ilter that it is being taken out of service.
 </p>

 <p>
 This method is only called once all threads within the filter's doFilter method have exited or after a timeout period
 has passed. After the web container calls this method, it will not call the doFilter method again on this instance of
 the filter.
 </p>

 <p>
 This method gives the filter an opportunity to clean up any resources that are being held (for example, memory, file
 handles, threads) and make sure that any persistent state is synchronized