Wrapper, Filter and Servlet -

since new servlet programming, possible ask basic question.

i writing application filter gets response servlet, , computation it. found out need wrapper class catch response.

my question why wrapper needed? in advance!

1) lets first understand how request , request filter work:

when, lets client, makes request servlet, goes through container. container decides servlet request needs forwarded to. means, container in total control.

container control makes implementing request filter easy because can let container know request should go filter first , servlet. because container in total control. implementing request filter easy.

2) lets understand how response , response filter work:

when container invokes servlet service methods, passes 2 objects methods, request , response.

this means servlet in total control send response client. how ?

because response object has pointer output stream writer object. means, once servlet finishes processing request, straight write response client using pointer output writer stream object. so, servlet won't wait (middle men filter) , straight serve client. time, late intervene.

so, what's solutions ?

wrapper our solution.

how wrapper works ?

so, before container passes real request , response objects servlet, wrap our response object , send real request , wrapped response objects servlet service methods.

so now, servlet has pointer our wrapped output stream writer object , not real response output stream writer object. so, when servlet finishes request, write response our wrapped stream , our wrapped response object write real response writer stream.

moral of story: use wrapper when dealing response. request doesn't need wrapper concept.