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Confused about Life cycle of Servlets

pawan chopra
Ranch Hand

Joined: Jan 23, 2008
Posts: 411

Hi All,


I have following Servlet.


When the very first request comes to this servlet. I got following results:

i am in constructor
init
doPost
service HTTP
service generic


I would like to know the reason behind last 2 outputs. I am confused how these two methods are getting executed.



Pawan Chopra
SCJP - DuMmIeS mInD
Balu Sadhasivam
Ranch Hand

Joined: Jan 01, 2009
Posts: 874


Pawan,



executes the last 2 lines. Remember doPost() is called by HTTP service method.
Ankit Garg
Sheriff

Joined: Aug 03, 2008
Posts: 9305
    
  17

If this code is just for experiment then its fine, otherwise in general refrain from overriding the service method. Override the doPost and/or doGet methods instead...


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Anirvan Majumdar
Ranch Hand

Joined: Feb 22, 2005
Posts: 261
The service(HttpServletRequest, HttpServletResponse) is the HTTP-specific version of the Servlet.service(javax.servlet.ServletRequest, javax.servlet.ServletResponse) method. Thus, when you make an HTTP request to your server, you get the HTTP service method invoked before the generic service method.
Ramkumar Subburaj
Ranch Hand

Joined: Sep 07, 2007
Posts: 83
The servlet life cycle is as follows.

1. Creates an Instance of the servlet class (Constructor)
2. Initializes the servlet (init method) and wait for requests.
3. if any request comes in, service method is called and this determines which type of request it is and calls the appropriate method(like doGet, doPost etc...)
4. The destroy method is called before removing the servlet from the container

I think you can trace what is happening by putting as the first line of the method definition and at the end of the method definition.


SCJP 1.5, SCWCD 1.4.
Hanging between Web Services and EJB
Ulf Dittmer
Marshal

Joined: Mar 22, 2005
Posts: 42289
    
  64
If this code is just for experiment then its fine, otherwise in general refrain from overriding the service method. Override the doPost and/or doGet methods instead...

+1. The service method doesn't need to be overwritten unless you're writing a servlet to handle HTTP extensions (which would be an exceedingly rare occasion).


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