The life cycle of a servlet is controlled by the container in which the servlet has been deployed. When a request is mapped to a servlet, the container performs the following steps.
If an instance of the servlet does not exist, the Web container
Invokes the service method, passing a request and response object. Service methods are discussed in the section Writing Service Methods (page 222).
If the container needs to remove the servlet, it finalizes the servlet by calling the servlet’s destroy method. Finalization ...