16. What does the @Bean annotation do?
17. What is the default bean id if you only use @Bean? How can you override this?
18. Why are you not allowed to annotate a final class with @Configuration
19. How do you configure profiles? What are possible use cases where they might be useful?
20. Can you use @Bean together with @Profile?
21. Can you use @Component together with @Profile?
22. How many profiles can you have?
23. How do you inject scalar/literal values into Spring beans?
24. What is Spring Expression Language (SpEL for short)?
25. What is the Environment abstraction in Spring?
26. Where can properties in the environment come from – there are many sources for properties – check the documentation if not sure. Spring Boot adds even more.
27. What can you reference using SpEL?
28. What is the difference between $ and # in @Value expressions?
