We repeatedly use it in our code for different purposes, but i am still confused where and in which class all abstract method for given interfaces are implemented ? Like setAttribute, getAttribute , removeAttribute , getAttributeNames , getCookies , getContextPath...!
Please explain it in brief with example if posible..! (I am newbie in this technology..!)
That would be in classes that are part of the implementing servlet container. So it's different for each server. If you're interested, get the source code of, say, Tomcat and you'll find the classes that implement those interfaces.