What is filter? Can filter be used as request or response?
Servlet Filters are the latest components that are added in Servlet 2.3 specifications. These filters are used basically for intercepting and modifying requests and response from server.Consider a scenario where you want to check session from the every users request and if it is valid then only you want to let the user access the page. You can acheive this by checking sessions on all the servlet pages (or JSP pages) which users queries or you can do this by using Filter.