12.
In a Java web application, what is the purpose of the `@ContextConfiguration` annotation?

13.
What is the primary role of the `ServletContextEvent` class in Java web applications?

15.
In Java EE applications, what is the purpose of the `@PersistenceContext` annotation?

16.
What does the `@Singleton` annotation indicate in Java EE applications?

17.
In Java web applications, what is the purpose of the `@RequestScoped` annotation?

18.
What is the purpose of the `@WebInitParam` annotation in a servlet declaration?

19.
In Java EE applications, what is the primary role of the `@MessageDriven` annotation?