Which annotations does @SpringBootApplication combine?
It is a meta-annotation for configuration, auto-configuration and component scanning of its package.
QuizzesSpring Boot 4
Spring Core & Boot 4
DI, bean scopes, auto-configuration, configuration, AOP proxies, REST and what changed in Spring Boot 4.
16 questions
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Question 1 of 16Score 0
Which annotations does
What is the default scope of a Spring bean?
Singleton means one instance per container, not per JVM — two contexts can each hold one.
Why is constructor injection preferred over field injection?
Constructor injection produces complete, immutable objects that are trivially unit-testable — and it surfaces circular dependencies instead of hiding them.
Two beans implement PaymentGateway. Which does NOT resolve the ambiguity?
@Lazy only defers resolution — you still get NoUniqueBeanDefinitionException.
How does auto-configuration avoid overriding a bean you defined yourself?
Auto-configured beans back off when a bean of that type already exists.
Which property source has the HIGHEST precedence?
Command-line args beat system properties, which beat env vars, which beat config files.
Inside OrderService, importAll() calls this.save(), which is @Transactional. What happens?
Transactional behaviour lives in the proxy; self-invocation goes straight to the target object.
Which methods can a CGLIB-based Spring AOP proxy NOT intercept?
CGLIB overrides methods in a generated subclass, which is impossible for final or private methods.
In Spring Boot 4, what replaces @MockBean in tests?
@MockBean and @SpyBean were removed in Boot 4 in favour of Spring Framework’s @MockitoBean and @MockitoSpyBean.
Which JSON library does Spring Boot 4 use by default?
Boot 4 defaults to Jackson 3 (tools.jackson packages); annotations remain in com.fasterxml.jackson.annotation.
How does Spring Framework 7 support API versioning in controllers?
E.g. @GetMapping(path = "/{id}", version = "1.1") with the version read from a header, query param, path or media type.
Which client is the recommended synchronous HTTP client for new Spring Boot 4 servlet apps?
RestTemplate is in maintenance mode; RestClient is its fluent replacement (and HTTP service clients build on it).
What status code should a successful resource creation return?
Return 201 and point to the new resource with Location, e.g. ResponseEntity.created(uri).body(dto).
A request body fails @Valid validation. What does Spring MVC throw?
It is mapped to 400 Bad Request; handle it in a @RestControllerAdvice to return a ProblemDetail with field errors.
What does spring.threads.virtual.enabled=true do on Java 21+?
Blocking I/O code then scales like non-blocking code; downstream limits like the DB pool become the throttle.
Which annotations does Spring Framework 7 provide in core for resilience?
Enable them with @EnableResilientMethods. Circuit breakers still come from Resilience4j.
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