Filter,Dispatcher

Filter:
A filter is a reusable piece of code that can transform the content of HTTP requests,
responses, and header information. Filters do not generally create a response or
respond to a request as servlets do, rather they modify or adapt the requests for a
resource, and modify or adapt responses from a resource.

Dispatcher:
When building a Web application, it is often useful to forward processing of a
request to another servlet, or to include the output of another servlet in the response.
The RequestDispatcher interface provides a mechanism to accomplish this.