A.Yourfilterclassmustimplementaninitmethodandadestroymethod.
B.Yourfilterclassmustalsoimplementjavax.servlet.FilterChain.
C.Whenyourfilterchainstothenextfilter，itshouldpassthesameargumentsitreceivedinitsdoFiltermethod.
D.Themethodthatyourfilterinvokesontheobjectitreceivedthatimplementsjavax.servlet.FilterChaincaninvokeeitheranotherfilteroraservlet.
E.YourfilterclassmustimplementadoFiltermethodthattakes，amongotherthings，anHTTPServletRequestobjectandanHTTPServletResponseobject.