable as some other approaches setup correctly this should still be able to easily scale to moderate volumes (probably more users than you'll have!).

Long polling - Also known as Comet this is essentially a long lived request. The implementation of this will vary depending on your app server. see here for Tomcat: http://wiki.apache.org/tomcat/WhatIsComet or Jetty bundles some examples.

HTML 5 solutions while the web is traditionally request response based - event based processing is part of the HTML 5 spec. As you events seem to be only one way (server -> client) Consider using Event sources. See: http://www.html5rocks.com/en/tutorials/eventsource/basics/ or again the Jetty examples. Caveats here are that only modern browsers and some app servers support these methods - e.g. Apache doesn't natively support websockets.

So to sum up - my gut feeling is that your needs and for simplicity a polling approach is fine - don't worry too much initially about performance issues.

If you want to be on the cutting edge, learn new thing and you have control over your app server and frameworks then I'd go for the HTML 5 approach.

Comet is kind of a half way house between these two.