process of creating , invoking , destroying the servlet is
known as "life cycle of struts". here three methods are
involved 

1.init() :

Total intialization part of servlet ll be there in this .

2.service() :

Actual Bussiness code ll be there  in this method

3.destroy() :

just destroying the servlet  .

In life cycle of struts there r several part are there 

ActionServlet
Struts-config.xml
RequestProceser
formBean
Action class

There are many steps, 

1. After getting the request from the client, the 
ActionServlet invokes the goGet() or doPost() method, in 
which there is a invokation of process() method.This method 
desides the module.

2. Action servlet dispatches the request to RequestProcesor 
class which does some core works of ActionServlet.Then 
invokes the appropriate Action class.

3. Action class does main business logic and data accessing 
(communicating with Moedl) thru execute() method and which 
returns the ActionForward object.

4. In b/w the form field validations happens in form bean.

5. Depends upon the value of ActionForward object the view 
is decided to display.(output)


4. Form bean is invoked for form field validation,

The request is given to Action Servlet i.e; doGet or 
doPost.
ActionServlet with the help of request uri locates one of 
the RequestProcessor and dispatch the request to 
RequestProcessor i.e; process method on RequestProcessor is 
called InRequestProcessor.

It processes content type.
processes Locale.
processes actionPath.
processes actionMapping.
processes formBean.
processes action.
Error handling.

After processing action(i.e; execute method) depending on 
the results locate the path to view(with the help of 
ActionMapping) and dispatch the request to the located 
path.

When the Framework is loaded, it first loaded the Web.xml 
file. Then from the Servlet tag of Web.xml, it identifies 
the ActionServlet(or the Struts-Cofig.xml). Then from 
welcome-file tag of Struts-Cofig.xml, it identifies the 
first JSP page and runs it. Then when the request comes 
through that jsp, from acion-mappings tag of Struts-
Cofig.xml it identifies the request, through path tag
(request name) and input tag (jsp name), through name tag 
it identifies which bean is needed to access the data and 
through type tag it identifies which Action should be 
invoked. Then through the forward tag it identifies to 
which jsp it has to forward the response.

Sorry in the previous answer I made one mistake, welcome-
file-list is located in web.xml not in Struts-cofig.xml