Spring Boot Core Container and Beans 4

Question 1

What annotation is used to inject a value from application.properties into a Spring bean field?

Accepted Answer

@Value

Answer

@Value("${property.key}") reads the specified property from the environment and injects it into the annotated field.

Question 2

Which ApplicationContext implementation is best suited for a standalone Spring Boot application reading properties from the classpath?

Accepted Answer

AnnotationConfigApplicationContext

Answer

AnnotationConfigApplicationContext loads bean definitions from @Configuration classes without needing XML or a web server.

Question 3

What does Spring's @Qualifier annotation allow you to do?

Accepted Answer

Specify which bean to inject when multiple candidates exist

Answer

@Qualifier combined with @Autowired narrows the injection to the bean with the matching qualifier name.

Question 4

Which destroy callback runs when a singleton bean's ApplicationContext is closed?

Accepted Answer

@PreDestroy method

Answer

Methods annotated with @PreDestroy are called by Spring just before a singleton bean is destroyed during context shutdown.

Question 5

What is the effect of setting @Scope(proxyMode = ScopedProxyMode.TARGET_CLASS) on a request-scoped bean?

Accepted Answer

A CGLIB proxy is injected so the singleton can delegate to the correct request-scoped instance at runtime

Answer

A scoped proxy wraps the short-lived bean so singletons can hold a reference without capturing a stale instance.

Spring Boot Practice Test