Spring Core & Dependency Injection Flashcards

Which Spring annotation is used to read values from property files into fields?

Answer: @Value

@Value injects values from properties files, environment variables, or Spring Expression Language (SpEL) expressions into bean fields.

What does @Lazy do when applied to a Spring bean?

Answer: Delays bean initialization until it is first requested

@Lazy defers the creation of a singleton bean until it is first accessed rather than at container startup.

What Spring feature enables component scanning to detect annotated classes automatically?

Answer: @ComponentScan

@ComponentScan tells Spring to scan specified packages for classes annotated with @Component, @Service, @Repository, and @Controller.

What is the SpEL expression to access an environment variable named 'MY_VAR' in Spring?

Answer: @Value("${MY_VAR}")

The ${} syntax in @Value resolves property placeholder values including environment variables registered in Spring's Environment.

Which scope creates a new bean instance for every HTTP request?

Answer: request

The 'request' scope creates a new bean instance for each HTTP request and is only valid in a web-aware Spring ApplicationContext.

What annotation is used to register a method's return value as a Spring bean in a @Configuration class?

Answer: @Bean

@Bean is placed on methods inside @Configuration classes to indicate that the returned object should be registered as a bean in the Spring application context.