Before going into the details of ServletContextListener we should understand what is ServletContext. ServletContext is a interface which helps us to communicate with the servlet container. There is only one ServletContext for the entire web application and the components of the web application can share it. The information in the ServletContext will be common to all the components. Remember that each servlet will have its own ServletConfig. The ServetContext is created by the container when the web application is deployed and after that only the context is available to each servlet in the web application.
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.
The code of the program is given below:
The output of the program is given below: