A ServletRequestListener can be implemented by the developer interested in being notified of requests coming in and out of scope in a web component.
A request is defined as coming into scope when it is about to enter the first servlet or filter in each web application, as going out of scope when it exits the last servlet or the first filter in the chain. what does mean to the bold line?? filter chain is responsible for calling next filter or a resource (servlet or JSP) accodring to the mapping in DD. we pass request and response object while calling doFilter method on FilterChain object. like FilterChain.doFilter(request,response).
then how can a request become OUT OF SCOPE when it exits from the first filter from the chain??
Well I think you are confused here. The first filter in the chain is the filter which is executed 1st when a request enters the web application and is also executed last when a response exits the web application. Don't think the first filter in the chain as the first one which gets executed after the last servlet. This is just a confusion due to terminology. The first filter in the chain is executed as the last filter when the response is sent to the client...