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•Servlet Callback method ??

Posted on 2004-08-15
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Last Modified: 2013-12-10
•why we say that the followings are Servlet Callback method ?
–doGet
–doPost
–Init
–Destroy

why we use the word "callback".

thanks
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Question by:she1
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3 Comments
 
LVL 23

Expert Comment

by:rama_krishna580
ID: 11807028
Hi,

A callback method is a method intended to be passed as a parameter. The callee can then call the passed method asynchronously and with whatever parameters it deems appropriate. Callbacks are often used in event handling code.

R.K
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Expert Comment

by:damonf
ID: 11825012
as RK says, a callback method is designed to be called asynchronously.  That is, if object A owns method callback(), and object A enlists object B to perform some work, object B may later call a.callback() with the result of the work.  Object A does not need to maintain a reference to B for this to happen.

doGet and doPost are callbacks because any HTTP client can call them any time.  Init() and destroy() are callbacks because the container can call them anytime if it wishes to start and stop the servlet.  Actually doGet and doPost are really called by the container as well (in reaction to the client's HTTP request).  But they still can be called any time.
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Accepted Solution

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fschutte earned 120 total points
ID: 11907693
they are simply callback methods because they are invoked by the container (every container managed component has callback methods because that's the way to communicate with the container)
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