ramya srei

one could say here in general context means

"the circumstances that form the setting for an event, statement, or idea, and in terms of which it can be fully understood and assessed."

in the same way context in respect to servlet means an object that can to some extent give information on attributes related to the servlet, its initialization and application to which the servlet is associated with etc.

you could use synchronized get/set methods or processing methods to access the instance variables

please read
http://docs.oracle.com/javaee/5/tutorial/doc/bnafo.html#bnafs

you could use filters to intercept response after commit to gain back the control

Please follow the link for more info on how to intercept the response using custom response http://docs.oracle.com/javaee/5/tutorial/doc/bnagb.html