Filters

[sangeeta kapoor]

Page 699 HF Servlets and JSP
Ques 5

Which about Filters is true


A. Filters may be used to create request and response wrappers.
B. Wrappers may be used to create request or reponse filters

Shouldn't B be correct instead of A
Correct Ans given in book is A

[alzamabar]

I also had the same problem the first time, then I understood. Thanks to filter, it's possible to create a 'wrapper' around a request/response objects. Filters use wrappers but it's not the other way round. Think of a filter to compress the response. The filter uses the HttpServletResponseWrapper class to actually pass behind the scenes a custom response object whose getOutputStream() method returns a custom output stream in gzip format. It's the filter which knows about the wrapper and not the other way round.

Hope this helps