Question: 1 What is a servlet filter? Ans: A filter dynamically intercepts requests and responses to transform or use the information contained in the requests or responses. Filters typically do not themselves create responses, but instead provide universal functions that can be "attached" to any type of servlet or JSP page. Filters provide the ability to encapsulate recurring tasks in reusable units and can be used to transform the response from a servlet or a JSP page. Filters can perform many different types of functions: * Authentication * Logging and auditing * Data compression * Localization The filter API is defined by the Filter, FilterChain, and FilterConfig interfaces in the javax.servlet package. You define a filter by implementing the Filter interface. A filter chain, passed to a filter by the container, provides a mechanism for invoking a series of filters. Filters must be configured in the deployment descriptor : <!--Servlet Filter that handles site