Basically there are three life cycles of Servlet and are controlled by Web Container. Three Servlet Life cycle are 1. init() 2. Service() 3. destroy()
init() is internally called by the web container using servlet instance and is used to initialize ServletConfig with the parameter value if configured in the web.xml
service() is also called by the container when request is submitted to the server.
destroy() is also called by the container at the container shutdown.