ServletContextListener is a interface which contains two methods:
When we implement any interface then we have to implement its all methods. This listener will help a application to start and shutdown the events.
How the ServletContextListener is useful:
1. ServletContextListener is notified when the context is initialized.
a). ServletContextListener gets the context init parameters from the ServletContext.
b). It stores the database connection as an attribute, so that the other components in the web application can access it.
2. It will be notified when the context is destroyed. It closes the database connection.
Recommend the tutorial