I got the solution with the help of JFA,
In short, The following snippet of code will enable to post/push message to channel in the Context.
String message = "<<Your message>>";
String user = "<<who am I>>";
HashMap<String, Object> map = new HashMap<String, Object>();
map.put("chat", message);
map.put("user", user);
Data data = new Data();
data.setMapData(map);
data.setChannel("/chat/demo");
data.setClientId("ejb6312");
CometEngine cometEngine = CometEngine.getEngine().getCometContext(contextPath).notify(data);
Note: HashMap and Data is a wrapper to create a bayeux message of the following form
/*[{"successful":true,"channel":"/chat/demo","timestamp":"Wed, 30 Apr 2008 15:43:34 GMT","id":"5"},{"id":"5","timestamp":"Wed, 30 Apr 2008 15:43:34 GMT","data":{"chat":"<<Your message>>","user":"<<who am I>>"},"channel":"/chat/demo"}]*/. For more information please look at bayeux spec and JFA's dojo chat application.
Please look at the below link for more details
http://forums.java.net/jive/thread.jspa?messageID=272256񂞀
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http://forums.java.net/jive/thread.jspa?messageID=272263