Spring

Spring DI

Component types (Service, Controller, Repository, etc.)
JDK proxy vs CGLib proxy vs AspectJ proxy
AspectJ compile time weaving vs runtime proxy
Why to use @Bean annotation? @Bean vs @Component
When do we need aliasing of beans in Spring?
@Autowired vs @Resource
@Qualifier in autowiring
Spring beans scopes, web scopes
Can we inject prototype into singleton? What is a lookup method or scoped proxy?
BeanFactoryPostProcessor vs BeanPostProcessor. What is the difference and when to use each of these?
How we can inject fields in Spring (xml, ctor injection, field and setter)
What is the difference between ctor injection and i.e. field injection (nulls not allowed in ctor injection)
What happens if i.e. beanA injects by ctor beanB and beanB injects beanA (so we have a cycle). Will the context start? How to fix such issue? (design issue but can be fixed by @Lazy)
What is a good use case for @Lazy? What is @Lazy?

Transactions in Spring

Transaction isolation in Spring. What phenomenas each isolation prevents?
Transaction propagation in Spring
How can we rollback a transaction?

Spring MVC

What is a dispatcher servlet? Describe the general architecture of Spring MVC.

Spring Boot

Describe what application servers are shipped with Spring Boot (or what servers we can use for). What are advantages of them?