-->first request comes from client browser to server 
  (container)which takes the control to the web.xml file.

-->in xml file servlet file(.class) will be searched
   according to the information about the url pattern given
   in the address,then coresponding class file is loaded to
   the container(loading) by the method
   java.lang.class.forName().newInstance.

-->now container call the init(servletConfig) method to add
   necessary headers in the servlet,such as Config,context
   session,request and many more.

-->now control pass to the service()of the HttpServlet(if   
   you have extended this class) and the type of method 
   (get/post) is checked and accordingly the control will
   pass to the implemented doGet() or doPost() of the your
   class(by the dynamic method dispatch)

-->after service the container will call the destroy() of
   Servlet class.
          i hope this answer will satishfy you,thank
          you,Dipu(Deepak ku. jenamani)

when we are requesting a particular resource in the
server,the comiled class will be loaded into the container
calls the no-arg constructor and init() then the container
will create request,response objects and pass it to the
corresponding doXXX() method based on the http method of the
form,allocates a thread and do the business logic and send
the response back to the client by sending the thread to a
connection pool and destroying the request and response objects

when we are requesting a particular resource in the
server,the comiled class will be loaded into the container
calls the no-arg constructor and init() then the container
will create request,response objects and pass it to the
corresponding doXXX() method based on the http method of the
form,allocates a thread and do the business logic and send
the response back to the client by sending the thread to a
connection pool and destroying the request and response objects