is there any function in java servlet which will trigger a response at a particular time like for eg. we have a time 3:00pm in a database and then can we send a pop up window or an email telling that its 3:00 pm .
A servlet? No. The web runs in a request-response transactional mode and what you seem to be asking for would be the equivalent to an unrequested response. A non-web application can do that with ease.
sounds like a not too good idea. I think an option may be that you have an applet in the page where you want to create a popup.
Then create a thread that keeps connection between the server side app and aplet open and then make ur applet do the task when required..hope it made some sense...