WebSphere Application Server - IBM Redbooks

Initial state
Figure 7-2 A servlet’s life cycle
Loading
Initialization
Service
handling
Destruction
Final state
All along its life, a servlet interacts closely with its container. Following the J2EE
specification, the container is in charge of providing a runtime execution for the
components. It is also responsible for handling a set of services such as
concurrency, administration, and security.
The servlet container is implied in all the steps through the servlet’s life cycle:
1. Loading: The servlet container uses a classloader to locate the class file of
the servlet and to instantiate it. This operation follows the Java class loading
process. An instance of the servlet class (and only one) is then available at
the end of this step.
2. Initialization: The container activates the servlet by calling one of its
methods, the init() method. The init() method must be implemented by a
servlet class. This method is called once by the container and is used to
initialize a set of parameters for the servlet instance. The servlet is then ready
to handle requests from clients.
3. Service handling: Each client request generates a call to the service() method
of the servlet class. This method can either generate the response and
transfer it to the Web server (via the servlet container) or dispatch the request
to another component within the container.
Chapter 7. Working with servlets 217