Servlet Filtering
Filters are a feature that was introduced in version 2.3 of the servlet specification. A filter is a special type of servlet that dynamically intercepts requests and responses and transforms the information contained in them. The main advantage of a filter is that it can be added to existing applications without any need for recompilation.
Filters can have several important uses:
To encapsulate recurring tasks in reusable units
To format the data sent back to the client
To provide authorization and blocking of requests
To provide logging and auditing
A filter can perform filtering tasks on the request, the response, or both.
Programming Filters
A filter is still a servlet, so it extends HttpServlet but it also implements the
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